A swingarm is the main rear arm that holds the back wheel and lets it move when you hit bumps. If the swingarm design is wrong or wears out, the bike can feel unstable or handle poorly.
It means the bike’s steering setup doesn’t change as the suspension goes up and down. Designers want the handling to feel the same over bumps instead of getting weird mid-corner.
Wheelbase is the distance between the front and rear wheels. They’re imagining a bike where that distance stays the same even as the suspension moves, so handling wouldn’t shift.
A dyno cell is a controlled testing room or enclosure where a motorcycle (or engine) is run on dynamometers. It’s used to measure performance and behavior under repeatable conditions.
A rigid frame means the bike doesn’t have rear suspension travel. So when you hit bumps, the rear doesn’t absorb them the way a suspended rear wheel would.
Throttle just means how much you’re asking the engine for power. Turning it up or down can change forces through the chain and rear suspension, especially on older or flexy setups.
Frame flexing means the bike’s frame is bending a little when you ride. If it flexes too much, the handling can feel weird because the suspension and wheel alignment aren’t staying consistent.
Term
section tire
A section tire is basically a tire with a particular width and sidewall shape. The tire can flex and absorb bumps, so it can act like a suspension component by itself.
Term
100 psi
“100 psi” is how hard the tire is inflated. Higher pressure makes the tire stiffer, while lower pressure lets it flex more and smooth out bumps.
Goodyear is a tire company. The speaker is saying that when Goodyear was active in road racing, tire designs like taller sidewalls were being explored for stability.
Concept
two stroke era
“Two stroke era” means a time when many race bikes used two-stroke engines. That engine style changes how the bike delivers power, which can affect how the rest of the bike needs to be set up.
Dunlop is a tire company. The speaker says Dunlop also made tall sidewall tires, aiming to make the bike more stable by letting the tire flex in a controlled way.
Term
lateral flexibility
Lateral flexibility means the tire can flex sideways a bit when forces act on it. The idea is that this sideways movement can help the bike stay stable and absorb some of the motion.
Vincent refers to the motorcycle builder Phil Vincent. The speaker is talking about a rear suspension design he created, meant to keep the rear wheel from wobbling side-to-side.
If the rear tire tilts side-to-side, the tire’s grip angle changes. That can make the bike handle differently because the contact patch isn’t staying consistent.
Rear suspension is what lets the back wheel move up and down. It helps the tire stay in contact with the road and makes the ride less jarring.
Concept
TT
“TT” is short for the Isle of Man TT, a well-known motorcycle race. The hosts mention it because racing success there helped push rear suspension into mainstream motorcycle design.
Sliding pillar is an old-school way to add rear suspension. Instead of a modern shock and linkage, the axle moves using sliding supports attached to the frame.
A girder fork is an older style of front suspension that uses a strong beam structure. It affects how the bike steers and how the front end reacts to bumps.
A swingarm is the rear arm that holds the back wheel and pivots as the suspension moves. It helps the bike keep better contact with the road when the surface is uneven.
A sprung hub means the wheel hub has springs built in to soften bumps. It’s a different suspension approach than a swingarm, and it can feel different on the road.
Term
rigidly connecting the steering head to the axle
This is about how the front of the bike is mounted. If parts are too rigidly connected, the bike can’t move and flex the way it needs to, which changes how it feels when turning or hitting bumps.
Rear steering is when the back wheel subtly changes direction because of how the suspension moves. It can happen during braking, acceleration, or when you hit bumps while turning.
A shock mount is where the shock bolts to the bike. If you move that mounting point, the suspension “feels” different—how easily it compresses and how it responds over bumps changes.
Motion ratio is a way of describing how much the wheel moves versus how much the suspension moves. Change the geometry, and the bike will feel softer or firmer for the same bump.
A parallel twin is a motorcycle engine with two cylinders next to each other. It’s a popular design because it’s relatively simple and can be made to run smoothly.
In this context, the “wheel hub” is part of a rear suspension design where the suspension is integrated near the wheel’s mounting area. Packaging the rear suspension into the hub area can reduce the need for frame modifications because the assembly can interface with existing axle/frame parts.
A spring hub is a design where the springs are built into the wheel/hub area. The warning is basically: don’t open it casually, because the springs can snap outward.
Car
Norton featherbed frame
The Norton featherbed frame is a well-known racing motorcycle frame. It’s famous because it was designed to improve how the bike handles, and the team used real testing rather than just theory.
The steering head angle is the angle of the front steering “pivot.” This idea is about keeping that angle from changing too much as the suspension moves, so the bike steers more consistently.
They’re talking about the 1950 TT races (a famous motorcycle event). The point is that Norton used these frame designs on their factory bikes and it paid off in results.
“Twin loops” is a way the frame is shaped. Here it matters because it lets the rear swingarm mount more rigidly, which helps the bike handle more predictably.
This is about how they tested stability by forcing weight onto the front wheel. The point is that putting more load on the front tire made the bike behave more predictably than the other test method.
Term
twin aluminum beam
A “twin aluminum beam” is a frame design that uses two main metal beams made from aluminum. It’s mentioned as a key step toward the modern way bikes are built for stiffness and handling.
A trellis frame is a motorcycle frame built like a metal lattice. It’s designed to be strong and light so the bike feels more stable when you ride hard.
Hydraulic dampers are shock absorbers that use fluid to slow down suspension movement. They help keep the ride from bouncing too much after you hit a bump.
A steering damper is like a stabilizer for the handlebars. It helps prevent the front end from wobbling by adding controlled resistance to steering movement.
Suspension travel is how much the suspension can move up and down. More travel usually means the bike can handle bigger bumps without getting overwhelmed.
They’re saying the suspension can absorb energy much more effectively when it has more movement. Doubling the travel can mean a big jump in how much impact it can handle.
Harshness is when the suspension feels rough or jolt-y instead of smooth. If it’s too harsh, riders can’t go as fast or as hard because it beats them up.
Extended travel means the suspension can move more distance when the wheel hits bumps. It can make the ride smoother over rough ground, but it can also change the bike’s behavior when you ride it hard.
Compression damping is the “shock absorber resistance” when the suspension is being pushed down. It helps control how quickly the suspension compresses after hitting a bump.
Term
limited area
It means the shock absorber forces oil through a small opening. A smaller opening makes the suspension resist movement more.
A progressive compression valve makes the shock “get firmer” as the suspension moves faster. That helps keep the bike controlled when you hit bumps hard or compress the suspension quickly.
