Revisited: Want to Get Your Car Handling Better Than Ever Before? Listen to This.

Welcome to High Performance Academies, tuned in podcast, I'm Andre your host.

We'll be taking a break over the Christmas New Year period and we'll be back in action

mid January. That means that although there won't be any new episodes

for a few weeks, we'll be taking another look at some of our favourite episodes.

This week we're going back to episode 100 featuring Bruno Finco from Optimum G.

Now Optimum G is a name that I've been aware of basically

since I got involved in the automotive industry. If you haven't heard of the name

you'll find out exactly what they do as we get into our interview but essentially

they offer software packages for analysing and optimising all facets

of race car performance. They also do consulting work for OE manufacturers

as well as high end race teams and they run training seminars.

Now from the outside I'd always assume that essentially you'd need a PhD

in order to be able to use the software products that Optimum G provides

or alternatively get involved in one of their seminars. While their topic

content is quite deep and vehicle dynamics is a complex topic in and of

itself, you'll find out as we go through this interview with Bruno that no,

you absolutely don't need a PhD. This is a really interesting topic

as well because prior to reaching out to Bruno to get him on the podcast

we actually had the opportunity to use some of Optimum G's software packages

around the development of the suspension on our Honda CRX.

And while initially it looks complex, it's actually not very difficult to use

and once we dived into it we found how powerful this software is.

This is a really deep dive into the world of vehicle dynamics

and suspension kinematics and all of this really is just about optimising

the tyre contact patch with the racetrack surface. Obviously

no matter what car we've got and how much power it's got, as well as how much money

has been poured into development, ultimately the performance of every car is

limited to that tyre contact patch so we absolutely want to make

the most of it. I also use this as an opportunity to really

pick Bruno's brains for my own benefit and hopefully everyone listening is going

to benefit from that discussion as well. We get deep into the weeds in this

conversation with some of the less obvious or less well known terms

around suspension design and suspension kinematics, such as roll centre,

roll centre heights, roll centre gradient, front to rear roll centre

migration and how these elements affect the handling, performance and balance

of the car. We also dive into Ackerman steering and what that

term means and how this can be used as well to help improve the performance

of the car. We also cover subjects such as anti-dive and anti-squat.

So this is going to be a very interesting chat for those who want to understand

suspension kinematics and vehicle dynamics of their own car more intently

and of course we also cover the various software packages that are available from

Optimum G and how they can be used. And again the fact that you don't need

a PhD in order to be able to use them. So let's get into our

interview now. Alright welcome to the podcast Bruno, thanks for joining us

today and for a start where are you joining us from in the world? I am in Brazil currently

so I'm Brazilian and I have recently moved back here. Okay, where is

Optimum G based? In Denver, Colorado, United States. So I lived there

for a couple of years that I moved to Europe because most of my projects

are in Europe and I'm finally back in Brazil travelling a lot but

yeah it's a little bit taller over the place. Okay, alright well let's roll things back

a little bit and I'm interested to learn a little bit about your background and specifically

how you developed an interest in cars and more the high level

sort of engineering aspect of the automotive scene. Right, so

actually I'm not the typical car guy that liked cars as a kid

I just knew that I wanted to be an engineer but no particular interesting cars

so I went down to studying mechatronics engineering

at University of São Paulo and there we have the

Formula Student or Formula SE project. Are you aware of the project?

Yeah absolutely, I think probably must have been about 30 to 40%

of our guests so far bring up Formula SA and every time it comes up

I get jealous because I never had that opportunity here in New Zealand

universities but give us a quick rundown for those who maybe haven't followed the podcast

or don't know what it is. Yeah so it's basically we as students

we design race cars from scratch, we build it and we race it

and by the way it was one of the drivers so I think you can be even more jealous

now and then we compete with different universities

so here in Brazil we had another 40 universities to compete

with our race car, we then won the competition, we went to the US

competed against another 140 universities from around the US

which was pretty fun and I simply fell in love with race

cars with VCO Dynamics with applying everything that I was learning

directly to this project to make a car faster and this is how I decided

that I wanted to work in this area. Actually all became

concrete once Claude Ruel, my current boss owner of Optimungi came to

Brazil to teach a seminar in VCO Dynamics. Once I was done with a seminar

I decided to think it was number one that yes I wanted to work with VCO Dynamics in race cars

and number two that I wanted to work for Optimungi and

yes so I applied for the company, I got the position

even before I graduated, had to rush to graduate as soon as possible

moved to the US and here I am today. Okay so straight out of

your degree and straight into Optimungi so again just

clarify the degree that you qualified out of University with was

Mechatronics Engineering which is basically to work with robots or robotics

in general and now I apply that to cars. So quite

removed from the specifics around vehicle dynamics but I'm

guessing there must be some crossover in there. Yes there is but I think

it's a very good example because so many people tell me I don't have an automotive

degree in my school, I don't have any VCO Dynamics courses, guess what I didn't

have any whatsoever and I never had any classes. I think in VCO Dynamics

or automotive I think the first one was really the seminar from

Claude in Brazil but you have nowadays you have so much material, books,

YouTube channels and so on that you don't need that so yeah.

We have a lot of engineers come through the podcast

and I think if you've got a basically any

university is going to offer some kind of mechanical engineering degree and that is

a very very broad topic, it's not necessarily

centered solely on the automotive field but once you

understand those concepts they can be applied to a specific field

like vehicle dynamics. Absolutely so whenever I'm studying vehicle

dynamics I'm applying the physics and mechanical engineering concepts that I learned in school.

Sure so the passion for applying

what you were doing in university into the automotive field

and then taking this vehicle dynamics seminar with Optimum G

am I right in assuming this is sort of born out of your formula SAE work? Yes

100% so I was the head and lead of suspension and vehicle

dynamics and after that I became the lead of testing and

data analysis so it all started there. Okay excellent

alright so let's talk a little bit about Optimum G

and what it is so give us a high level

overview of what Optimum G actually encompasses. So

Optimum G is the vehicle dynamics consultant so basically we offer solutions

involving vehicle dynamics we have three main offerings number one

is consulting in which it could be as a race or performance or data

engineer at the track with our customers or it could be different projects we have

manufacturers hire us to help them develop better tires to match the vehicles

we have race car designers hiring us to design their suspensions and so on

besides that we also offer simulation

software in the fields of kinematics tires and vehicle dynamics

and lastly we teach seminars all around the world two main ones

vehicle dynamics and also performance engineering. So this

really connects with my trajectory at Optimum G now I am

the lead performance engineer so I am one of the engineers going to the track

and coordinating our motorsport activities and I'm also the head of

consulting so I'm leading most of our consulting projects organizing our team

and so on. I also teach some of the seminars together with Claude

another colleague of mine so different seminars are taught by different

designers and it always started now it connects to software it always started

with me as one of the software developers so this is how I joined the company

and then I was moving more and more to the consulting and track

performance aspects which is what I'm really passionate about. Okay now we're going to

dive into those offerings that you've just talked about in a little bit more detail

as we go I'm interested with such a unique

position what's it the day in the life of Bruno currently look like

it's pretty fun to this party I really enjoy it so basically

either I'm traveling for consulting projects or for races so

now I live in Brazil but I'm traveling to Europe let's say every month for the races or

for projects so when I'm in the field I mean it's work the whole time

weekends no days off whatsoever going to the track since the races

on a weekend but very enjoyable meeting lots of different people

lots of different customers now when I'm at home running the other consulting projects

my day looks like wake up early in the morning go to the gym

I try to go to the gym every day then I come back to several meetings

in the morning so I try to run what we call daily meetings it's difficult in terms of

engineering processes that you have daily meetings so that everybody can update

or can give the updates on the different consulting projects that we're running that lunch

and in the afternoon I try to have one hour call with several members of

our team so let's say that we are working in testing a tire for one of

our customers in the rigging the flat track then I'm going to have one hour

calling the afternoon to review okay so how is the procedure that we're developing going

how are the tools that we're developing going so I try to do that until late

afternoon and then I have the night to perform the work that I have to do because in the

consulting projects I also have to do some work and as you're going to notice

very quickly I love learning so I try to also reserve a couple of hours

at the end of the day to keep learning for upcoming projects so that's what

I pretty much do. That sounds like you're packing a lot into the day good

on you can you give us some insight into maybe

what some of these consulting projects are I'm sure there's a whole bunch of NDAs involved

but I mean are you dealing with individual teams

you know maybe running a GT car or something like that or are you working

at OE levels with manufacturers building bespoke

race cars all of the above? Great question yeah pretty much all of the above but

let me even though I cannot give you names I can give you some very good examples of the current

projects that I'm running but okay so we work with specific teams

we obviously work with only one team per championship we don't work with two different

teams but I have a couple of performance engineers work with me so

we are currently doing GT World Challenge Europe we are doing DTM

so we are leading the championship in GT World Challenge we're doing pretty good in DTM as well

and we worked in Formula E even though the season ended now so these are the three

championships that we are most working actively this year and I'm coordinating

some of them with my performance engineers of the track besides that earlier this

year we had a race car manufacturer hire us to design their suspension

which is pretty nice because the car is now hitting the track and we

can see how the design will really behave at the track besides that

we have racing teams hiring us to test their tires in the flat track

so in the laboratory you have a huge machine that you can mount

a tire and test that and we also work with tire manufacturers so we are

developing new tires for future championships so I go to the track with

them so that I am the VCO Dynamics and Data Analysis

engineer for them so they're working on the tire side I'm working on the VCO

Dynamics and VCO performance side so I'm processing all of the data generating

KPIs, metrics and helping them to improve their tires for the following seasons

and lastly we also work with OEM so not only racing

but we also do OEMs so we are working in projects connecting

tire performance with the equal performance helping them design better

and safer cars. It's a massive list you've just given us and

it's great because it does obviously give us immediate insight into the level you're working at

and what you're doing. I'm interested particularly when we look at some of the

larger teams or specifically when we get to the OE level, obviously

the OE level money within reason is not an object, I'm interested

in why they would not look at having an

in-house resource to offer the services you do rather than

using an external consultant. Yeah that's a very appropriate question because

it is one of the challenges that we face because many people they want to build their own

teams so while there are two answers to that many times Optimum G

is at a higher level than they are and they don't have the time to build a team and they need

quick results so they are hiring us. Sometimes is

a one-off let's say okay so a racing team needs to

perform a tire performance analysis test different tires they don't need to build a team for that

they hire Optimum G and we solve all of their problems and one

thing that I would say it's an advantage of Optimum G compared to other

consultants that we are happy to share our knowledge so sometimes

our customers also hire us first to train them on how to perform such

job so that in the future they don't depend on us anymore.

