Rear Suspension Designs That Failed, and, of course, More!

A swingarm is the rear suspension arm that pivots to allow the rear wheel to move up and down. Many motorcycle rear-suspension designs either use a swingarm directly or evolve from it, so failures in swingarm setups can strongly affect ride quality and stability.

“Constant steering geometry” means the motorcycle’s steering angles and relationships (like how the front end is aligned) stay the same as the suspension moves. That matters because suspension travel can change rake/trail and how the bike turns, so designers aim to minimize that variation.

The wheelbase is the distance between the front and rear wheel contact patches. The hosts’ “what if the wheelbase never changed” thought experiment points to how suspension movement and geometry changes can alter handling characteristics.

A rigid frame is a motorcycle setup where the rear suspension is essentially absent, so the frame and rear wheel don’t move relative to each other over bumps. The episode contrasts this with later rear-suspension attempts, noting that riders initially adapted to front suspension only.

Indian is a motorcycle brand that, according to the hosts, tried offering rear suspension as early as 1912. In the context of this episode, it’s used as an example of early experimentation with rear-suspension designs that didn’t catch on.

In this context, throttle refers to how much you open the engine’s control (how much power you request). On a motorcycle, throttle changes can load the drivetrain and chain, which can influence how the swing arm and rear suspension behave.

Frame flexing is when the motorcycle’s frame bends or twists under load instead of staying rigid. That movement can change suspension geometry and steering feel, making the bike less predictable over bumps or during acceleration/braking.

A section tire is a tire sized and shaped by its width (“section”) and sidewall profile, which affects how much it can deform. In early motorcycle suspension discussions, the tire’s compliance effectively acted like part of the suspension’s rear-suspension behavior.

“100 psi” is tire pressure—how much air is inside the tire. The speaker’s point is that running lower pressure and using thinner sidewalls lets the tire deform more, improving ride compliance compared with overinflating.

The sidewall is the tire’s vertical rubber section between the tread and the bead. Sidewall height (taller vs low-profile) changes how much the tire can flex, which affects both comfort and how the tire contributes to suspension-like damping.

Low-profile tires have a shorter sidewall relative to their width. That typically reduces tire flex, which can make the ride feel firmer and changes how much the tire contributes to damping compared with taller sidewalls.

Goodyear is a major tire brand, and the speaker connects its involvement in road racing to the development of tall sidewall tires. In racing, tire construction choices can be driven by stability and compliance goals.

The “two stroke era” refers to a period when many competitive motorcycles used two-stroke engines. Two-stroke bikes often have different power delivery and engine characteristics than four-strokes, which can influence how riders and engineers think about chassis and tire behavior.

Dunlop is a tire brand known for motorsport involvement. The speaker notes that Dunlop also developed tall sidewall tires around the same period, based on the belief that extra tire flex could improve stability.

Lateral flexibility means the tire can deform sideways under load. The speaker’s claim is that adding lateral compliance can help stability by allowing the rubber to move in a controlled way and generate damping forces.

Damping force is the resistance to motion that slows down how quickly suspension components (or tires) move. Here, the speaker argues that tire flexing can create damping-like behavior, reducing oscillations over bumps or disturbances.

Vincent (Phil Vincent) is tied to a classic motorcycle rear-suspension design discussed in the segment. The speaker describes a triangulated rear suspension intended to resist side-to-side rear-wheel tilting, and notes a strong finish at the 1935 TT.

A triangulated rear suspension uses geometry that forms triangles to resist unwanted movement. Triangulation increases stiffness against certain motions, helping prevent the rear wheel from tilting side-to-side under load.

Tilting the rear tire side-to-side means the wheel’s contact patch angle changes laterally as the suspension moves. That can alter traction and steering behavior, which is why engineers try to control rear-suspension motion.

NSU is a motorcycle brand (German) that competed in the same era as other factory teams. The speaker frames NSUs as comparable to Nortons in competitive standing, giving context to the 1935 TT results.