Shock rod velocity is how quickly the shock moves in and out. Faster movement usually means a bigger impact, so the shock’s resistance can be tuned to that speed.
An upshift is when you change to a higher gear. It’s often done to keep the engine in the right range as you accelerate.
Topic
Daytona infield banking (turn five)
They’re talking about a specific corner at Daytona where the track surface is banked. The point is that the suspension change helped the rider handle that section better.
Term
front suspension compresses
Front suspension compression is how much the fork moves upward into the chassis when braking loads the front wheel. On motorcycles, this movement changes geometry (like steering head angle) and can also affect traction and stability. The episode uses it to explain why braking can cause a dramatic “nose over” attitude change.
Anti-dive is a motorcycle suspension feature that tries to stop the front end from squatting too much when you brake. Without it, the bike’s front suspension compresses and the handling can feel weird or scary. With anti-dive, braking feels more controlled.
Yamaha is mentioned because the episode claims their bikes could brake better even without anti-dive. The idea is that the bike’s weight shift during braking actually helped prevent the rear wheel from lifting. So riders didn’t need anti-dive anymore.
Front brake torque is the turning force the front brakes create to slow the bike down. During hard braking, that force can help push the bike’s weight forward enough to lift the rear wheel. The episode links this to why anti-dive can let you brake harder without lifting the rear.
A stoppie is when you brake so hard that the rear wheel comes up off the ground. It’s basically the bike trying to pivot around the front contact patch. Riders usually want to avoid it unless they’re doing it on purpose.
Kawasaki is the motorcycle brand credited here with experimenting with an unusual rear-suspension concept called “Fubar.” The mention is relevant because it ties the linkage discussion to a real manufacturer trying to solve acceleration/braking stability problems.
A virtual pivot is a “pretend” rotation point created by the shape of the suspension links. It helps engineers predict how the wheel will move when forces act on the bike.
A-arm geometry is about the shape and mounting points of the suspension arms that guide the wheel. Those angles determine how the wheel moves when you brake or accelerate.
Anti-squat is about limiting how much the rear suspension squats when you accelerate. The idea is to keep the bike/car more level so the tires stay planted.
A Chebyshev linkage is a special set of moving parts that helps turn one kind of motion into another in a controlled way. Here it’s mentioned as a way to make the rear wheel’s movement behave more predictably.
Constant wheelbase is the goal of keeping the distance between the front and rear axles unchanged as the suspension moves. Some suspension designs try to achieve this so handling characteristics don’t shift during bumps, braking, or acceleration.
Chain tension is how tight the drive chain is under load. Because the chain pulls on the rear sprocket, it can tug the swingarm and change how the rear suspension sits.
A tangent force is an “off-angle” pull. If the chain isn’t lined up the right way, it can push or pull the swingarm in a direction that makes the rear suspension extend or compress unintentionally.
Chain slack is the small amount of looseness in the chain. Too much or too little slack can make the chain behave differently as the suspension moves, which can affect how the bike feels and even cause binding.
Car
Yamaha TZ500
The Yamaha TZ500 is a race bike where the drive chain setup really matters. The hosts are saying that as the rear suspension moves, the chain can get too tight in certain positions unless you set the slack carefully.
The chain is under tension, and that tension tugs on the rear wheel area. That tug can make the bike squat or rise differently, depending on throttle and suspension setup.
Twist resistance is how hard it is to twist the frame. A stiffer frame helps the suspension work predictably instead of moving in unwanted ways.
Car
Yamaha TZ 750
The Yamaha TZ 750 is a famous race bike from the two-stroke era. Here it’s mentioned because its acceleration and suspension behavior show what happens when the rear suspension is pushed hard out of a corner.
The upstop is a hard limit that stops the suspension from extending too far. If the bike reaches it, the suspension can’t move further that way, which can affect grip and feel.
Center of mass is the “balance point” of the motorcycle. If that balance point is high, the bike is more likely to tip or lift a wheel when you accelerate.
Wheeling is when the front wheel comes up off the ground. It usually happens when acceleration creates enough force to unload the front tire.
Car
Honda NSR 500
The Honda NSR 500 is a race bike Honda built for Grand Prix competition. The key idea mentioned here is how it was laid out—fuel and exhaust were positioned to help protect the rider and manage heat while racing.
MacPherson strut is a suspension setup that combines the shock absorber and the main mounting point into one unit. It’s popular because it takes up less space, but it may not give the same feel as more specialized designs.
Directional stability means the bike tracks straight and doesn’t start “wandering” or turning on its own. If it’s a problem, the rider has to fight the bike to keep it going where they want.
A telescopic fork is the standard front suspension on many motorcycles—two sliding tubes that compress when you hit bumps. It also affects how the front behaves when you brake hard.
Side-loaded means the fork is being pushed sideways, not just compressed straight up and down. That can make it harder for the front suspension to move smoothly when you brake.
Hard braking is when you slow down very aggressively. That’s when suspension forces get big, and the front end has to keep working correctly to stay planted.
This is about whether the tire stays in contact with the road as the bike moves. If the suspension can’t move freely during braking, the tire may not stay planted as well.
Term
shortest braking distances
Braking distance is how far a bike travels from when you hit the brakes until it stops. The host is saying some suspension designs can help the bike stop in less distance.
Concept
pivoted front suspension
A pivoted front suspension uses linkages and joints to guide how the front wheel moves. The host says this kind of setup can help braking by keeping the front end working in a more controlled way.
A leading link suspension is a way to move the front wheel that keeps it from changing the bike’s “front-to-back” position as much as some other fork designs. That can make the bike feel more stable when the road is rough.
Wheelbase change means the bike’s “front-to-back” spacing effectively shifts when the suspension moves. Some suspension designs try to keep that shift small so the bike doesn’t feel like it’s changing its steering behavior mid-corner.
A hub center front end is a front suspension design that uses a pivot near the wheel’s center instead of the usual fork tubes. It’s meant to keep the front end’s behavior more controlled over bumps.
Car
BMW Tazy
The BMW Tazy is a BMW motorcycle the host brings up as an example of a different kind of front suspension. It’s notable here because it uses a hub-centered front end instead of the usual fork setup.
LIVE
Hello everyone and welcome back to the Cycle World podcast. I'm Mark Hoyer. I'm with Kevin
Cameron. If you've never joined us, thanks for joining us. If you have joined us, like I said,
welcome back. So we recently did a podcast about rear suspension, principally the swing arm.