So yeah there are a couple of different reasons why they would work with a consultant

compared to building an internal team for that work. Okay yeah that

makes perfect sense. I guess so far we've talked about some fairly

high level concepts and we're going to go deeper down this rabbit hole but before we

sort of scare off half of the listeners could you give us an idea

of who could benefit from Optimum G's

seminars and software I mean do you have to be a professional

racing team or an OE manufacturer to get value out of this

is a grassroots racer or a club level racer

able to get value? Oh yes so what happens that when we offer

direct consultant services to someone typically it's at the professional level

just because of the cost it's hard for an amateur driver

to justify the cost even though I have worked with some for example helping them

fine tune suspension stiffness them being driving analysis, data analysis

and so on. However a lot of our products are also

very very useful for this type of racing such

as Optimum Kinematics which helps you build and design a better suspension

such as Optimum Lat which helps you understand the performance of the car

and what tradeoffs you should do in terms of power, training and mass. Our seminars

are a great source especially if someone who is learning, who is improving

and who wants to keep growing it's certainly very good option

as well but it's interesting Andrew because in our seminars it's not only professional

motorsport engineers we have many students so first or second year of engineering

school they're already in our seminars so as long as the person prepares

for the seminar and has some understanding of vehicle dynamics they're going to

get a lot of knowledge out of them. Yeah okay good to get that clarity

I mean one thing I'll add in here which is one of the reasons we're talking

today is that we internally used

Optimum Kinematics on our Honda CRX project and I'll probably go into

a bit more detail in how that worked as we go and to be absolutely clear

no one inside of HPA, I work class as a rocket scientist

there's no one with a PhD, we I think

most of my guys, the guys particularly who are using that software

they learn to use it over the course of a couple of days and they're just

average smart people so I want to make that really clear that

you don't have to have a PhD in order to gain value out of it.

One of the things that I just wanted to talk about here with your seminars is

a catchphrase on your website, learn more in four days than a two year master's degree

so give us some background around that, how do you pack

that in in four days more than what someone's going to get in a two year master's degree?

Right so actually this phrase came from many

people telling us so it's not, we didn't come up with it, we had

many multiple people telling us I learned more about

vehicle dynamics specifically of course in your seminar than I did

in my master, well for sure it's a good thing for us, I'm not sure

it's such a good thing for a master's degree but in many case they're

not focusing as much on vehicle dynamics at least not to the

extent that we would consider acceptable and I would add another thing

they're not necessarily as concerned about how applicable that knowledge

is, why we are, we are discussing setup changes, we're discussing how do

we make a car faster based on that so of course there are many master's

degree with excellent vehicle dynamics courses but oftentimes

we hear that they're not as good so this is why we have this

phrase just because we heard from multiple people and how do we do that? Well

our seminars are pretty long even though it's only four days it's almost 12 hours a day

so it goes from 8am to 8pm so in the end it's 46 hours

okay you have lunch, one hour you have a couple of breaks let's say 40

no sorry 42 hours or 40 hours which is a lot of content

like if you stop to think about it, if you have one hour per

one or two hours per week how many weeks will take you to come to 40

hours of max content? Our material has been developed

for the past since the company started so for the past 25 years we have

been fine tuning our vehicle dynamics seminars so we just found the most efficient

way of presenting this information so that people can make use of

the knowledge so it's not a binder or a book that you

read and then you have no idea what to do with that every part of the project

there was a specific section that I would come back and just revisit the equations, revisit

the concepts and then improve my car based on that so I think that's basically

how we do it and our teachers are very good so Claude is an excellent teacher

I don't know if you had the chance to come to any of our seminars ever? I have not

I have not. Okay Claude is an excellent teacher extremely efficient

and I think that me and my other performance engineer we just

expected from him so we can teach him a very efficient way to give so much

content but in a digestible way so that people can really understand

and retain this knowledge. Okay now you mentioned

that you've had professional engineers come through and do your seminars

and also students I'm going to guess here that there is

a base level of mechanical knowledge as well

as a base level of mathematical knowledge that's going to be

required before you would take one of these courses is that a safe

assumption or am I off the mark there? Right yes you don't have to be

a genius but you have to have some understanding of physics and

mathematics. In many cases you don't even need universal level physics

many times just high school level if you master the basic

physics laws and forces and so on

it's enough to understand the physics concepts in terms of mathematics yes

some skills but I think more than that is just understanding engineering

concepts in general if you learn it from school high school or by

yourself and I would say some vehicle dynamics background is very useful

so whoever is asking me how should I prepare for the seminar can I come

without studying anything I would say it's not the best use of your time because you're not going to

be able to retain as much however if you study

some vehicle dynamics ahead of time I actually have I'm going to

give you the link for that later but on my Instagram I suggest all the vehicle dynamics books that

you should study in which order if you do like the first one or two

then you have a very good background to make the best use of the seminar

and retain as much of the information as you can. Okay now that sounds

good and it's always nice to have those resources as well for our listeners to be able to

get into. Okay let's dive a little bit more into

the software you've already mentioned the various software packages that Optimum G

produces but again could you just reiterate those? Yes absolutely

so we do we developed Optimum Kinematics which helps you understand

and design the kinematics of your car then we have Optimum Tire

in which you can get tire data and you can fit models

or understand the tire models that are more and more commonly used in vehicle

dynamic simulations and then we also and by the way we just

released a completely rebuild of Optimum Tire which is called

Optimum Tire 2 which is an amazing software really you can talk a little bit about that if you want

and then lastly we have Optimum Lap so Optimum Lap is very

interesting because it's a very simplified software but even professional

racing teams use it because it is useful so we selected

what are the most important parameters in car controls and

you only have them as inputs so you have mass, you have

downforce, you have engine power and engine curves or torque curves

and you also have gear ratios and you have tire grip and with that

you can also model the track and then you can simulate your vehicle and then

you can quantify right so if I change my car

and I add 100 kilos how much lap time am I going to lose

or if I increase the power by 10% how much lap time am I going to gain

and this gives you very quickly disasters but it's so nice to see

the most amateur driver just enthusiast playing

with the software just to learn how race cars work, how race car performance

works and then you go all the way up to professional motorsport engineers

using the software because it's just a very good way to give you

the fundamentals and the answers that you want.

We'll dive into that one in a moment and we've used that software

in the past to help choose gear ratios in the Hollinger gearbox

that went into our SR86 endurance car.

Before we get into that though let's just come back to the optimum kinematics

at the start and we've again used this software in

house and found it to be exceptionally powerful

and exceptionally valuable and the reason I say it's exceptionally

valuable is in our case it saved us wasting hours

and hours, probably weeks of time not to mention the cost of the materials

that would have gone into the modifications we're making so to give the very brief

story here we've got our Honda CRX powered by a naturally aspirated K20

2L engine and what we wanted to do was move the

engine back in the engine bay, I won't go too deep into why it was mounted

where it was but we basically could move the engine back about 100mm

which seemed like a great idea and we got into

the changes that would be required to do that, we needed a

chromoly subframe to mount the engine and the lower control arms but that was fine.

The problem we struck was that by

moving the engine back we had to completely relocate the steering rack

and when we relocated the steering rack we modeled

the suspension kinematics and optimum kinematics and we very quickly

found out that we were going to have a completely unmanageable

bump steer, like the car would have been an absolute pig to drive

at downright dangerous so obviously a complete step in the wrong direction

and once we saw this we went back and thought okay well

let's see for a start, what was our baseline? So we modeled

the factory pickup points and looked at the bump curve or the tow curve

as a result of that and I mean it might surprise some people I think would assume

that properly designed suspension has zero tow change

through bump and rebound and that's probably not realistic

so there was some tow change anyway with the factory suspension

but we were just so far out of the ballpark it was ridiculous

so then we started looking at modelling some options and we could fix it

by mounting the steering rack through the middle of the front differential

which obviously is not very realistic or we could have extended

the steering arm out so that it sat in the middle of the wheel and the tire

which of course again is unrealistic so straight away you're like well we're boxed into this

we can't do it, it will not work. And if we had gone

through the process of moving that engine back, making the subframe, mounting

the suspension, God forbid just taking the car to the track and trying driving

it would have been a disaster so that's just one

aspect of saving us time not to mention actually going down the path

of looking at various iterations of suspension, design and seeing

where you can get improvements so that's my experience with it and like I say

I mean my guys who did that work didn't find it very

difficult to build up the knowledge to use the software properly.

Let's come back one step though, we've used this term kinematics

what's it actually mean, what is suspension kinematics?

Right so basically suspension kinematics is defining the wheel movement

as well as a few other parameters such as road centres that control

low transfer. Alright so when you compress the wheel it goes up

and down, the camber is changing, this is kinematics, the caster

is changing, the toe is changing, when you roll your toe is also changing

all of that is kinematics. It is extremely important to understand what's

going on because we know that in the end everything is about tire performance

it's the only thing really generating force to move the car

from one turn to another to accelerate the car and so on. So we are trying to

optimize the use of the tire and you can only optimize the use of the tire

by designing good kinematics and good motion and movement of your wheels.

So that's basically it and what the software tries to do is to

simplify it and actually it's what everybody tells us it's very user friendly

very simple to work with but it provides you an easy platform

for you to model your suspension and then focus on these movements

you can move your car up and down in simulation and understand

what's going on with the camber, what's going on with the toe, what's going on with the

instant fanners, roast fanners and so on. So this is one of the stages

it allows you to analyze your current suspension. The second stage it allows you to

optimize the suspension and I don't know if you have played with it or if you guys have

but we have now the optimization module which you basically tell the

software I want this bump steer, I want this alignment variation as I compress

the tire and the software can tell you all right if you want this curve your pickup

point should be up here or this other pickup point should be a little bit more forward

so this would be from the design perspective you can both

analyze your suspension or it can help you better design your suspension.

One last aspect is that with the forces module you can apply forces in a

concrete patch let's say we're cornering at 1g you want to know how much

or what's the stress in each of your components the software can also

calculate that for you so when you make a modification to your suspension you can

understand how much more load you are getting because of this notification.

That in and of itself is a really interesting point because we've had

guests on the podcast previously who are involved

in designing and manufacturing components usually via

CNC for example or the 3D modeling process and we've talked

about FEA in that instance and how we can use that

to confirm that the part is going to be fit for purpose basically

will support the loads involved but the question there always comes

back to well that's all well and good but to use FEA you have to tell

the software what the loads are going to be, what the forces are going to be.

If you don't know those, how do you estimate those so well now we know

Optimum G or Optimum Kinematics will allow that so that's really

interesting. In terms of the software pickup points,

the suspension pickup points though I'm guessing probably a few listeners

are thinking to themselves right now, well that's all well and good but how on earth

do I accurately define these points because just like the FEA that I mentioned,

this is very much a case of garbage in, garbage out.

If we don't accurately have the suspension pickup points located

as far as the Kinematics software goes, all bets are off.

Now when we did this with our CRX we've got the benefit

of having a 3D scanner in house so the whole

front end of the car is scanned and we've basically

been able to build the car in the virtual world using Fusion 360. I'm absolutely

aware that not everyone listening is going to have the benefit of a

$10,000 or $15,000 laser scanner on hand so can you give us some

ideas on what the options are in defining these pickup points?

Right so from our side we have a couple of different options. Sometimes

when we work with the car manufacturer then we get the pickup points ourselves, that's the easiest.