Norton is a motorcycle brand associated with classic British racing. The speaker contrasts a Vincent bike’s result against factory Norton machines, highlighting the competitive context of the rear-suspension design.

Rear suspension is the system that allows the rear wheel to move relative to the frame, improving traction and ride comfort over bumps. In this episode, it’s treated as a major design shift after racing results, and the hosts discuss how manufacturers tried to copy the benefits cheaply.

“TT” refers to the Isle of Man Tourist Trophy, a famous motorcycle road-racing event known for high-speed sections and challenging handling demands. The segment uses TT results to argue that rear suspension became a “must-have” after riders proved it could help lap times.

Sliding pillar is an early rear-suspension concept where the axle is carried on pillars that slide within brackets, allowing some vertical movement. The segment describes how builders welded brackets onto a hardtail and attached the rear axle to these sliding pillars to create “presto suspension.”

A hardtail is a motorcycle frame design without rear suspension—so the rear wheel is effectively rigidly connected to the frame. In the segment, the sliding-pillar idea is described as being built “down to the axle holders” from a hardtail base.

A girder fork is a motorcycle front suspension design that uses a rigid, beam-like structure (often with multiple braces) instead of a conventional telescopic fork. It was common on older bikes and can change steering feel and how the front end absorbs bumps.

A swinging arm (swingarm) is a rear suspension arm that pivots at one end and carries the rear wheel. Because it allows controlled movement relative to the frame, it can improve traction and handling over bumps compared with rigid or simpler setups.

A sprung hub is a suspension concept where the wheel’s hub contains springs to absorb road shocks. Compared with swingarm-style suspension, it can change ride comfort and how the bike maintains traction during cornering and bumps.

Rigidly connecting the steering head to the axle would mean the front end can’t allow independent movement between steering and suspension. The speaker argues that this kind of rigidity changes how the bike handles because it affects how the chassis can twist and react to road inputs.

Rear steering refers to a handling effect where the rear wheel’s direction changes slightly due to suspension geometry and movement, rather than only from the rider’s steering input. The speaker links it to conditions like braking, accelerating, and cornering bumps.

Pinch clamps are clamp-style fasteners that squeeze components together to hold alignment and prevent movement. In this context, the speaker describes using pinch clamps on the swingarm arms to ensure the pivot assembly has no misalignment or play.

The upper shock mount is the point where the rear shock absorber attaches to the frame. Changing its position alters the shock’s leverage and the suspension’s effective motion ratio, which changes how much the bike compresses for a given wheel movement.

Motion ratio is the relationship between wheel movement and suspension component movement. If you tip the shock mount forward or make it more vertical, you change that ratio, which effectively changes the suspension’s springing and how progressive or linear the response feels.

A parallel twin is an engine layout where two cylinders sit side-by-side and share a common crankshaft. It’s a common motorcycle configuration because it’s compact and can be tuned for smooth, tractable power delivery.

Axle carriers are the frame-mounted structures that hold the rear axle in position. If a suspension assembly can bolt into the axle carriers, it can often be installed without changing the rest of the frame.

A spring hub is a suspension design where the springs are housed in/around the hub area rather than only in a conventional rear shock location. The “jack-in-the-box” comparison highlights that opening it can release stored spring energy quickly.

The Norton featherbed frame is a famous motorcycle racing frame known for its handling-focused geometry and stiffness. In the segment, it’s tied to the idea of testing-driven development—using actual results to refine steering and wheelbase behavior for racing.

Constant steering head angle is a geometry target where the angle of the steering axis remains effectively unchanged as the bike moves. Keeping that angle stable can help preserve steering feel and predictability under braking, bumps, and suspension travel.

This segment discusses the 1950 Isle of Man TT racing effort, specifically Norton factory bikes built using the featherbed frame. It’s a historical racing context for why the frame design mattered.