Had a few little chit-chats in there, but we're going to talk about failures of rear suspension,
and things that we possibly pondered and looked at the sky and thought, what if the wheelbase
never changed? What if constant steering geometry? Imagine perfection.
Imagine perfection and then imagine getting into the dyno cell and putting a connecting rod in the
roof, for example. But yeah, we're going to talk about suspension, the failures of different types
of rear suspensions and all the implications of what we're working on motorcycles here.
Very quickly, if you haven't found us on Patreon, go find us on Patreon. You can get every episode
that we've ever done commercial free plus extra content that Kevin and I are working on every
week and posting every week on Patreon, stuff that's exclusive to subscribers. It's five bucks,
you know, not too bad. And, you know, YouTube's great too. Join us here if you want. Just know
you're paying YouTube a lot more than you're paying us. Oh, no, did I say that? Anyway,
thanks for joining us. Let's get right into rear suspension, Kevin. Okay.
Front suspension came first because if you hit a bump and it's tall enough, it acts as it tries to
wrestle the steering out of your hands. Well, I think there's more natural padding on the other end
too compared to your hands. Well, that's true. Yes, that's true. Except for my
maternal grandmother. But front end needed suspension because otherwise bad things happen
right away. So people learned to ride with front suspension only, so-called rigid frame.
But there were efforts made to add suspension to the rear, most notably Indian in 1912,
who made an effort in that direction, was an option, wasn't a popular one. And
there were a number of attempted swing arm revolutions which failed because, well, I should
say giving rise to the wisdom of the ages, which was nothing steers like a rigid. Now,
the rider, a monopoly of control. You turn the bars,
causes the machine to flop over right or left at your choice. So, but if you have a swing arm
bike with a weak swing arm, then there's a second opinion on steering. Is the throttle
pulling, causing the chain to pull strongly on the swing arm? Are you hitting bumps? Is the frame
flexing? So, what was the good compromise in that period from the creation to 1935 was the
section tire. That was rear suspension, in effect. The same revolution had occurred in
automobile tires. They had learned the comfort producing qualities of not blowing the tires up
to 100 psi. And they began to build thinner walled, larger section tires operating at lower inflation
pressure. I'm a big fan of bringing back the more sidewall. We need tall tires, none of this
Yeah, well, near the end of Goodyear's participation in road racing in 1984,
and right at the end of the two stroke era, there was created, and Dunlop did it too,
tall sidewall tires, because it was believed that if you added some lateral flexibility,
that the motorcycle would be more stable. There would be an opportunity for the flexing rubber
to provide damping force. But that diverts us from our subject, which is rear suspension.
Then came 1935, and two big things happened. One, Phil Vincent in 1929 had bought the name
and a few bags of frame lugs from Howard Davies, who had made his own motorcycle and won the TT on
it. He won the TT on a bike he'd built himself. So Phil Vincent buys it. Phil Vincent as a school
boy was drawing pictures of motorcycle frames. And what he built was a rear suspension that was
triangulated, so that the two beams of the suspension were more resistant to this motion,
which would cause the rear tire to tilt from side to side.
One of those bikes finished seventh in the 1935 TT. And remember, Vincent was never really a factory.
It was more like two creative guys with a lot of helpers.
And the other creative guy, of course, was still Irving. So here's this bike in seventh,
with nothing but factory Norton's and a couple of factory NSUs, which were just German Norton's,
some would say, ahead of it. Distinguished finish. Well, aside from the first place, which was Stanley
Woods on the factory 120-degree V-Twin Moto Guzzi with a triangulated swing arm.
And this was a shock because nothing steers like a rigid. People don't like to find that,
you know, they'll shout not killed. Well, actually, it's okay if the right people tell you to, you
know what I mean? People like to nail down these home truths. So no less an authority on everything
motorcycle-wise than Joe Craig, Norton's long-serving racing manager. In a 1942 magazine article,
he proclaimed that Stanley Woods could not have achieved his stunning last lap in the 1935 TT
on a rigid frame. Suddenly, everybody's got to have rear suspension. Rear suspension is hot. It
won the TT. Well, how can we do this on the cheap? How can we, you know, like make it look like rear
suspension or something like that? And this gave birth to things like sliding pillar. Here comes the
two members, triangulated members of the rear suspension, the hardtail, down to the axle holders.
And instead of just putting the wheel into the axle holders, you make room, weld on some brackets
and put the sliding pillars there and attach the rear axle to them. Presto suspension, not much of it.
It's there. And I got to say my experience with those types of frames is, you know, it's
possibly more comfortable, but perhaps also more unsettling.
Yeah. Well, of course, one of the things is I noticed that that detective dramas on television tend to be
better put together because so many people are working on them. And then along comes a family
comedy and it's, I think I'll go get a sandwich. So the fact that large numbers of people were
working on these concepts eventually made them, made them workable. There was a thing in 1919
called Coulson B. Coulson B, instead of attaching stick, slip, prone sliding pillars, had little
dinky vestigial swing arms at the ends of the hardtail. And the axle, I think, was supposed to
somehow prevent this whole thing from flopping to side to side. Footnote to history, Coulson B.
It went nowhere. So
this was pretty much the state of affairs from 1935 onward, although Vellisette enthusiastically
adopted rear suspension in the form of three pieces of pipe, not welded together, but mechanically
fastened, make those joints good and tight, and you might have less of this.
Never having ridden a Vellisette, I will have to defer to Mark who has not only ridden them, but
to an extreme. While the ridgents were, I had a 37 KSS with a girder fork and it was a pleasure to
ride on a winding road. And you can see, it was, for me, it was the education that took me from,
I'd already owned the KSS, or the MSS, which is the Pushrod 500 single. It was the first
swinging arm 500. I had the 19th bike off the line, in fact, for swinging arm bikes. And
it's a pretty good handling bike of the early 50s, mid 50s, British bikes that I've ridden,
much better than a sprung hub that Triumph was doing. We'll get to that. And that's quite a
contraption. But Vellisette swinging arm was pretty good. And as Kevin was talking about earlier,
getting some of the action, not rigidly connecting the steering head to the axle,
nothing steers like a rigid, they're connected. And that means they're not having a twist,
which Kevin's talking about, introducing rear steering, whether you're braking hard or accelerating
or hitting bumps in the corner and starting to get cycles going, where you just, I rode a Norton
500 twin that was a Model 7. And it was exciting. It was, it was not bad, but I mean, the Vellisette
for the Euro works pretty well, although getting back to it, the single, it had a vestigial seat
post in the middle of the frame, which is what came up between the gearbox and the engine.