Then we have the lab casting such as the ones that you guys used

such as 3D scanning and you also have the 3D arms so you basically

mount the chassis and then you have a 3D arm that is able to measure the pickup

points and tell you the exact location. These are the most accurate

and then you have the not accurate necessarily but more creative

ways that people they definitely find ways to measure that. So in that

case you need your chassis mounted to a specific

location but completely stable. Then you need to create

some references let's say the front axle or the middle of the front axle

is your reference. Then you have to split the measurements into different parts.

You need to measure the lateral coordinate which we call the Y

then you need to measure the longitudinal coordinate of this pickup point. How do you do that?

Well the easiest is to do on the ground because it is flat

so what you could do is you could hang a rope

with a short weight or with a little weight

and then you can measure the lateral coordinate and the longitudinal coordinate

of the pickup point and then the height is not that difficult. You can just

take the measurement of the height of the pickup point and in that case you would

have the pickup point location in 3D that you need

for the software. Of course you're going to face many challenges because the bottom pickup points are

easy to be measured or at least easier. The upper ones you

could have some other parts even the chassis on the way so you're

going to have to be a little creative to calculate offsets and then to come up with

new references to measure those pickup points but we have a couple different people

doing the measurements themselves. Yeah I'm glad you mentioned that there are

alternatives albeit you're going to have to get a little creative. It's going to take a little bit

more time and I think it's fair to say if you're using the

weight in a string I was going to call it a plumb bob which is a term

that I think a lot of people will probably recognise. Accuracy, I mean it's probably not

going to be the same as our PL3D laser scanner which is probably going to be

plus and minus, maybe 0.1 of a millimetre, I'm guessing with a plumb bob.

You're probably going to be within plus and minus 2 millimetres but you know you do the best that you can

and it's going to still be beneficial. There's going to be

a fair bit of work setting this up initially but once you're done

then you can move into the software. Alright so

with the Optimum Kinematics software there's a range

of terms that come into this and I kind of just wanted to talk through

some of these terms with you so that our listeners can get a really

good idea of what the relevance of these terms are and how they actually

affect the handling or the balance of the car. So one of the first ones I want to talk about

is roll centre and specifically roll centre height. This is a

term that we hear very frequently when we're talking about vehicle dynamics

so for a start what is the roll centre height?

It's good to discuss that because there's so much misconception around

this concept. So the roll centre height or roll centre

as the name says it's the point around which the chest is rolls

when it is rolling. So let's say that we're taking a corner

the car is going to roll around the specific point of the suspension, this is called the roll centre.

In this case this point is coming from

the instant centre. So your left suspension will define

one instant centre which is the point around which this left suspension

rolls or moves around. So the left suspension is defining

the instant centre, the right suspension is defining the instant centre. When you connect

both of them then you have the point around which the chest is

rotating. This is one of the definitions but

it's a simplification. So in reality the car is not rolling

or rotating about that point but it's a good way to

understand the concept of roll centre. However there is another

in my opinion even more important parameter defined by the roll

centre which is important for everybody working in terms of vehicle dynamics

car performance or even car builds which is load transfer. We know

that when we take a corner let's say a left hand corner we're going to have a lot of the

load or the weight being transferred from the left side to

the right side. A lot of it is going to go through the springs. This is why

the car rolls because it needs to compress the spring on the right side while extending

the other. However it's not all of the load transfer that is going

through the springs. A lot of it is also going

through the wishbones and through the links. So let's say that you are

transferring 300 kilos. It could be that 150 kilos are going

through the springs but 150 kilos are being transferred through the wishbones and through

the links. Increasing the load on these links and you could even

get some failure on these links because of this load transfer.

So the first one through the springs is called elastic load transfer

because the spring is an elastic component. The second part of

it is called geometric weight transfer and this geometric

weight transfer is defined by the roll centre height. So if you have a really

high roll centre most of the load transfer is going to go

through the wishbones and the links. The advantage being the car rolls

less. It's a little more stable. The platform is more stable.

The disadvantage being you have a lot more stress on these components

and you risk breaking them. So if you design a suspension and you make

a modification and you increase the height of the roll centre

but you don't design your parts appropriately for that extra load

you can get suspension failures because of that.

Yeah I think that would be something that could be quite easily overlooked

as well. Now you also mentioned another term there, centre

of gravity. There's a relationship here between the height of the centre

of gravity and the height of the roll centre that is going to also

impact the way the car will roll in a quarter. Can you

give us an overview of that please? Absolutely. So the most

important parameter is not the roll centre itself. It's the percentage

of the roll centre height compared to the CG height. So

if you have your, let's say your roll, your CG height

at 400mm and your roll centre height at

200, you can see that it's 50%. Therefore 50%

of the load transfer is elastic going through the springs

and the other 50% is geometric going through the

wishbones and links. Now my question back to you, Andres

what happens if I have my roll centre height at the same height

as the CG? What's the proportion between elastic versus geometric

lateral roll transfer? You're really putting me on the spot here. You know that you're

the guest, not me. However, my understanding

is if we've got the roll centre height at the same

height as the centre of gravity, the car should not roll in the corner, is that correct?

Perfect. And why it's not rolling? It's because all of the load

transfer is not going through the springs, but instead going through

the wishbones. So you see that everything connects. So yes, you have the lateral

acceleration being applied at the CG, but if the point around which

you rotate is at the same point, it's not going to roll. But in the end, it's all

because the load transfer is going through the wishbones and through the links, not through the spring.

So you see that everything is connected. The first concept is connected to the second

concept. These are all quite complex concepts for

particularly those who have maybe never heard of them before. So I think it's probably

one of these podcast episodes that's going to benefit from people reviewing

and going and having another couple of lessons until everything clicks into place.

On that same note there, if we go to the other extreme and the

roll centre height was actually above the centre of gravity height, the car would

actually roll into the corner, which I mean sounds probably beneficial

but the reality is if you went that way, that's not what we want to achieve, right?

Right. But yeah, you're absolutely right. So you have the opposite

behaviour because you have the lateral acceleration below

the point around which you rotate. So you rotate or basically you roll

in the opposite direction. However, it does not mean that the load

transfer is going to go in the opposite direction. The load transfer can only go to the

outside tyre. It's only the suspension that is rolling the opposite

direction. Now what we're talking about this roll centre height versus centre of gravity

height, the other element that I just want to bring in here which is a misconception

I guess in the enthusiast market is we lower the car and

the handling is going to improve. And I think that's something that everyone

getting into cars and looking at the ride height of the current crop

of GT3 race cars would just assume, lower

ride height, better handling. But the reality is that

some interesting things actually happen, depending on your suspension geometry

to that roll centre height versus the centre of gravity height when we lower

a car. So can you talk about some of the nasty things when the geometry

isn't correct and what happens to that roll centre height versus centre of gravity?

So let's say that you lower your car. You're not just taking

the chassis lowering it and the suspension is staying in the same position. The suspension

is also moving. So all your kinematics parameters are changing

when you lower your car. In this case, why the performance

improves? Well, if it's an aero car, it's obvious it's because you get

more ground effect. If it's a non aero car, the biggest factor

in improving car performance is because you lower the CG. If you lower the CG

you transfer less load when you are cornering and you have a more stable

platform, more well distributed load on all four contact patches

of the tires. However, as you all mentioned, you should also be aware

of what's going on with the kinematics when you lower the car because your roll

centres will also change height, typically going

lower. This means that you're going to lower how much

geometric weight transfer you have and you're going to increase the

elastic weight transfer to the springs. Well, what's the difference? If you have

the load transfer through the springs, it is lower because you see that

the car needs to roll first before taking effect into the corner.

When you have a lot of geometric, it's an instantaneous load transfer

so the car is a lot more reactive. You just have to be mindful

that when you change the height of the car, yes, you are lowering the CG, that is excellent

and it's one of the primary factors in car performance. However,

you are also changing how quickly you're going to transfer this load, depending on

what you've done to your roll centres. Not only that, it could happen that

you are changing more than one axle than the other, so you are changing how quickly

you transfer the load on the front. Let's say you make it faster on the front but lower on

the rear, so this could also influence the handling of your car. So it's

just very useful when you can understand what's going on in terms of your

roll centre heights when you make such a big change to your right heights.

It's one of the problems we see with more production based cars when they're lowered

and all things being equal, McPherson Strutt

front suspension is probably the go-to for most OE manufacturers

for garden variety cars because it's easy to package

and relatively cost effective to produce. And the problem with that is as we lower

a McPherson Strutt suspension, generally what was a couple of problems there, one

is what happens to the camber. Maybe we'll park that element and come back to that

shortly but generally the roll centre is going to lower much more

than the centre of gravity lowers. So you've sort of got this

moment arm I guess between the roll centre height and the centre of gravity so the car

tends to roll more and that's why there is also a range of

correction products for popular cars, for roll centre correction

and bump steer correction to kind of get that, the kinematics back where

close to where they were but with the lowered ride height and the lower centre of gravity.

The other element you just mentioned there is the rear roll centre height so

we've talked currently about one axle line on its

own but we've obviously got a front and rear axle both with their own

suspension kinematics and both of course then with their own roll centre

heights. So then if we're looking at the car sideways we can actually draw a line

through the front and rear roll centre and get a gradient so they're

not always going to be at the same height. What's the importance of

that gradient and is that a tuning tool we can use to help

with the car balance and handling? Yes that is for sure so one thing

that people like to do that I do not personally like is to create a roll

this should be your gradient, this should be the inclination of what we call

the roll axis which is basically connecting both

roll centres. Typically for race cars or most of the time

we have the front roll centre lower and the rear roll centre

higher. However what I always like to emphasize

for people is that there's so many parameters influenced in car performance

that it's not that if you change a little bit this rule of thumb that

typically the typical race cars use that you cannot get good balance.

I mean you can play with strings, you can play with engine bars, you can play with adjustment

to make up or to change that behaviour. In any case

it is an adjustment tool because if you change the roll centre

of only one axle you are influencing a lot the low transfer

on that axle. So let's say that you decide that okay let's say that

you have too much understeer which is typical for passenger cars.

What could we do on the front axle? We want to decrease

the low transfer because we know that if you decrease the low transfer on that axle we get

a more efficient tire usage. To decrease the low transfer what can you

do? You could soften your bars, you could soften your strings but then you're going to

start getting more movement or you could lower the roll centre height.

If you lower the roll centre height you're going to get less

low transfer on the front axle. And then as a consequence

I'm not going to go into the details, you end up increasing a little bit the low transfer

on the rear axle. But what do we get? Now we get a more balanced car because

initially it was understeer. Now we were able to change the kinematics

to influence the amount of low transfer on the front axle. We decreased it,

we made the front axle a little more stable, a little bit more efficient and now

we have less understeer. So this is how you play with this gradient or

the roll axis in order to influence car behaviour. So it's all about

what's the change that you make to the front compared to the rear. This is why

I mentioned when you lower your car, it is very interesting if you understand

what's going on with the front also compared to the rear.

Now you've just talked about making that change at the front axle. Am I right to assume

that you could make an opposite change and increase the low transfer on the rear axle

and have the same overall effect for the handling balance?

You're partially right. This is another typical misconception of Eco Dynamics that I tackle

so much or Optimum Gene in general which is if you change the low transfer

on one axle, you cannot lower the total low transfer of the car.