“Twin loops” describes a specific motorcycle frame geometry where the frame forms two loop-like sections. In this context, it’s used to explain how the swingarm can be mounted between them for a stiffer, more stable rear suspension attachment.

Remote reservoirs are extra oil chambers connected to a shock absorber. They increase oil capacity and can reduce fade by keeping the damping fluid cooler and more stable during repeated or high-load riding.

In motorcycle stability testing, “loading the front tire” means applying weight and forces to the front contact patch to influence steering and balance. The segment contrasts this with a European approach of backing the engine up against the rear tire, arguing that front-tire loading produced stability and steering that matched expectations.

A “twin aluminum beam” refers to a motorcycle frame approach using two aluminum beams as the main structural members. The segment frames this as the evolution toward the modern standard, implying improved rigidity and packaging compared with earlier designs.

A trellis frame is a motorcycle chassis made from multiple small-diameter tubes welded into a lattice. It’s valued for being relatively light and stiff, which helps the bike handle predictably under load.

Hydraulic dampers use fluid resistance to control how quickly suspension components move. That damping helps reduce oscillations and keeps the tire in contact with the road over bumps.

Twin shocks are two rear suspension units, typically mounted on either side of the wheel or swingarm. Compared with a single shock, they can package differently and may affect how the rear end moves under braking and bumps.

Stick-slip is a suspension behavior where friction alternates between sticking and slipping, causing jerky motion instead of smooth damping. It’s associated with dry-friction dampers and can make the ride feel inconsistent over small bumps.

Dry friction dampers slow suspension movement using friction between surfaces, rather than fluid flow. Because friction can vary with speed and load, they can be more prone to stick-slip and less smooth than hydraulic damping.

A steering damper adds resistance to steering movement to reduce unwanted oscillations, especially at speed. The transcript describes an older style where a knob adjusts damping through a friction pack near the steering pivot.

Suspension travel is the distance the suspension can move from its normal position to full compression or full extension. More travel generally lets the wheel absorb larger bumps without topping out or bottoming, which can improve speed and control in rough terrain.

The episode states that suspension energy absorption scales with the square of suspension travel. In practical terms, increasing travel doesn’t just add a little extra capability—it can dramatically increase how much bump energy the suspension can soak up before running out of stroke.

Suspension harshness is the unpleasant, jarring feel that happens when the suspension can’t move smoothly enough to keep the rider comfortable and the tire controlled. The transcript links it to a limit on how hard riders can push, even if they’re physically willing.

Extended travel means the suspension is designed to move farther up and down before it reaches its limits. That usually improves the ability to absorb bigger bumps without bottoming out, but it can also change how the bike feels as riders push toward the handling limits.

Spring rate is how stiff the suspension spring is—how much force it takes to compress it a given amount. The speaker’s point is that, despite more suspension travel, the effective stiffness ended up matching what riders previously had with much shorter travel.

This describes a development/testing approach: push a suspension setup progressively until it reaches its failure or instability point. The idea is that most setups feel good for a while, but the real engineering value comes from identifying what breaks first under harder use.

Compression damping is the resistance a suspension damper provides when the suspension compresses (moves inward under braking, bumps, or landing). The transcript contrasts it with a simplistic “hole through which oil was pumped,” emphasizing that damping behavior strongly affects how the bike responds to impacts.

“Limited area” refers to the small passage the damper fluid must squeeze through. Smaller or more restrictive passages increase resistance to flow, which changes the suspension’s damping curve and how it feels over bumps.

A progressive compression valve changes damping resistance as the shock rod velocity increases, rather than staying fixed. The transcript says this made resistance more nearly proportional to shock speed, improving control when the bike is moving quickly through compression events.

Shock rod velocity is how fast the damper’s piston rod moves during compression or rebound. Damping that responds to rod velocity can better match how real bumps and impacts load the suspension.

An upshift is a gear change to a higher gear ratio, typically to keep speed up while reducing engine RPM. The transcript uses it to explain how the improved suspension allowed the rider to stay on power through a banking section without timing the shift precisely.