And there's a lug for the swing arm pivot, which is a pipe through a lug that's about this wide.
And then you clamp on the swing arm arms, they have little pinch clamps on them. So you have to
pinch them, get them lined up, you know, so that they're not out of a skew. So there's some setup
there and then you clamp them on and it can't have any play in it. And I've, you know, it's,
sometimes you got to sleeve them and then you clamp the thing. I don't know. There's like a kit
Norton's having. Participatory motorcycling. Yeah, you got to really work at it. I mean, that's,
that's why we're here. And you know, there's plenty of stuff you can buy. You never think
about the swing arm pivot for the life of the motorcycle. In any case, they worked okay.
Bellasets worked pretty, the swing arm Bellasets worked pretty darn good. It was a step and it was,
it took some courage, I'm sure. Well, I want to give also one more little bit of credit to
Bellaset was that you could adjust the position of the upper shock mount. They had an arc in the
frame. We'll throw up an image. That famous arc, yes. And what you can do is basically
change how compliant the suspension is by tipping them forward or making them more vertical. And
it would change that physical ratio. And it's, it's useful. I mean, look at the size of me.
It improves the bike. And it was a method of adjustment that no one else had at the time.
Around 1950, Edward Turner did something very characteristic of Edward Turner.
He was the man who, when he designed a parallel twin four triumph, made sure that it would slip
into the frames that were made for the single. Now, this is not lavish manufacturing backed
by the courage of an enormous market. This is mind the pennies and the pounds will take care of
themselves. So what did he do? He designed the rear suspension into the wheel hub
so that it could simply be slipped into the axle carriers of the stock frame,
no modifications, no extra costs. Now, this has been, the spring hub has been referred to as a
jack in the, jack in the box, because if it happens accidentally to open something will spring out,
namely the springs. Well, I was very much told by my friend, the Bill Getty, who's run JRC
Engineering. He's an incredible British bike mechanic and his historical knowledge. He's
worked on everything. He used to run a shop for a long time and now it's aftermarket parts for
British motorcycles. But he said, you know, Mark, if you ever own a spring hub, try not to open it.
As Kevin points out, there can be explosive. The other big development in 1950 was, of course,
the Norton featherbed frame, which was
developed by Rex and Chromie McCandless in Northern Ireland as a result of actual testing.
And rather than armchair platonic theorizing such as we want a constant wheelbase, we must have
constant steering head angle. We must have purity in all things and perfection.
So Norton were so impressed with this thing, they contracted with the McCandless's to build the
frames for the 1950 TT bikes for Norton, the factory Norton's. And they won the TT. And not only that,
they gave the Italian four cylinder bikes a terrible scare because they could get on the gas
earlier in a corner. They were stable. They braked well. And in Norton's testing,
the featherbed version could be written around the outside of their previous bike, the so-called
garden gate frame, which was a single plane frame, similar to that of a bicycle.
The featherbed bed frame had twin loops, and the swing arm was placed between them at the
aft end so that it had a broad base for stiff mounting, not a lot of flopping and flexing.
And Jeff Duke would have won the World Championship on that bike first time out, except for tire
failures, chunking at high speed. So, and then in 1951, he did win the World Championship,
the last one that Norton would win in 500 or other classes. The singles were not finished,
but almost. However, the terror felt by the Italians resulted in a widespread
Nortonizing campaign. What is it about this bike that makes it so able? We'd like to have some of
that. And of course, the great ambition of English riders was to be summoned to Italy and be well
paid to arrive and to ride the frightening force. And they would bring with them, in their suitcases,
British made telescopic coilover rear suspension dampers inspired by those made by hand by the
McCandless Brothers, which included remote reservoirs, not to be seen again for 20 odd years.
So, this was a movement of goalposts. This set the scene for 20 years of convention,
in which if you wanted a good handling motorcycle, you would buy one of these Nortons with the
featherbed chassis, and you would try to understand it. And of course, it wasn't so mysterious.
McCandless moved the rider and the engine forward almost three inches. Big change. And
I've spoken to you before about the JSME article in which they ran
motorcycles stationary on a moving belt highway. And they tested them for stability,
and they found out that loading the front tire rather than the European practice of backing
the engine up against the rear tire produced stability and steering that did what you expected.
So, this was the new standard. And it would rule the world until the coming of Antonio Cobas and his
inventions in the early 1980s, which culminated in the twin aluminum beam
establishment of the present moment. Not to overlook the significance of so-called
trellis frames as practiced by Ducati. KTM also was an adherent of multi-tube space frames.
So, one of the very important things that Norton added was supple, smooth acting,
hydraulic dampers front and rear, telescopic fork in the front, twin shocks in the rear.
No more stick slip from scissors type dry friction dampers, which had been the world standard since
there was rear suspension. Sort of like a clutch. And before that it was used on on girder forks.
Yeah, you sort of sort of like a clutch, except it had two arms on it that were attached to
different elements. And that was your, you know, attached to the front wheel, attached to a fixed
area. And in some of them there was a big wing nut by which you had adjustable damping.
Steering dampers were like that for a time. You had a big knob. You could turn on your steering
head and the rod went through to it. Right into the 60s. Yep, to essentially the same
friction pack underneath the steering pivot, so.
Well, in 1973, there was an explosion of rear suspension innovation from Motocross.
And this is where suspension is so badly needed, so it's not a surprise that innovation
should come, should well up out of the dirt, so to speak. And
what had been the norm for many years was the three to three and a half inches of travel
of a pair of trusty old black curling shocks with a variety of springs that you could get
at your nearby stockists. And stockists. I've always liked that. I'm not going to say it again,
don't worry. Riders rode as hard as they could with those short travel units.
When they began to extend the travel, they found they could go much faster. Now, one reason is
that the energy absorption ability of a suspension is proportional to travel
squared. Double the travel, you can absorb four times the energy of the shorter travel unit.
And the other thing was that, as pointed out by former American Honda Racing Manager,
Gary Mathers, riders push as hard as they can, but they are stopped by what they call harshness.