You can only lower the total low transfer of the car if you

change the CG, if you change the lateral acceleration and you don't want to decrease

the lateral acceleration, you want to increase it, you could decrease the mass or you

could decrease the wheel track. Unless you play with one of these four factors

you cannot change the total low transfer that your car sees when it's

attacking a corner. These are just the roles of physics, right? Yes, exactly.

The only thing you can do is to change the distribution of how much this total low

transfer happens on the front axle compared to the rear axle.

This is one of the most important parameters defining mechanical balance.

If you have under sear or over sear, one of the first questions we ask is, how can

we change the low transfer? As you mentioned, we could lower the

front CG to decrease the low transfer and it would automatically increase

the low transfer on the rear. Remember, it's all about the distribution.

Or conversely, we could do what you just proposed, we could

increase the height of the rear roll center to increase the low

transfer on the rear which would automatically decrease the low transfer on the front.

And these would be, at least in simplified terms, they would be equivalent

solutions to combat this under sear and lateral acceleration. Just the reason I wanted

to bring up that option is obviously it's nice

if there's a way of quickly and easily making a handling balance change

during a pit stop. And just a race series that I was involved with here

in New Zealand many years ago, it was a front engine rear wheel drive

race car production based with a solid or live rear axle.

And the mechanics had access to a screw adjuster

through the rear deck lid and basically in a matter of seconds

they could wind that up or down and make a subtle change to the roll center

height at the rear. You couldn't easily make that same change at the front

but that was an effective way of making a handling balance change

very, very quickly while the other mechanics were maybe

refuelling or changing tires so that's just something I wanted to point

out there. At the moment we've discussed this roll center

location and kind of treated it like it's a fixed point but

the reality is that it is going to move around depending again

on your suspension, geometry, kinematics, etc. So

we're trying to design suspension that keeps

that roll center as close to one point as we can.

How much does the migration of that roll center during

heave and roll of the race car actually affect the balance?

That's a very good question because you find pretty much no material

explaining the matter on the internet, at least it's very hard to find.

But basically yes, as you were saying, once you brake into a quarter, once you quarter

you're compressing and extending your suspension, you're moving your

suspension which is changing the kinematics. So as you mentioned, the roll center will be

migrating. It could be going up, it could be going down, or it could be

moving sideways to the left and to the right. So you know that

it is always easier to understand a problem if we simplify it.

In this case, what suspension design

would be easier to understand? One where the roll center is not

moving a lot. This is one of the reasons that we try to keep under

control because then we can better understand what's going on. We don't

have surprises that the roll center moves so much sideways now

the suspension behavior is completely different. So this is the main reason why I personally try

to keep under control just to simplify the problem. The second consideration

let's speak about roll center height. One thing that we need to understand is the following.

Once the car goes up and down, especially if you make right height adjustments

or if it's an arrow car that at high speeds is sitting at

much lower right height than at lower speeds, it is important

to understand how much your front roll center is going down proportionately to the rear.

Are they moving the same amount or is the front moving three times more than the rear

for example? And you gave some examples where this is very important.

So this explains up and down. If it goes up and down, it's all that we

discussed now. If the front is going down, it's going to induce more or less understeer.

If the rear is going down, it's going to induce less oversteer and so on.

In any case, so this is the easy part because we already discussed that.

Now the question is what happens when the roll center is moving sideways?

Well, to explain all the details, it will go back

to physics and to low transfer equations. This is

the biggest influence. But in any case, it's going to be a little less

influential than the roll center height that I can tell you. So with

lateral movement, steeply I'm trying to keep it within the wheel track

with, let's say, but at least it's a little less

influential than the roll center height. So if I can simplify everything,

try to minimize the variation of the roll center just to simplify the issue

so that you understand your car, your belt, your suspension.

Focus mostly on vertical movement because it is the most

influential, but also try to keep an eye on lateral movement just so that

the suspension behavior is not changing as much from corner to corner

or at different speeds or as you brake and attack a corner and so on.

So this is how I would simplify based on how I design

suspensions, suspension kinematics. Yeah, that makes sense.

I'm guessing there in terms of the roll center height change as well, as you mentioned

there, trying to keep the roll center height change

or the gradient front to rear, the axis front to rear, kind of similar

that's going to be really important to make sure that the handling balance at low speed and high speed

is similar. I mean this is the simple way of

attacking this problem and I like it, but when we design race cars then we are not necessarily

looking for the simple answer. So in reality when I design a race car

I'm intentionally designing the

variation of the front roll center and the rear roll center differently

so that I get different behavior in low speed corners where I want a more

agile car with more rotation, compared to high speed where I want

a more stable car. Ultimately I think the thing that our listeners

need to keep in mind is that suspension design, irrespective is always

just a set of compromises that we're trying to make the best choices. There is no

black and white answer if this is the best geometry, it's not that simple

is it? Yeah, you're absolutely right. So it's a compromise between let's say

10 main parameters or maybe 50, you should look at almost

the parameters. It's a compromise, you have to find a trade-off

and remember what I mentioned that I don't like creating rule of thumb or any

rules for kinematics design because the car is all connected. If

you have a different tire front to rear it's going to ask you for a different

kinematics compromise or a different kinematics difference between front and rear

so there is no perfect solution however

at the same time there's good practice. We should expect the camera

variation should be in a given range. We should expect the roll center height should be in a given range

as long as you design like that the first way then

at least we are in a window that we can play. We can change the bars and adjust the balance

or in the next iteration of the car we can adjust a little bit

more and fine tune but it's all about iterations and trying to find the best

compromise keeping in mind this best practice in terms of kinematics design.

I just wanted to take a moment out of our interview with Bruno and talk about a

course that is going to be really relevant if you're enjoying our discussion on

vehicle dynamics and vehicle suspension kinematics and that

is our suspension tuning and optimization course.

This is one of the topics that we've been asked for

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springs, anti roll bars and bump stops and how these work.

You'll learn about damper basics, the purpose of the damper, how they work

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price. Let's get back to our interview now.

Let's move on from roll centre and I'll admit we probably started in the deep end

there roll centre if you haven't heard of it before and particularly

without the benefit of diagrams and we'll actually put some diagrams

in the show notes so people can research it a bit more if they want. It is

a difficult concept to get your head around but let's talk about one that I think people

will probably understand a little bit easier which is camber.

More specifically camber curves and camber gain.

And what we're talking about here is the vertical angulation of the wheels

and it's all really about again trying to optimise our

tyre contact patch on the track, make the most of that tyre and get the most grip

that we can. But of course again as the suspension goes through compression and rebound

the camber is constantly changing so can you talk to us about

first of all maybe the differences between a first and strut suspension

and a well designed double wishbone suspension in terms of how that affects the camber gain

or camber curve. Yes basically when you have the multi-link suspensions or for example

double wishbone suspensions in summary you have a lot more control

over the camber curve. So not only you can get better

camber curves in general but you have a little bit more

string them in designing this camber curve exactly the way you want.

What do I mean by camber curve is how much camber variation you have

as you compress your suspension. In any case we can also find

very good solutions in maximum suspension so it's not that

you should have only double wishbones even though race cars are typically

working with double wishbones because of the freedom and the fine tuning perspective

and opportunities that you have there. With the double wishbone

my sort of understanding of a way of explaining this is

well designed with the right camber curve we can

run less static negative camber so when the car is stationary

we don't have to run so much negative camber in order

to achieve the desired negative camber when the car is cornering hard

and the loaded tyre is compressed. Versus McPherson Strut

we don't tend to gain as much or be able to gain as much

negative camber during compression as a double wishbone suspension

so hence we need to run more static negative camber

and the downside of that is it's going to influence or reduce the grip

in a straight line and by that I mean under acceleration and braking

we've got less of the tyre contact patch on the ground. Is that a fair way of representing that?

Yes so just to finish here a last point that

what are the disadvantages of running a higher static camber? Not only you have less

grip in braking but you're stressing a lot more the inside shoulder

so for race cars that can be a big problem because you can even fail tyres

especially when we're working in endurance and so on. So we're trying to minimize

how much static camber we need so that in straight line we're not stressing the inside shoulder

as much but at the same time what matters the most for the performance is how much

you grip to getting the corners you have in the corner so you still need to have some

sort of negative camber so that you have perfect contact patch let's say when

cornering. But well let me explain all of that. If we go back

let's again we are taking a left-hand corner we transfer the load we can

all imagine that the car is rolling to the right side. But the thing is it's not

only the chassis that is rolling the tyre is also rolling together with

the chassis so if you had a tyre let's say camber 0 completely straight

once you roll it's going to go towards what we call positive camber and

positive camber is definitely not ideal for grip because the contact patch you

don't have a very well distributed contact patch you're not using all of the tyre

with you're only using the outside shoulder not only that but when you have

let's say negative camber which is the good camber you have what we call camber thrust.

So it's not only about the area of the contact patch but once the tyre is already pointing the

direction of the corner you're already gaining some grip in that direction.

In any case if what we roll we gain positive camber which is what we do not

want on the outside tyre in this case the right side we need some static

negative camber so let's say that when rolling we were losing one degree of

camber maybe we need one degree of static camber but what's the

interesting part here the camber variation is not only defined by how

much roll you get it's also defined again by your kinematics so if you change

your kinematics you can lose let's say or you can gain less positive camber when

you're rolling so now instead of gaining one degree of positive camber which is

something that we do not want if we optimize our kinematics design and we

change our camber curves now we are only going to gain half a degree of positive

camber so while in the first scenario we need the static camber of one degree

now we only need half if we go for the extreme case if you design a really bad

suspension you could be gaining up to two or three degrees of positive camber

which is terrible for the tyre you need to run a lot of static camber

and in an optimized suspension you could expect to lose half of that so you can

decrease by half the static camber that you are using so you can gain straight line

but you can also gain in cornering and you also get a more well distributed

tyre wear along your contact patch.

Okay perfect I think like I said at the start the camber side of things probably

a slightly easier concept for people to get their head around but I think there's

a lack of understanding obviously people who have been to race tracks will see

that cars have negative camber but why we need that negative camber and why some cars can

get away with less or maybe need more is something that goes a little bit deeper

so thank you for that description there.

Let's move on to another element which sort of goes hand in hand with this just

as the suspension moves through its bump and rebound travel is the tow curve

or another terminology for that would be bump steer.

Basically whether the wheels will start tracking inwards or angle inwards or outwards

as they go through bump and rebound so I mentioned I think a little earlier

most people would probably assume that a well designed suspension system

we would have zero tow change as the wheels move through their travel.

The reality might be something different is the desirable elements of tow change

that we are trying to achieve with our suspension.

It actually goes to the exact same discussion as the Rolls-Rainer.

Whenever people are designing a car for the first time I'm going to recommend that they

design for a no-bump steer meaning that as you compress up and down the alignment is not changing

because this is the simple way it's very easy for you to understand what's going on with your car.

Now when you're trying to fine tune and design a winner race car then you are starting to play

with the nuances so not necessarily we want zero bump steer when we're designing a car

we want the bump steer that it needs to have ideal balance so let's say that the previous

iteration of this car had a lot of instability under braking maybe we're going to design a bump

steer that whenever the car is braking and going up the rear axle is going toe in meaning that the

tires are pointing inward increasing the stability of the rear axle or when it's cornering you can

have the rear tire if you need more rotation when it's cornering the outside tire is going toe out

for example on the rear which helps you get more rotation on the car so it all depends on what

you want to achieve with that particular car so it's not necessarily the case that the bump steer

is bad however for 95% of the time I'll tell people design a car with minimize bump steer so that you

understand your car you understand the car behavior and you have no surprises when you're running it

at the track so it all goes back to the example that you gave when you make a suspension change

the first thing you should keep in mind even before roll centers even before camera curves

the bump steer if you have very bad bump steer particularly on the rear which is even more

influential than the front you could have terrible car performance terrible car handling just because

of that so whenever you make a suspension change ideally run it in the virtual world such as with

optimal kinematics so that you can anticipate what's going to happen and optimize your bump steer

or the least you should be doing is in your workshop design a system that you can move your

suspension up and down and measure the angle variation the toe variation to understand how

much bumps you have after a change because this could explain all the balance issues that you're

going to get at the track absolutely agree I think understanding what you've got in terms of a starting

point is really really critical just sort of coming back a step though we talked about camber and

how the camber curve will influence the amount of static negative camber that we need to run

but I think probably we've got a similar situation with tow curves as well, let's try and simplify

so generally we sort of will find that if we run a small amount of tow out on the front axle line

that tends to aid turn in into a corner and the problem with that though is that if we're running

a lot of tow out then in a straight line in particular at high speed that creates a lot of

scrub which will reduce our top speed and basically put a lot more stress on the tyre so ideally for

straight line performance we would like zero tow but of course then as we get on the brakes

compress the front suspension and begin to turn into the corner we would like to move to a little

bit of tow out, likewise at the rear of the car again in a straight line we would like zero tow

but as you've mentioned we're there with braking stability if we happen to be at zero tow and

some compliance in the suspension bushes that may move to tow out making the car very unstable

or we've got a tow curve that moves towards tow out as the rear of the car

moves into rebound and lifts up, obviously undesirable so by properly designing this

you can get a tow curve that allows you to run or allows you to run with more zero tow,

less scrub in a straight line but still get the desirable elements under braking and cornering.

That's it, yeah you're completely right. Some interesting parameters that the rear

tow is pretty straightforward as you run more rear towing you're going to get more stability

and less rotation of the car which is good when you have an unstable car. The front tow to be

honest it changes from car to car, there are some cars that will be benefited from running

tow out, some cars that will be benefited from running tow in terms of how much response they get

but yes that's the idea, bumps to your wheel influence the dynamic tow just like

we have the dynamic camber, we have the dynamic tow which in the end defines the car behavior

so yes you're right in what you stated. One thing that you mentioned that I think is particularly

important first you mentioned to highlight is the importance of bushings because it's not only

about the kinematics, it's also about the compliance because if you have if you change your bushings

you can change how much camber variation you get from compliance, you can change how much tow you

get, so it's pretty interesting to keep that in mind of going from a high stiffness to another

high stiffness, the change is going to be minimal but it's just something that you should keep in

mind in case you change from very soft bushings to very stiff bushings, most of the case you're

going to improve typically as you reduce compliance you're going to improve the kinematics but if you

go the other way around then it could be dangerous then you could start getting a lot more bumps here

than you would expect dynamically at the track. Of course if we're talking about professional

race cars or even sort of most higher end club level race cars we typically get rid of rubber

bushings and we'll move to a spherical bearing which maybe doesn't entirely eliminate compliance

but certainly gets rid of it but it's probably a big topic in and of itself but probably the

important point here to note is that it is a real thing and it is going to affect your geometry on

the track and depending on the bushing type that will also affect how much it changes.

Now another topic that I wanted to pick your brains on here and this is one I've really

struggled to find much information on its actual relevance and a lot of the information I see is

actually conflicting and this is Ackerman steering and again unfortunately very complex in terms of

explaining what Ackerman steering is, hopefully you're going to have a nice easy analogy for us

but again hopefully we can also put an image in the show notes so that people can review that

and get a better idea. But Ackerman steering, high level, what is it, how relevant is it and

what do we need to know about it? Here we go, so Ackerman is the difference of steering or

alignment between the inside tire and the outside tire so again we are going for a left we're taking

a left hand corner the inside tire would be the left side the outside tire would be the right side

so what's the difference in steering that you get? The extreme case which we call pro Ackerman

would be the inside tire steering a lot more than the outside tire and the opposite would be

anti Ackerman where we would have the outside tire meaning the right side in this case is steering

a lot more than the inside tire so first of all how do you get this difference? Again it's all

coming from kinematics depending on the angle of the links so for example or the steering

reposition it's going to influence the steering on the left side versus the steering on the right

side why is it important? Well it's easy to explain why it's important because we just explained how

crucial tow or bump steer is so if you have any variation it's going to influence a lot of the

car behavior even more than camber and the Ackerman is directly defining that so as your steer you

basically have a variable tow so you can put a dynamic tow out if you have pro Ackerman or a

dynamic tow in if you have anti Ackerman so it is very important because the tow defines the

bangle which is how much you are slipping the tires which directly defines the tire forces

all right so I think it's clear why it is so important and why it's so influential car behavior

but now which one is better pro Ackerman or anti Ackerman? Well this is the conflicting element

isn't it the million dollar question? It is it is and you shouldn't expect no difference from me

but I cannot tell you which one is better it depends on multiple parameters just show us a few

the car itself so its dimensions weights the tires that you are running there are some tires that

has for a more pro Ackerman there are some tires that has for a more anti Ackerman and also the

type of racing if you're running very low speed corners or very high speed corners they are going

to ask for different Ackerman numbers all right but now why do we want first of all why do we

want in the first place to steer differently on the inside tire and the outside tire it is basically

because the outside tire will be more loaded compared to the inside tire and a tire that is

more loaded could ask for a different slip angle compared to the tire that is less loaded

to generate peak grip. Coming back one step though something you haven't mentioned which I always

see in discussion on Ackerman is the inside tire and in your example we're turning left so that's

the left hand tire that's actually if we sort of drew a circle around a central axis or central

point and then we drew another circle for the outside of the car obviously you know depending

on our track the outside tire the radius that that's moving through is not as tight as the inside

wheel so that's sort of the argument for Ackerman that I've seen, is that a reasonable element

to discuss? Yes for sure it is connected to the discussion but it's an over simplification let's

say. In any case it's very good that you bring up this concept because what do we say perfectly

Ackerman or 100% Ackerman it is basically because we're following what you described if you take

the center of the corner and we draw a circle or connecting to the inside tire or a circle

connecting to the outside tire we see that the inside tire will steer a little bit more it needs

to steer a little bit more than the outside tire and yes there is some validity to it but it is

a simplification because we have a couple other parameters. All right so the next parameter is

what I just described tires with different loads would ask for different slip angles so let's say

that your outside tire asks for a higher slip angle it needs more slippage when it's loaded

it is asking for what for an anti Ackerman geometry because it is trying to put more it's

asking for more slip angle or more steering on the outside tire compared to the inside tire

but then you go for other tires that ask the opposite they want more slip angle for the inside

tire compared to the outside tire in that case it would ask for pro Ackerman in any case it is

very hard for us to know what our tires are asking so what I'm going to give you is some advice on

regardless of the tire what approach you should use to try and determine the best Ackerman for

your vehicle so first of all it depends on the type of racing that you're doing a rule of thumb is

the following the lower the speed the more rotation the car needs we obviously did a lot more rotation

low speed corners compared to high speed corners the more rotation you have the more pro Ackerman

you need because naturally as the car takes a corner the slip angle on the left side and right

sides are not the same because of the dynamics of the corner regardless of Ackerman regardless of

the steering they're not the same and the lower the speed the more pro Ackerman you need to have

both tires and the same slip angle which is a good bet whenever I don't know is this tire pro Ackerman

is this tire anti Ackerman I don't know let's go for the same slip angle on both sides so the same

slippage on left and right sides so in that case the lower the speed the more pro Ackerman you should

have and for example when you go to formal student competitions I don't know if you're familiar with

the steering but it's a very low speed that project that I was discussing in the beginning of the

episode it's very low speed typically even if your tire is asking for anti Ackerman typically a pro

Ackerman approach will give you more front grip and it's all about maximizing the front grip

the higher the speed then you can go towards more anti Ackerman because naturally you're not putting

so much as the pango or the dynamics of the corner are not imposing so much as the pango on the

outside tires so you can have a more anti Ackerman approach or more let's say parallel steering

which is another approach that we didn't discuss so this is number one and then another very efficient

way to determine if your car and I think you're gonna like that one to determine if your car needs

pro Ackerman or anti Ackerman you need to find a pretty big parking lot or testing area or a

proving ground where you can do a skid pad in a radius that makes sense for whatever type of racing

you do how can we simulate Ackerman remember that I said that pro Ackerman is as if you put

dynamic tow out and anti Ackerman is as if you put dynamic tow in you can simulate an Ackerman

geometry not by changing the pickup points but by simply changing the tow so you can do the same

skid pad with tow out with tow in and then it's on you or on the data analysis to understand which

one gave me more grip that's a really good tip because basically you're simulating the Ackerman

without changing anything on your suspension once you understand okay Mike it seems like if I put

more tow out meaning that I decreased the slip angle on the outside tire I'm gaining grip all

right if I'm putting tow out this is the equivalent to pro Ackerman so maybe my car needs a little

bit more pro Ackerman than I currently have so this is a very good way of testing on track what

your car is asking for. Yeah that's a great takeaway I would not have considered that because

typically at least when we're dealing with production cars actually making changes to

the Ackerman is not a simple task so it's not something that you're going to be able to go on

make five changes with at the track and kind of get a sense so having that ability to see

what the car actually wants and then allowing you to then make the hardware modifications to

actually achieve that definitely going to be a big time saver. And I have one last suggestion

in terms of Ackerman for those designing the car especially the upright you can design multiple

pickup points as long as you use a kinematics simulation software where you have pro Ackerman

and MTR so whenever someone asks me what Ackerman should I use especially if it's a race car

manufacturer or a formal student team I tell them design both and let's test it at the track because

there as I said it's such a complicated subject but I'm not even going to take the time to explain

that most of the time it's a lot more efficient if you tested that the track compared to just

theorizing what what goes on behind all this theory. Yeah yeah absolutely another thing I

just wanted to come back to as a term that you have used quite a bit just there and just for

the sake of clarity for those who who aren't sort of following along slip angle in relation to the

tyre what does that term mean? So whatever you are taking a corner your tyre is not sliding

the same direction as it is pointing so for example the front tyre is steering at 10 degrees the

tyre is actually not going that direction it's going at a five degree different direction this

five degrees is exactly the slip angle so it's basically the sliding of the tyre so it's the

sliding angle of the tyre and tyre forces are all about this sliding angle same on the rear

even though it's pointing straight the rear tyre is not going in that exact direction it's going

at a five degree angle or a 10 degree angle which is exactly the sliding energy sorry the

slip angle and this is the angle is what is generating tyre forces so that's why we're

trying to find what's the ideal slip angle to maximize tyre forces that ideal slip angle could

be different left and right sides that's why we play with the Ackerman geometry exactly to put

each of the separate tyres at their ideal slip angle. Okay and that ideal slip angle as you've

also mentioned just to reiterate is going to vary from one brand of tyre or compound of tyre to

another as well. Right and just to give a very concrete example whenever you have a more reactive

tyre it is probably because not only because it has more grip but also probably because this

the ideal slip angle is lower if we need a smaller slip angle the tyre will be a lot more reactive

because you steer just a little bit it is already close to the ideal slip angle it's already generating

most of its grip or it's already maximizing the grip so when you go from a typically passenger car

tyre to a sports tyre your slip angle just to give an idea your ideal slip angle is coming from