And whether that means that your brain is being jarred into foolishness,
or that your muscles are unable to go any further in the direction they're going,
or your peripheral circulation shuts down, I don't know what it is. I'm sure that
sports physiologists could tell you what harshness is. But what happened was that as they
extended travel, at first everyone enjoyed the softer suspension and the ability to
magically travel at great speed over rough terrain. But as usual, people rode to their limit,
the harshness limit. So Mathers noted, they ended up with the same spring rate with 12 inches of
travel that they had had with three and a half inches. And I find that fascinating.
Well, racers, the good racers, what do they do? They follow any tester. You ride the bike until
it does something wrong. You push it harder and harder until it does something wrong. That's
actually the job. Because most things are good. That's 70%, 80%. Most things are pretty darn good.
But it's when you started asking me more. Long travel hit road racing too. And
one rider told me that with his long travel Honda with suspension that had the latest in low
rigidity compression damping. Traditional compression damping was just a hole through
which oil was pumped by the moving piston in the damper. What a suspension damper does is it converts
bump energy into the velocity of oil rushing through a limited area, in this case a drilled hole.
And the resistance to that flow goes up as the square of the flow, which means at some level,
the resistance becomes essentially rigidity. And there's all kinds of wonderful stories about
riders throwing shocks into into lakes or abusing them in other ways. But what this led to was a
new type of compression valve that was progressive. And that whose resistance was more nearly
proportional to shock rod velocity than to the square. And so this made it possible for
the rider I'm talking about to hit the banking at what used to be turn five out of the Daytona
infield up onto the banking without timing it to coincide with an upshift. He could just ride
through there on the power with this innovation. So this is not engineers playing with pencils and
papers. This is let's try this. Be sure to wind your stopwatch. Okay, here we go. Oh, that's much
better. Let's talk to the rider and so on. This is how it actually goes. We are not sitting in
Plato's cave looking at mere shadows of reality. We're getting in there and messing with it. So
we get results this way. Now there are some exceptions. The atomic bomb worked perfectly
the first time. Although there have been some fizzles since then. Well, the atmosphere didn't
even catch on fire either. That was one. No, hydrogen and oxygen failed to rush into each
other's arms. But it was a sort of nagging itch until they actually saw the fireball through
their smoked goggles. So when long travel hit road racing and street bikes, of course what
people noticed was these bikes have powerful brakes and pavement has more grip than dirt.
Which means you brake and the bike noses over rather radically.
And for each inch that the front suspension compresses, you lose roughly one degree of
your steering head angle. Now this is there are people who say that this can be a terrifying
thing and then there are others who dismiss it. But I've not risen to those
heights in my own modest motorcycling. So people began to say let's put a stop to this
extreme attitude change. We don't want to go back to short travel. Let's put anti-dive
onto the front end. And hydraulic, mechanical, there was a wide variety of devices. You may
have seen the Kawasaki ones that had all these levers which used the effort of the brake caliper
to follow the brake disc to generate a force that lifted the front of the machine.
Now Udo Giedel has commented that it could brake nicely or on a rough surface it could stutter horribly.
Then in the end once again reality prevailed because it was found,
wait a minute, these guys over at Yamaha are out braking our guys and they don't have any
anti-dive on their bike. What do they know that we don't? Well what they knew was that when the
front of the bike sinks dramatically it takes the center of gravity down with it. And that makes
the lever, the height of the center of gravity over the pavement by which front brake torque
can lift the rear wheel into a stoppie makes the lever shorter so you can brake harder
and not lift the rear wheel. And so overnight anti-dive just disappeared went off the street
bikes it was all gone. So embarrassing. And this is how things go. There was initial resistance
to monoplanes. I mean where the bracing where well they're inside the wing so to speak.
But I don't really trust that. I mean the biplane is built like a box kite you know you can trust it.
They didn't like a canopy over the pilot because he couldn't feel the slide slip on his cheeks
and judge how the turning was going. Well I mean imagine a Cessna 195 in the late 40s with no
wing braces no it just it just was a straight wing sticking out and there was no nothing
visibly holding it.
Well anti-dive disappeared okay. There were various strange anomaly anomalous
suspension proposals from like 1970s onward. And US Kawasaki played with what they called the
Fubar rear suspension. There were two swing arms going up and down together. Their aft ends joined
by an upright that was perforated for the rear axle. When they described this to me it sounded like
someone slightly familiar with the A-arm geometry of race cars had fallen in love with the idea of
the virtual pivot that is far away in space and so what was hoped for initially from this design
was that it would absolutely prevent wheelies allowing you to just scoot out of corners and
disappear. But in practical sense I think they discovered anti-squat and they actually put this
on a van de Hamels race bikes air-cooled and liquid cooled from 73 to maybe 77.
And then it disappeared they it didn't go any further but they put a lot of effort into it.
Another possibility which I've never seen in the aluminum and steel is the
Chebyshev linkage. In 1859
Pavnuti Chebyshev a Russian mathematician was trying to devise a way to change straight line
motion into rotary motion and in the process he came up with twin swing arms that were crossed.
This was perfect for the constant wheelbase theorists because at last you could have the rear
axle going up and down in a straight line zero wheelbase change. Perfection is at hand.
I don't even know if any prototype of this kind was built but there was the idea.
So what a lot of these ideas for rear suspension were trying to do can be broken down into three
areas. One is people were beginning to be aware as engines grew more powerful remember the two
strokes came to Daytona with 100 horsepower in 1972 that got people thinking. Chain force had an
effect on rear suspension it might either cause it to rise up or to squat down. And so people were
trying to negate this force so that it would be neutral. Hossack's rear suspension he wanted the
swing arm center plane of the swing arm to be horizontal he wanted the chain above it to be
horizontal and parallel with the pavement. ATK came out with a similar idea they placed two
sprockets clamped one above the other to the chain side swing arm beam and they were arranged at
such a height that the upper chain run and the lower chain run when either of them was under
tension would be parallel with the swing arm. So there would not be this tangent force
tending to cause the swing arm to extend. The thing that I loved about ATK was that they
made a demonstration toy was fascinating to play with you could you could change the variables
so that was bad normal thing whether rear suspension extends or it would be super modern
with no net force no effect from the chain tension on rear swing arm height suspension height.