10 to 15 degrees for a passenger car tyre down to 5 to 7 degrees for a sports tyre that's why

it's a lot more responsive. You know that makes perfect sense. Alright I think we could go on

forever on this topic there is two more elements I do want to discuss in terms of the suspension

and that's the terminology anti-diving, anti-squat. What do these mean in terms of geometry and again

can you give us any guidance or any rules of thumb again it's one of those elements that

seems to there's quite a lot of conflicting information around. Yes so actually it's going

to be easy to explain because we already discussed row centers and they are the equivalent of row

centers why row centers are defining the load transfer electrically so lateral load transfer

the anti-dive and anti-squat are defining the geometric weight transfer or the load transfer

longitudinally. So let's go back to our example remember that we said that we had a cg of 400

millimeters why we had a row center of 200 millimeters this is a split of 50 percent guess

what this is the equivalent of a 50 percent anti-dive in this case of the row center when we

were taking a corner we knew that 50 percent was going through the springs and the car was rolling

because of that while 50 percent was going through the length and the car was not rolling because

of that component that means not on the suspension. Anti-diving and anti-squat are exactly the same

so when you tell me I have 50 percent of anti-dive this means that when you're breaking and transferring

load to the front axle 50 percent is going through the springs causing the car to pitch more because

you're compressing the springs while the other 50 percent is geometric and is going through the lengths

and you are not pitching because of that so what's the advantage of running high anti-dive the car

is pitching a lot less you can run the car lower because it's not going to touch the ground you have

quicker load transfer so everything is more stable the platform is more stable.

What's the disadvantage well first of all there is a lot more load going through the links so if

you're getting a lot of suspension failures you should ask if it's because either you have too

high of an anti-dive or you have not designed your components appropriately for those loads for

that specific anti-dives so this is the disadvantage you have so much load transfer through the links

that you can start having suspension failures and the last thing is that for beginner drivers

if you have a little bit more suspension movement it's better because they have more time to feel

the car when you go through race cars then you have a lot higher anti-dives because the drivers

are so good that they don't need any time to think they can have this instant load transfer through

the links instead of a slow load transfer through the springs but that's why you would run higher

or lower anti-dives and the equivalent would be anti-squat when you are back on the throttle

instead of braking. Okay so I mean just like everything no real black and white here just

different shades of grey but depending there on the driver I mean I'm guessing in terms of the

mechanical strength of the suspension components that's relatively straightforward I mean they

can always of course be designed to cope with more load the parts just end up larger and therefore

heavier and obviously waits the enemy of performance when it comes to race cars but

sounds like there are a lot of it really is going to come down more to the driver's preference

and driver's skill level is that fair? Yes not only driving but also the goal of your car if it's

an aero car you could afford running higher you could want to run higher values so that you

don't have as much platform variation which shifts the belt force from the rear axle to the front

axle so yeah there are a couple of different parameters it all depends how responsive or

you want your current how much platform control in any case I don't like giving a final number

because there is no final number I can tell you what's typical for a race car for a race car

typical number is between 30% all the way up to 100% that's the typical number for a race car

for anti-dives for anti-squat a little bit lower typically from 20 to 60% is a typical range for

race car. Okay so would A building enough adjustability into the suspension to move

the geometry like that be beneficial and then B those ranges that you've just said

is it safe to assume that starting somewhere in the middle of those ranges for anti-dive and

anti-squat would be a fair place to start our testing and then try varying it and seeing how

the performance changes? That's what I would do yeah I would be happy with that that's what I do

when I design a race car I start there and then I understand what the car needs for further

changes. Alright let's park that and move on I like I say we could probably talk for another hour

on it but I think we've covered like some of those key concepts there and hopefully that's

reinforced their importance to our listeners. The next piece of software I want to talk about

is Optimum LAP and you've really kind of given us a brief sort of understanding of what that is

you can model the car and get a sense of making a change to this parameter is going to give us

this result in terms of lap time. Now obviously the race car is an incredibly complex thing

and you've said that you've simplified it down to the key inputs that you've found

necessary and again this has come back to this garbage and garbage element and breaking it down

so it's easier for the user to actually come up with the right numbers to put in to get

sensible results so could you give us an idea of what data is required to use Optimum LAP?

Yeah so basically we identify the primary contributors to performance and it's the

these are the only ones that you have to put in the software so as you know the weight of the car

so the mass then after that we have tire grip which is extremely important then we have

downforce and drag then we have engine curves and then we have gearbox and gear ratios that's

pretty much all you need to run simulations in Optimum LAP and why is it so effective because

these are the primary contributors to performance and to lap time everything else is just fine

tuning how you can exploit the tire grip to try and increase this tire grip a little bit more

or try to gain a little bit more downforce but all of those are secondary parameters

besides that we need to build the track right because it's one thing having the car and then

the second thing is having the track so you have basically two options in Optimum LAP either you

build it manually you can say okay first I have a corner with these radios and so on which is a

pretty tedious work but the good thing is on our website you can upload real data of very basic

sensors you only need to be lateral acceleration and these can start time that's pretty much it

and you can convert this real data to a track map then you can import this track map into the

software now you have the car very simple car very simple track and you can run simulations

to understand what's the car performance great I mean that was one of the questions I was going

to get to is how on earth do we build track maps because that in and of itself is a pretty big job

if you want to be accurate okay so coming back to those parameters some of them I'm sort of thinking

pretty easy I mean the weight of the car not very difficult to get that likewise I mean anyone

who's had their car tuned the torque and power curves of the engine pretty straightforward

gear ratios again pretty straightforward. Aero that's a little bit tricky if you're buying aero

components from a higher level manufacturer they're probably going to be able to give you

data on downforce versus drag a little bit difficult to get maybe on some of the more

let's say homemade components but the key one that I'm sort of wondering about is tire models

and you've talked about the tire performance and tire grip and how on earth are we supposed

to come up with this data that sounds like it's complex. It is not actually it's just

simply the other ones at least in Optimal Lab at least in Optimal Lab so we don't require a complete

tire model we only require tire grip and there are two ways that you can identify the tire grip

which would be basically the peak grip of the tire. Number one you can take a typical number for

this type of racing or for this type of tires so we know what number we should expect for a racing

lake for a passenger car or a sports tire. The second way which is what I do and what I

recommended people doing is the following many cars you are logging the lateral accelerations

then the longitudinal accelerations right how do you get to those accelerations they are basically

because of the grip of the tire therefore what I do is the following I run the first simulation

in Optimal Tire I extract the results upon them let's say in Excel I get my real data I also look

at it and let's say that my peak deceleration under braking was 1.3g on the real data but in

Optimal Lab I'm getting 1.5 what do I do I tune it down a little bit the longitudinal coefficient

of friction until I can get to 1.3 matching the real data then I look at the apex at the apex

when cornering I'm taking 1.1g but in the simulation I'm reaching only 0.9g so I can increase a

little bit the factor until I match the data and once you have it matched then all of the work

after that I have to say it's pretty accurate so if you do this initial validation of getting

down first right of getting tire coefficients right anything that you do after that for the

primary numbers such as mass engine curves gear ratios and so on will be pretty accurate will

be more or less what you see if you do that at the track so it is a really nice way of identifying

okay if I increase my is it better if I invest money in decreasing my car weight by 50 kilos or

should I increase my power by 5% you can actually simulate that in Optimal Lab with minimum inputs

and you're going to get a very accurate answer okay yeah that breaks it down into something

that sounds relatively manageable and again you don't have to be a rocket scientist in

order to be able to actually generate the inputs and get useful data I mean the obvious question

is here how accurately does this validate to real world performance when these changes have

been made in the cars taken to the track very good like maybe if it's just a weight change

or something like that I think gas and accuracy of 1% it's really straightforward yes the only thing

is that in real life if you change the weight but also the weight distribution this will change

car balance and then it's going to be a lot more than 1% so if you in real life if you're able to

simplify and keep the same weight distribution only removing mass or if you can increase the

tire grip by 1% the results would be pretty accurate let's say between 0 to 5% accuracy is

what I would typically expect as long as you can really model what what's going on because let's say

that you change you think that you change your engine power by 25% but actually your curve

changes lightly if you as you said garbage in garbage out so as long as you can really model

what happened on the real car the accuracy will be pretty high if you do that first phase of

validation of the arrow parameters and also the tire parameters yeah okay right let's move on to

optimum tire so again you've given us a high level understanding of that and this is one of those

areas that I'll admit I have not dived deep into and every professional race engineer that I talked

to just it always comes back to a conversation around how complex the tire is and how important

understanding the tire is to getting the performance unlocked from the car and I mean obviously

ultimately no matter how much power we've got how much downforce we've got how much money's been

poured into developing the car ultimately it's those four tire contact patches that really

make or break that ultimate performance of the car around a racetrack so give us an understanding

of what data you're generating from a tire and even sort of how that's achieved so there are two

ways of understanding the tire and at the professional level we try to use both the first

one is testing the tire in a lab so as I mentioned we have a machine that is called a flat track

machine which is a huge machine where you mount your tire as if it was a car there is a rolling

floor and then you can steer you can add or remove load you can change the pressure you can

change the camber and you can measure what's going on so you try to quantify the tire in

all different possible conditions and combinations of load camber slip angle and so on and you measure

and you log the forces and moments being generated then you take all of this data you put inside

option tire and option tire will help you process this data once you process and make sense of the

tire all right so the tire ideal grip is in this temperature window which is a test that we can

do in this type of flat track the ideal slip angle is five degrees the ideal pressure is 1.8 bar

once you've done all of that you can then create a model on top of that so you don't depend on the

raw data anymore you have a mathematical model that you can put in any z-co dynamics simulation

software after that you can run simulations to understand right first I had only my tire now

I have the whole vehicle what can I do to the vehicle to optimize the tire performance okay so

this is from the aspect of testing the tire in a lab and then running simulations the more practical

approach which is not replaced by the lab tire at all is to optimize the tire and the track and

this is where the work of a performance engineer such as myself or even a tire performance engineer

which is another role that I play this is what we are doing at the track we are trying to analyze

dozens of different sources of information to understand how our tire operates and how we can

optimize it meaning what's the ideal temperature that we we are looking at that we we should try to

choose what is the ideal pressure or the ideal pressure range what is the ideal dynamic camber

what's the ideal even acrimon told that we will optimize tire usage flip angles tire temperatures

all of the same time and on top of that when especially when you're running enduro races you

need to look at performance degradation so tire wear and tire thermal degradation so we are measuring

the tire wear in all the different measurement holes to understand wear distribution and understand

okay we have a very asymmetric wear meaning that we're not using all of the tread all of the tire

performance what can we change on the car setup to optimize and make the tire more consistent with

a more distributed tire wear on the contact patch so these are the two different approaches that

you have in order to better understand your tires lab simulation and then track analysis

all right so the lab simulation obviously for probably 99.9% of our listeners maybe even 100%

of our listeners is probably not practical or realistic but some of the concepts that you

talked about at the track these absolutely are can you give us a little bit more insight there

like what input what data are you relying on here to help optimize these elements I mean

obviously tire pressure is easy to monitor and check are you looking at tire pyrometer readings

when the car comes back into the pits are you looking at live infrared tire temperature data

on the tread across the tread width while the car's on the track sort of what that's doing

dynamically or is it all of the above so let me give you a few examples of what a tire performance

engineer is doing at the track because it's going to give you very applicable um traits or methods

for you to optimize the tire usage of your current track so first of all yes we're discussing what we

can track but even before that we need to define what we want to achieve with the tire so what do

we want to achieve with the tire we want to maximize grip and we want to have consistent grip

because it makes no sense for it to have ideal grip in one in one lap then you overheat your tires

and you have no grip whatsoever so we're trying to optimize grip and have a consistent tire how can

we quantify that there are a few different ways the first and most practical way is looking at

driver feedback so you as a driver you should have a very good understanding of tire grip

tire performance car balance it's not only about finding the grip but it's about finding a balanced

grip between front axle and rear axle so us as tire performance engineers we're speaking a lot with

the driver taking notes of what happened and tracking the conditions because if the driver is giving me

feedback when the air and track temperature are 10 degrees see it's very different from when the

track is at 50 degrees c and then the air is at 30 degrees c so I keep track of driver feedback and

what conditions that feedback was valid so the driver is telling me okay the tire took me a

long time to warm up I had only very good grip after three laps now I'm thinking okay what can I

change in the setup or in the driving style to make that warm up quicker then the driver tells me

the grip was not that good when we stabilized okay maybe the grip that I'm thinking maybe the

tire is not at the ideal operating window is it too low is it too high how do I go up and down

and then lastly the driver is going to tell me but look actually the tire grip on the front

was pretty good but on the rear it was not so in that specific outing I was having a lot of

oversteer now I can think okay what can I change in the vehicle balance to fix that all right so

we defined first what we wanted then how we get this information from the driver there is something

else we can do we can look at the data and try to quantify with the data under sear over sear

we know that by looking at the steering profile we can very well quantify or at least see under

sear and over steer after that we need to decide okay what do we do with all that information

what tire parameters can I keep track to understand if the tire was too cold or too hot then it all

goes back to the good examples that you gave so tire pressure we should be measuring the cold

pressure when we leave the pits and the hot pressure because there is a whole art behind

defining cold pressures to achieve the ideal hot pressure that you want how do you know what's the

ideal pressure that you want well there are many factors it's a lot about experience or running

different hot targets or hot pressures and understanding which one gives you the ideal the

best grip but it's also a lot about driver feedback because if you run very low pressures your tires

become unresponsive if they're lazy why because when you steer they first need to deflect naturally

because now they are very soft before the grip and generate grip for you so typically what I do

with race cars I keep lowering the pressure lowering the pressure until the start the tire

starts feeling lazy and responsive and they don't give me the confidence or the support when I'm

rolling that I want and then I can find okay what's too low and then if I keep increasing from there

it's I'm going to start losing grip and then I can define ideal pressure and we keep track of that

with the pressure gauge now speaking about temperature what can we do to track that yes one

of them is the the parameter so actually there is the ideal measurement and the non-ideal measurement

the non-ideal measurement would be with a laser gun or with an infrared gun because you're only

reading there's only measuring the surface yes you're only reading the highest surface or the

the most outside surface of the tire which two things number one is not really what's going on

at the track because there is a lot of temperature inside of the rubber that is extremely important

number two when you finish your lap and you come back to the pits it takes you a few seconds until

you make the the measurement and the temperature is going down more interesting if you go to a

different track with a different pit lane length or first thing at the beginning of the pit lane

or at the end of the pit lane this is going to influence your reading we see that it's not

representative of what's going on at the track the best way one is use a temperature probe

where you have the needle and you can put it the needle at a 45 degree angle you go a few millimeters

inside the tire that one is very representative it is a lot closer to the temperatures that the

tire was seeing around the lap and it doesn't cool down as quickly as the surface temperature

all right so now we know how to track temperature how do we determine what's the ideal temperature

again you have to run in a cold conditions then in warm conditions track everything

take notes take feedbacks look at the data and then try to connect everything to determine all

right so i had maximum grip when my temperature measurements were in this range so whenever

in this other event i need to either change my setup to increase or lower the temperature

you gave a very good example for example the toe it's not the only one but it's a good example

or how can i drive differently to warm the tires more i need to be more aggressive i need to

over drive a little more or actually i need to reduce the tire temperature so i need to be a

little bit more careful a little bit less aggressive over drive a little less and a strategy that we

using professional motorsports is whenever we have to lower the temperature or decrease the wear

there are specific corners where you take them slightly slower so that you do not overheat the

tire such as high speed corners that are putting a lot more sliding energy or energy in the tire

so that's how i would say that first we define what we want to choose then how do we track that

and then how we can optimize pressure and temperature for a decent situation

okay this again just like everything else we've talked about is probably a podcast episode

on its own but i just want to dive a little bit deeper into it so you mentioned essentially the

laser measurement in the pits and if not really going to give us much feedback because it's just

measuring the outer surface which is going to lose temperature very quickly as you're rolling

down pit lane. You mentioned the tire pyrometer that's going to measure the tread below the surface

so get a much more representative reading. You didn't mention the infrared tire temperature

measurement actually on the car you know measuring the temperature in real time in the

data analysis or data logging as the car's cornering. How useful is that, i mean as i see it

on face value, that would be the optimal because you're actually seeing what the tire tread is doing

in terms of temperature and temperature spread across it while the car is loaded up in the corner

which is what we want to know. Yes absolutely let's say that we go for this a little more expensive

solution. It is the best that you can get the only thing i have to warn you is that it's not

easy to look at the data but i can give you very good insights here of how to interpret this data

because a couple of years ago i wasn't struggling myself to come up with useful metrics from the

sensor because you get so much data so many channels in different sections of the tire

that you need to create a very systematic way in order to process the data. So in very high

level theories then we can use temperature sensors actually many of them it's banned you

cannot at least you can only do in private testing however we developed very good methodology to do

that. So what are the key metrics that i would try to extract from this data? This data is going

to be changing it's going to be all over the place each of the corners is going to have different

temperatures so i try to simplify that into a couple very useful metrics. One of them would be

the following as i mentioned with temperature sensors reading the temperature around the lap

first thing if it's on the front axle and the sensor is not following the tire as it steers

you have to be very careful with the results right on the rear it's a little bit more straightforward

though it is possible for it to create a mount that it rotates with the upright and then you

keep reading the inside shoulder the center and the outside shoulder. Typically i like to have at

least three readings as i said inside middle outside but many times we have many more my

suggestions simplify it if you have five only pick the outside middle and inside this is more than

enough for us to analyze. Let's go back to the metrics so the metrics that i try to look at are

the following average temp i don't look at each channel in all different conditions i create

metrics which are average channel of the three channels when cornering because a lot of people

create this metric around the lap but around the lap you have straight line where let's say it's a rear

wheel drive car the front tire temperature does not matter so let's think about lateral grip create

this metric only looking well only look at it for example when you are at the apex this is a very

good way of simplifying it so i create one metric which is average tire temperature when cornering

you can filter it only when you have high lateral accelerations you create this metric and the second

metric which i believe is very important is the distribution so inside shoulder minus outside

shoulder possibly when cornering as well why because it gives you a very good idea of what

your dynamic chamber is doing to your tire if you have your inside shoulder very very very warm

even when cornering converge to the outside shoulder maybe you are running too much camber

you are too much on the inside shoulder your contact patches focusing too much on the inside

shoulder when you're cornering while when you see a smaller gap of inside temperature and outside

temperature when cornering this means that you are making better use of your contact patch meaning

that you probably have a proper camber just be careful let's not oversimplify because in straight

line you are driving on top of your inside shoulder so it will naturally have a higher

number even when you corner so just be careful with how much you want to really have the same

temperature inside shoulder or outside shoulder but with experience you start learning a little bit

more of what is a good distribution for your car or when you have good grip what is a typical

distribution that you see or what is then a typical average temperature that you see when

cornering so this would be the best strategy to analyse tire temperature.

Yeah I've found that the on board infrared tire temperature data is not maybe as straightforward

to analyse which you've just given us a nice reason for or indication of compared to what I

thought it would be prior to fitting these sensors and I absolutely agree with you that

particularly if you're not a professional engineer less is more when it comes to those

data points we've got is erasing sensors on one of our cars which will run up to 16 channels and

I mean it's just generating more noise that you have to get through so I actually did simplify

that back to just three points across the tire but again on face value you'd think alright well

this is going to be the perfect data I can see exactly what's happening to the tire tread temperature

through the corner but the reality of course and I mean it makes sense really when you think

about it just like you said you're coming into the corner, the car has negative camber so it's

predominantly running on the inside edge of the tires up to the braking zone so obviously the

inside of the tire is going to start at a higher temperature as you initiate the corner and turn

in and move through the corner then as the car rolls onto the outside of the middle and the

outside edge of the tire obviously those will start to build temperature.

So then the next question for me was alright well at what point through this corner now

do I look at this data to get a sense of is my camber and my tire pressure correct

because these are constantly moving targets so thank you for your little tips there,

I am absolutely going to steal those and apply them to my own car.

One other element I just wanted to come back to as well because obviously as you mentioned the

infrared tire temperature monitoring, it's an expensive step up, tire pyros that you'll use

in the pits, these are much more accessible and relatively cheap I think, anyone even at club

level should probably be considering purchasing one but much the same even when we're measuring

the temperature below the tread, this is going to equalise quite quickly particularly if the

last corner before pit lane entrance is quite a long way down a straight and then maybe as

you mentioned earlier, maybe you're down the end of pit lane so there's quite a long period of time

with the car rolling mainly on the inside edge before you can take those tire temperature

readings so I think again most people who haven't done this before would think alright well

we're looking for the exact same tire temperature number across the tread, inside edge, middle

and outside edge when we're using our pyrometer. I haven't found that to be the case and generally

I'm guessing here there isn't a black and white number like everything we've talked about

but I've sort of tried to start with maybe achieving a 10 to 15 degree spread across the tire

with the inside hottest, the outside coldest by that margin and then ideally the centre

right in between those. Does that make sense in your experience or am I off the mark there?