Then the the second idea was no rather than setting the swing arm free from chain pull
let's use the chain pull on these powerful motorcycles which otherwise will squat down
in the rear when they accelerate let's use it to generate the lift force just to the point
that it cancels the squat so that here you are in the turn trying to accelerate and as you twist
the throttle and the rear end squats down weight comes off the front tire and goes on to the rear
tire and the front tire pushes you head for the outside this is squat and push
and I remember seeing one of the South American lads who made it big in GP racing
come in to his crew and make the universal sign for push which is
millibars crossing yes yes and which is now called something else they call it
closing closing the front end and then the third possibility was to
completely ignore all of the above and focus only on constant chain slack because
there are some peculiar motorcycles out there Yamaha's TZ500 you had to be careful adjusting
the rear chain slack because there was a place in the arc of the rear suspension where it got real
tight that's where you had to adjust it and so these guys were going to to nail down constant
chain tension by making the swing arm pivot concentric with the output sprocket centerline
famous spawn in chassis's got that and then BMW was playing with that on their dirt bike which
didn't work out too well for them it didn't work out too well for anyone because it completely
ignores the chain pull effect on rear suspension height and but it's invented several times each
year and it probably will be as long as the motorcycle exists hey here's a good idea why
don't they do this but it's not a good idea it works it achieves its purpose but it ignores
effects that cannot be ignored on powerful motorcycles
so all these uh well then then there's Haasek Haasek was involved in formula one
development and at one point they had a chassis bolted to the wall and they had a
great big bar through the the projecting end and they were going to test that the twist resistance
in pounds per degree and this is good this is this is finding out stuff you want to know by
lashing up something that doesn't cost a million and a half dollars and has to come from a German
high precision outfit um bathroom scale and the drill press uh you got it test your spring
right so it's a famous picture of dam dirt dam drainage suspension springs you got it so um
um
I once uh stood just off of um what used to be turn nine at Laguna the left hairpin
and watched the tz 750's upshift off of that corner as soon as the clutch went home
clunk the bike rose up and hit the upstop they had plenty of anti-squat
this is why um in the early 90s adjustable swing arm pivots began to be seen
adjustable height usually in the form of a rectangular opening on either side of the frame
into which plugged a plate with a hole for the swing arm pivot at a particular height
and you had a fifth case of these like fine cigars and you could select the ones that had
the height change that you thought would put an end to all your problems and shut your rider up
with all his complaining whiners so uh that was
that was that when it came to foobar uh nothing is going to change the fact that the thrust
accelerating the motorcycle is at ground level whereas the center of mass is maybe 20 22 inches
above that what that means is the thrust is tending through this lever arm to exert a torque
on the chassis and lift the front wheel off so what you need to prevent this is either a chaperral
like um big suction fan up front that is pulling the front end down onto the pavement or winglets
or a tiny rocket motor that fires only when you accelerate nothing else is going to stop wheeling
no complexity of linkage gears cams and linkages forget that now here come the elf alternative
motorcycles at first andre de cortons a frenchman uh with formula one experience
reason very reasonably there must be with all the research done in formula one
concepts that are immediately applicable to the motorcycle that poor primitive creation
which will greatly improve it and i will be a star well one of their improvements was
everyone knows that a motorcycle handles better if it has a low center of gravity right wrong
look at modern motorcycles you will see that the rider is way up in the air above the rear tire
it used to be that the seat back the underside of it was arranged to be barely greater than the
suspension travel and many a motorcycle had tire burns on the underside of the seat pan
they found that that didn't work well well honda bought into elf because they wanted to be
in a position of advantage and this looked like it in 1984 they brought their
uh
nsr 500 their new four-cylinder bike two-day tona with the fuel carried under the engine
and with the exhaust pipes routed over the top protecting the rider by means of an insulated
dummy tank and it was found out they added they used this concept on their 500 gp bike
as their main they placed all their bets on this and freddy spencer said i can't
change direction as quickly on the bike with the fuel on the bottom as i can on my old three cylinder
and a test was arranged orange cones created a slalom the three cylinder was sent through
the slalom until freddy said that's about all i can do and clicked they had a measure
they sent the nsr 500 into the slalom at freddy's entry speed and knocked all the cones down
actual physical testing not just sitting by at fireside in a comfortable armchair reading
plateau actual testing revolutionary so that was the end of that it was also the
end of the courtesans they brought in two other fellows instead and this is an excellent story
because it shows persistence willingness to spend money
and ultimately acceptance of the fact that it added up to nothing
but that's something learned so what went on there was that the radical bike
didn't go as well as some bikes modified to be somewhat less radical and so they went in that
direction and all the hub center business with gears cams and linkages gave way to a simple
almost like i'm at first and strut and the poor guy on the bike is trying to give good feedback
and get good finishes and he was fifth or third or he had some good finished positions in the
championship in the middle 80s so it can't be it was ron haslam
very earnest a corner speed rider the bikes wheelbase kept getting longer and longer they
started at 53 inches and they ended up at 57 plus and when uh what was it scott redding i'm not
sure which rider it was told me about the difference the physical difference in the
motorcycle from a corner speed bike to a point and shoot bike he said the corner speed bike is
long and low and that's what honda built for ron haslam and of course as the bike became more
conventional people had heard of macpherson strut and a lot of people were driving cars with it
the extremists squeaked and moaned because it wasn't radical enough it was not true to the
original concept of changing everything wait a minute what are we trying to accomplish here
to annoy people or to win races so uh that just didn't work at one point
a quote on from a rider was directional stability a problem at almost any speed
that's for elf 2a for elf 2c uh front pattern of terrifying proportions but braking was
exceptionally good because you know that a telescopic fork side loaded by a braking force
operating on a long leverage tends to bind tends to cause addiction that prevents the
front end from following the pavement surface during hard braking but with a pivoted front end
no addiction excellent grip shortest braking distances and when harley built their
retro leading link suspension i went to interview the engineer who had done the project and he was
sort of apologetic and i said well i want you to tell me there's got to be some point of superiority
here and i want you to tell me about it well he said um it does have the shortest braking distance
of any bike we make and this is what you would expect from a pivoted front suspension so
there was a point of advantage but it wasn't enough to win races and honda pulled out of the
elf honda thing and no more was heard about it so tough one
so
then we have
leading link
bmw made long leading link earls forks for their flat twins in the early post-war years
and for a number of years during that period uh and the thing about leading link is that