No, it does make sense so as I was mentioning this is such a complicated subject that we need to

create a few rules to work with otherwise we're stuck in what we're not doing anything. On the

professional motorsports world this is the range that we're typically expecting a 10 degree split

between inside shoulder and outside shoulder. If we're slightly outside that it doesn't mean

that we necessarily have an issue, if we're at 30 degrees higher on the inside shoulder than

outside shoulder, yes then we should be worried. We're probably running way too much camber so

the range you gave is pretty good and I would go with that as a starting point until we better

understand our tires. What I've also said as well is maybe start by baselining the car and

getting yourself within that range but like let's say for example it's 15 degrees, well maybe make

a change and see what the performance difference is. If it's a 10 degree spread maybe go the other

way, what's it like with a 20 degree spread? I'm basically just throwing numbers out there but

again I mean just basically mentioning there is no black and white rule of thumb that we have to

stick to. It's a case of getting a baseline and then saying is it better with less, is it better

with more? Actually make some adjustments and try these things. Good advice there?

Yes but at the same time I'm gonna go a little bit against what I do in professional motorsports

when we're just at the track trying to optimize our own car. We should understand that there is

only so much we can optimize with the information that we have so it is important to know okay we

should not completely disregard tires because they are the most important parameter but there's only

so much we can do with the information available so if I get within this range maybe I'm not gonna

overthink it because if I change the camber to change this temperature spread I'm not only

changing the temperature I'm changing the whole behavior of the car because of the new camber

so I'm changing multiple parameters at the same time it's a little bit hard to identify what's

really coming from the temperature change or the temperature split change or what's coming

from the camber so we just need to understand where do we stop where do we focus on the driving

where do we focus on the suspension on the arrow and so and it tells us a lot about the level of

racing to understand and to what point you you try to optimize it but in professional motorsports

we're doing exactly what you're saying we are tracking all of the runs and trying to find patterns

between different temperature spreads let's say. One last thing I don't want to do tires to death

here but one last thing and this is just for my own personal knowledge here. We're often now seeing

a professional level tire pressure monitoring systems incorporate infrared tire temperature

on the inside of the tire looking at the carcass temperature and again we run the Izzy racing

sensors on our own car like their external ones you can have up to 16 points here. I'm wondering

this isn't a parameter I have put a lot of weight into so far but I'm just wondering what you can

tell us about the relevance of the carcass temperature internally maybe what we can take

from that what we can use from that and how that correlates to tread temperature. Yeah so actually

I'm very happy whenever I work with a race car with this type of sensor so it's getting more and

more common first of all the series allowing for that but number two it's a pretty expensive sensor

so let's take a little bit of time until the team has enough sensors that match the number of

rims that they have in any case it is a very useful sensor for professional motorsports

because of a couple of different reasons it is a very robust reading contrary to the surface

temperature when we are reading the inside carcass temperature it's changing a lot more slowly

so it gives a very good indication case the tire overall gaining more or less temperature with the

sensor is this driving abusing more or less the tire when we run lower pressures and the tire has

a lot more deflection is it increasing a lot the carcass temperature or not so it's a very good way

of comparing the overall tire temperature and the changes that's made to the car but how do we use

the number itself we use it a few different ways particularly in endurance racing let's say that

we go to 24 hours of lemma in that case the inside shoulder temperature is a very important parameter

because if this temperature is above a threshold that we define this means that we're stressing

too much the inside shoulder we're putting too much energy on that inside shoulder not only that

you know that as the materials gets warmer they also get softer and it's more likely that they're

gonna rupture at some point so we use these sensors to understand how much we're stressing the tire

and how likely we are to get a tire failure over a long race so this is one of the bank

runners that we use for that sensor the second one is just because it gives a good idea of also

what the surface is doing many series we cannot run outside surface temperatures but we can run

inside let me give you an example if your carcass temperature is at 40 degrees you should not expect

that your surface is overheating well for two reasons if it was overheating in the first place

your carcass would be very warm as well and the second thing if you have a cold carcass it's gonna

drain a lot of this temperature from the surface so if you go on a long corner it's hard for you

to overheat because a lot of this temperature is still going to the carcass because the carcass is

cold now on the other hand if this carcass temperature is already at 120 degrees even if you

approach the corner with a very cold surface because it cooled down with the outside air as soon

as you attack the corner and any temperature that you gain it's gonna remain on the surface because

the inside okay this is not the right physical term but the inside tires are already saturated

of temperature so you cannot conduct this temperature from the surface to the carcass

so these are some of the ways that we're using to understand if we're overheating the tires or not

even if we don't have the outside tire temperatures and before we move on from tire temperature the

only thing that I would add which I think could be pretty good to our audience on our youtube channel

I recently published a 25 minutes video explaining about everything how tire temperature

is affecting vehicle behavior and vehicle balance so you understand how the temperature

build up will give you an understeer car or an oversteering car and I think it's a pretty useful

video. Okay great well again we'll try and incorporate a link to that particular video

obviously through this whole conversation which is now getting on towards two hours

we're dealing with some very complex topics and we have tried to consolidate them down into

white sized segments so for every single thing that we've talked about we could have probably

gone on for an hour or so on each of those topics so hopefully our audience can appreciate that

and on that note I think it's probably time that we did move towards wrapping this conversation

up so we don't go for another two hours. So Bruno first of the three questions we ask all of our

guests what's next in the future for you personally and also Optimum G? Right so for Optimum G we

actually have big plans we we hope to expand the company to tackle many different challenges that we

see in the market especially connecting deco dynamics with all the different systems of the car

and a lot of the challenges that our customers face in these areas so we really want to

continue to connect different tools connect different solutions and empower our customers to

better deco dynamics decisions and improve their decos that's our mission we're going to keep

expanding on that front we want to give more advanced deco dynamics or create more advanced

deco dynamics tools create more advanced data analysis tools and we are headed in that direction

besides that for me personally I will keep growing as the head of consulting so I want

to tackle more and more projects coordinate all of them and make sure we're building so

what I like to do is whatever we have a very challenging project at Optimum G I'm the one

tackling it at first but then I'm bringing my team with me so that the next time they can tackle that

so I want to keep pushing more and more in my consulting team towards more challenging projects.

Sounds great and obviously your day to day sounds like it's always pretty exciting never the same

thing so yeah sounds like a position you'd probably never get bored with which obviously is ideal.

Next question for you Bruno is there any advice you'd give to a younger version of yourself

or maybe one of our listeners to help reach where you've got to in your career today

faster or potentially maybe avoid some pitfalls that you've seen along the way.

Yes I have a couple of important insights to share the first one is you've got to work a lot

I know this sounds obvious but there are so many people that want to become race or performance

engineers so we really have to work a lot you have to work more than all these other guys

let's say and because of that it needs to be something you love because it's one thing enjoying

cars and being a car guy and it is something else enjoying being a performance engineer or race

engineer it is a lot of stress work and there are a lot of pressure you travel a lot you don't sleep

that much so you need to be passionate about it so that you can get there. Second and possibly one

of the most important piece of advice is that if you're a student go for engineering in a school

that has Formula SAE or Formula Student project it makes a huge difference because let's say that you

are in school for five years you're going to get five years of experience working on race cars even

before you go and try to find a job so that's a huge strength for those who do Formula Student.

Besides that I would also add that you should study a lot at least for me personally this is

one of my strengths when I go to the race track I have the vehicle dynamics background to understand

and solve complex problems and whenever you're studying try to apply that as you studied it

so let's say that you're studying tire performance find a project where you can apply that being

in creating a spreadsheet to track all of the parameters that we mentioned being to go into

the track with someone to help them with our performance try to find a way to apply that

so that you can really absorb that knowledge and you can make sense of it and the last thing

that I would mention if I can add is I also recommend that you grow as a person so I'm always

trying to study things like self-development psychology how to work as a team how to work

under pressure how to be more efficient because this plays a huge role in racing because you're

always working as a team and actually this is another strength that you can have you should

work well if you're able to handle stressful situations without exploding or if you can still

treat people nicely and find a logical solution it's going to be a huge advantage in your career

so these are the insights that I would give to someone wanting to go to this direction of racing

performance engineering. Those are some amazing takeaways I've said it before and we've already

mentioned the formula student slash formula SAE element and how important that has been in so many

of our guests so as I said at the start very jealous that you had that opportunity that

unfortunately here in New Zealand at my university I didn't, I'd jump on that in an instant if I

could have had my time again. The other element there just the self-development I think that's

something that hasn't come up before but it's really really important so I appreciate that you

did bring that up. As you mentioned working in a race team is a stressful environment,

you could be the best race engineer in the world but if you do not work well under stress or if

you just cannot work in jail with the rest of the team you're probably not going to end up having

a long and great career in that industry so yeah it's a people sport so being able to integrate

with the rest of the team and work well with them is just as important as you'd be able to do your

job at a high level I think. Alright last question for today, Bruno, if people want to follow

and see what you're up to, how are they best to do so? Websites, social media accounts, what have

you got for us? Yeah so in terms of OptimumG I'll say that our website will give you a very good

idea of what our work is about. More than that we have our YouTube channel where we publish content

in vehicle dynamics, applied vehicle dynamics, being tires, being kinematics, kinematics design,

so a lot of what we covered here we have specific videos on those topics so it's OptimumG on YouTube

and also our LinkedIn it's a pretty good page where we try to keep you updated with everything

that goes on in the company. In terms of personal I use a lot of Instagram to share my work so I

share a lot of the racetracks that I'm at around the world, the consulting projects, how I organize

my day, how I plan my week and everything else behind my work I try to share there. Besides that

I also have in my bio a lot of suggestions for resources to study vehicle dynamics,

data analysis, performance engineering and guess what also self-development productivity,

leadership and communication and my Instagram is Bruno.finkle so you're gonna get a lot of

value from that as well so that's pretty much it. Amazing yeah all right well as usual we'll put

links to all of those accounts in the show notes to make it very easy for everyone to find.

Look Bruno it's been an amazing chat, it has gone long but it's also gone deep and I appreciate

your time there. I've certainly learned a lot during this chat and hopefully our listeners

have too so again thank you very much for your time today. Thank you, thank you, I had a lot of fun

and I really appreciate the opportunity to be here chatting with you today. I hope you've

enjoyed this episode of Tundin and don't forget by using the code podcast500 at checkout podcast

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to our members only webinars and our community forum. That concludes our interview and before

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Revisited: Want to Get Your Car Handling Better Than Ever Before? Listen to This.

About this episode

Honda Crx

tyre contact patch

suspension kinematics

roll centre

Ackerman steering

anti-dive

anti-squat

Formula Student

vehicle dynamics

Optimum G

Formula SAE

performance engineering

GT World Challenge Europe

DTM

Formula E

tire testing

OEM

Volkswagen Rabbit

suspension stiffness

Optimum Kinematics

tire models

downforce

engine power

torque curves

gear ratios

tire grip

lap time

Hollinger gearbox

K20 engine

naturally aspirated

chromoly subframe

tire performance

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