instead of going up and back the way the wheel does with the telescopic fork it goes
nearly up and down with very little wheelbase change now how you can
stiffen this assembly of two little leading links it's kind of like koulson b so that the
wheel doesn't cock from side to side as you go through a turn with bumps in it i don't know
but kutzi managed to win the 350 world championship five times in a row 1953 through 57
and then they pulled out of racing and that was that bmw kind of like the emperor has no clothes
they finally realized marketing realized that the graceful waving of the front end on those
so that came to an end it's an historical footnote it was an era
was an attempt to find a better way to do it
so then there was the bmw tazy um early what 90 1990 i think it was shown the cologne
and it has a hub center front end on it if you're not familiar with a hub center imagine
a drum like open at the ends a ring that is spoked into a rim then imagine two large bearings
inside that empty drum with another drum pushed through it and the drum that's pushed through
it has a kingpin and grasping the bearings from one or both sides by reaching in through the
open ends of the drum is a front swinger now the only thing that steers is the wheel the disks
and the brake calipers there are no ponderous fork tubes swaying from side to side with the wheel
and this is potentially a strong point of this hub steering because it is more resistant to wobble
wobble is a rapid oscillation of the front wheel which generally times out at about 40 or 45 miles
an hour or if you put your hands back on the bars if you have uncertain motorcycles decided to
do the snaps on your gloves oh yes i won't do that again um life's little travails
so the the tasey i wanted to succeed because it looked right we all did and the frame the frame is
just a a thing that went from the frame was the engine it went from the front swing arm pivot
to the rear swing arm pivot there was no steering head up in the air with long poles going down
just little arms delicate little steering arms to get down there of course the the front swing
arm had to have elbows to provide clearance for the front tire and this was a problem for uh
ron haslam at one point on the number three elf honda bike because going through i think a left
hander um and he used a lot of lean angle he was a corner speed stylist he dragged the swing arm
on the pavement not many can make this claim so this stuff
came to an end uh tasey
i encountered a man who liked the tasey that he bought so much that he bought two more
so that he would have one at each of his three residences and he was a
cheerful guy who just loved his motorcycle so he had three of them the other neat they are cool
you know i don't know if i need three but they are it is a charming thing but uh the thing is
there are a lot of ways to build a motorcycle that will chuck along the highway
and get you where you're going and provide you with a sporty feeling but
with that i'm sure for example that we could build a lovely chassis of adequate stiffness
out of steamed plywood but when you push something to its limits you learn other things and racing
riders on racers on tasey or similar bikes found the steering vague they complained of lack of
feedback well the information it was like that story about um owl a tiny creature a mouse went
by owl's house and he heard a commotion and he told his friend owl was up in there throwing the
furniture out of the windows and stomping in the bottoms of all his pots and pans when the signal
is transmitted through several repeaters the signal at the end may not be the same as the
signal at the beginning and so they said if there are gears cams and linkages heim joints
rose joints uh things that have to be lubricated with a grease gun it's going to take the feel
out of the front end but like mark says it's a perfectly adequate motorcycle in other respects
but it failed to make a revolution there was no reason to build it that way having to do with
superior performance other than i'm sure it has a good braking distance
so this is uh this brings us to the present moment when uh i was in the press room at
valencia once and a gentleman came over to show me a project that he was uh i think a
machine shop instructor and he and his lads were building a high tech front end for a motorcycle and
i said well now i'm puzzled because people call this high tech but it has never been adopted
at the highest level of motorcycling which is uh world supers motor gp etc oh he said i'm
perfectly aware of that but my class want to build this oh okay fine that's that's okay
but this continues journalism loves to call complex things high tech extra parts
like the nasa guy said if you have a million parts and the reliability of each one is
a million chances a million times it flies and one time it fails you're gonna have a failure every
time so reduce the number of parts simplicity yeah there been this was the lesson that i took from
all of these complexities which is that the motorcycle can't go too far from being two wheels
an engine and a place to sit
and what the mechanist brothers created hydraulic damping at both ends of a strong frame with a
well founded uh swing arm telescopic four cup front it's still not wrong
so all of these excursions have been instructive but they have failed to produce a revolution
some of these bikes um what was the name of the yamaha that uh was built with a with a strange
front end the gts 1000 had the omega frame and um i'm forgetting that fella's name who put it
together it was his idea he was a big proponent um my brain my brain was actually recently
diverted by thinking back to the moto sizz with the the variable trail inserts and the not tell
the flex adjustable fork on that that was a interesting time as well um that that could
be part of a podcast in and of itself well there are people who've devoted years of their
lives to these projects and we have to respect that um but it does turn out sometimes like
carrying the fuel under the engine it just doesn't work why didn't it work because people were
confusing the sense of security that they have on a heavy motorcycle if it has a low center of
gravity like a harley big twin confusing that with a low center of gravity on some a sporting
motorcycle because as it turns out people imagined if this is the ground plane and this is the
motorcycle people imagine that the motorcycle pivoted around the line of contact of the two
tire footprints it does not instead what happens is the bottom of the motorcycle
goes one way and the top of the motorcycle goes the other so what does it do it rotates around
its own center of mass when i was learning to ride faster and riding more and more hours i
discovered that because you would see an object in the road you wanted to avoid and you didn't
steer around it per se the center of gravity can could continue in very nearly the same direction
it was going but you would swing you would actually swing the wheels out of the way it reminds me
of sports the center of gravity of the motorcycle wants to travel in a
relatively smooth line and things are pivoting around it your wheels are going out the rider
is doing things to alter where that center may be but you're you're trying to carry the center
in a nice smooth manner down the road well it insists yeah and it does and you don't want to
well you have to and like how do we best control it reminds me of sports if you look at a surfer
doing crazy things on a wave if you follow the path of their head their head is relatively stable
because it's just like the squirrel when the squirrel gets flung out of a tree the first thing
it does is it's could be flailing about it's sighting its landing and then it's rotating its
its head is everything and that's just that's sort of where the center of mass is in in a bike you
swing the wheels out just as as you were describing you need to miss the screw you see something you
just go you turn a little bit you get the bike swung and then yeah you allow it to get the wheels
around the outside of it and hope you don't hit what you're trying to avoid but yeah and return
to equilibrium yeah and it's what right back under his yep so it's um it's not intuitive
unless you um have a little familiarity with Isaac Newton and his his work
he seems to have been a peculiar fellow yeah he complained once that all my friends he said
are constantly trying to embroil me with women
so Newton's laws are just what we found happens most frequently
and we call that a law it's more of an expectation and well so what was happening when they put the
fuel on the bottom is they moved it away from the center of mass therefore changing what was more
like a cannon a 24 pound cannonball into something that was more like a 12 foot long
24 pound ladder you're moving masses away from the center of mass so that Freddy's efforts to
change direction produce less result so then they took the gas out and put in two quarts
and they put 32 pounds of ballast up among the pipes and Freddy went sailing through
the orange cones without knocking down one so um good stuff I um I'm pleased with that well you
uh like in many things in life mythology is very easy to uh say is you know yeah
that's how it is just like you talked about moving the engine to the rear
no I got to get traction we got to get traction and drive you know all that stuff
and um McCann's brother's doing science testing actual things and really just
check your prejudice at the door forget your bias just look at what's going on
and you know whatever it is engine building look at the marks on the bearings look at
measure the temperatures I don't know you just send the oil in for analysis what's
what where particles are in there truly so companies do it all the time I'm a firm believer
I got my little black bottles and uh you know I rebuilt the engine of my Ford 460
and it's relatively low miles and I know what the service interval is recommended
and I changed the oil and I've I've got a vial that I'm going to send in and I did it at the
interval and I'm gonna see what happened knowing how I drove it knowing that it's relatively new
but I'll track it and it's it's relatively inexpensive but it gives you actual information
it's not just as you pointed out we talked about oil change interval and I actually I believe the
first time I had this comment from you was reading your book the sport bike performance handbook
it's a great book if you can find it and it's my first try Kevin it's a nice book it's got
hand drawn graphs all kinds of neat stuff that's very artisanal and I like it I loved it actually
it was a craft paper and and one of the things that one of the things that you said in that book
about oil change interval was well you could change your oil every 10 minutes and wouldn't that be
something it was along those lines about frequency of oil change so it's good to know the truth if
you if you can go to the effort and spend the money you know spend I think it's 40 bucks or
something you can send a nice big oil sample in and get some actual data the sensor that
causes the change oil soon light to illuminate what does it measure is it measuring oiliness
oh this oil is terrible does it measure viscosity maybe the viscosity improvement agency agents are
uh which began life with long chains have now become little short things no what it measures
is the presence of anti-wear because as long as there's anti-wear in the oil additive that has
not yet been consumed in the process of protecting metals from each other when they come very close
what that additive does is it produces a sacrificial solid lubricant layer which is scuffed away but
it immediately reforms because that area is hot and the additive it's still in the oil says oh
here's my chance and as long as there's anti-wear additive in the oil uh it is not worn out now there
is another phenomenon called falling out of grade which is exactly what i mentioned before namely
the vi improver is a long chain chain molecule viscosity index vi yes like like um i think of
of oil is like a pot of boiling spaghetti and when you want to thicken a light oil in order to have a
multi-grade 5 w 20 for example you start with five and you boost it to 20 by putting these
long chain molecules into it now if those molecules are not the high quality kind and i forget which
one that is they can break they can lose molecular length and then what happens is called falling
out of grade it's becoming more like a 5 w 5 than a 5 w 20 and you don't i think i took that out of
my pressure washer because i bought a used pressure washer and i don't think they ever change the oil
but also i think the carburetor may have been putting fuel into the oil as well so it was
definitely out of grade and we're um off the subject here but i was just thinking that but you
know we we were talking about trying to know the truth and that's what we uh that's why we send
our oil in at least once in a while and uh to find out what's going on see what's in it and um
well there were those uh there was that b 29 crew who were refusing to fly and a jeep comes up
and screeches to a halt and a red faced officer piles out you will fly that airplane and someone
said yes but uh they gave us engines from bendelair depot i'll have you know that those
bendelair depot engines are just as good as the ones that come from new jersey and he's
ranting and raving meanwhile the pilot has said to the flight engineer you want to go
pull the screens on number three and he's out there doing it and the red face is getting redder
and redder court marshall is about to convene at least in his imagination and here comes the
flight engineer with the screen with bolt heads and pieces of piston ring on it and he
oh i'll fly that no i won't i'll fly it myself yes sir you first know i know i've told that story
before but it's a good one well and you know i haven't agreed oil it's a crude form of oil
analysis pull the screen and see what's on it well cut open your oil filter yep yeah the nascar
nascar guy's cutting the filter open oh no is yeah i mean you can stretch out the paper to see
what's on oh yeah the lab the lab that that does the uh oil analysis for the stuff that i send in
you can also send a filter in and they'll uh they'll dismantle it for you but you could just cut
it open you can get your big pipe cutter and cut your uh can off i mean i i have the fortune of
having so many canister filters in my life i don't have to cut the can off because it just comes off
and makes a mess anyway even the toyota the newer the newer toyota that we drive has a canister oil
filter i thought i'd never get away from it and i guess i haven't but um it is it's good to try and
find the truth well that's if yeah that's it we uh we covered swing arms both front and rear and
alternative alternatives uh we we managed to skip um dr john wittner a little bit of him on his uh
slightly yeah well we'll get to him i think john wittner could be his own podcast
well he sure could yeah there's so so much going on there and the allegiance his father was an aeronautical
engineer and a very practical one oh good see that makes sense doesn't that make sense yes
but uh hasik and there was the troll front end uh troll engineering that was kind of like a
oh consider your tracks on your closet door but for giant doors and the metal rollers and it had
this blade with v's on either side of it it had wheels that located it and there were rolling
elements instead of a linear bearing yeah and i rode one of those it had a very rigid
tubular front end and kind of like almost a miniature trellis that was uh fascinating to
we have we have a podcasted about some of that stuff but um we'll see you soon dr.
wittner thank you for riding with us when you get to us thanks everybody for checking us out
and uh we will catch you next time
About this episode
Rear-suspension ideas get dissected through the lens of failure modes and handling: from early rigid-frame experiments and sliding-pillar concepts to swingarm pivot stiffness, tire “suspension” compliance, and triangulated designs. The discussion then follows how racers tuned geometry—shock mount placement, featherbed frame mounting, and damping evolution from dry friction to hydraulic valves. Later sections critique linkage and chain-force approaches (anti-squat, chain pull, adjustable pivots), and broaden into suspension control limits, anti-dive, and even front-end stability and oil-analysis engineering parallels.
Find us on Patreon! https://www.patreon.com/cw/CycleWorldPodcast
How have we gotten in wrong with rear-suspension designs? In so many ways! Kevin and Mark take a tour through rear suspension systems that didn't work and never beat the simplicity of the conventional swingarm, plus they get into all kinds of other elements of the chassis.