The speaker references a specific racing location feature—Daytona’s infield banking at turn five—to illustrate how suspension tuning can affect real lap execution. It’s a concrete example of where the suspension behavior matters under speed and load.

Anti-dive is a front-suspension control strategy meant to reduce how much the fork compresses under braking. On motorcycles, braking weight transfer can make the front end “dive,” changing steering geometry and making the bike feel unstable. Anti-dive systems try to counter that dive so the rider can brake harder without the same geometry change.

Yamaha is used as the example of a manufacturer whose bikes could out-brake competitors without anti-dive. The episode’s explanation is that when the front end sinks under braking, it lowers the center of gravity and changes the leverage that would otherwise lift the rear wheel. That real-world advantage made anti-dive less necessary and it “disappeared” from street bikes.

Brake torque is the twisting force the brakes apply to slow the wheel, and “front brake torque” is that effect at the front wheel. The segment explains that as the bike’s center of gravity height and leverage change during braking, front brake torque can lift the rear wheel into a stoppie. In other words, it’s not just how hard you brake—it’s how the braking force interacts with suspension and geometry.

A stoppie is when a motorcycle’s rear wheel lifts off the ground during hard braking, effectively “standing the bike on its nose.” It happens because braking forces shift weight forward and the front suspension compresses, changing how the braking force creates lift at the rear. The episode ties anti-dive to reducing rear-wheel lift so braking can be more effective and stable.

A virtual pivot is an effective point in space that suspension linkages behave like they rotate around, even if there’s no physical joint there. In motorcycle/race-car suspension geometry, it helps explain how wheel motion relates to forces and how designers can target specific anti-squat/anti-wheelie behaviors.

A-arm geometry refers to suspension designs that use one or more control arms shaped like an “A” (or similar linkages) to locate the wheel. The arm angles and pivot locations strongly affect how the wheel moves relative to the chassis and how braking/acceleration forces create squat/dive or anti-squat/anti-dive effects.

Anti-squat is a rear-suspension behavior that reduces how much the rear end compresses under acceleration. By using linkage geometry, designers try to keep the tire contact patch more stable during hard throttle application.

Wheelies are when a motorcycle lifts its front wheel off the ground during hard acceleration. Suspension geometry can influence how easily weight transfer and rear suspension extension/compression allow the front to rise.

A Chebyshev linkage is a mechanical linkage arrangement that can produce a near-constant output motion over part of its travel, often used to transform motion types. In this context, the speaker ties it to using crossed twin swing arms to control how the rear wheel moves as the suspension cycles.

Chain tension is the load in the drive chain that pulls on the swingarm via the sprocket(s). On chain-driven motorcycles, changes in chain tension can create forces that affect swingarm movement and rear ride height.

Tangent force here refers to the component of the chain’s pull that acts in a way that tends to rotate or extend the swingarm. If the chain run isn’t aligned correctly, the chain can create an unwanted force that changes suspension position.

Chain slack is the amount of free play in the drive chain when it’s not under tension. Because chain slack changes how the chain loads the sprockets through suspension travel, some designs require careful setup to avoid binding or odd ride-height effects.

The Yamaha TZ500 is a classic Grand Prix racing motorcycle known for its two-stroke power and demanding setup. In this segment, it’s used as an example of a bike where rear chain slack adjustment is especially critical because suspension travel can create tight spots in the chain’s arc.

On a motorcycle, the drive chain doesn’t just transmit power—it also pulls on the rear sprocket. That pull changes how the rear suspension loads and therefore affects rear ride height under acceleration and braking.

Twist resistance is how well a chassis resists twisting under load. In suspension testing, measuring twist resistance helps quantify how stiff the frame is when forces try to rotate the rear assembly.

The Yamaha TZ 750 is a legendary racing motorcycle known for its powerful two-stroke engine and dominance in Grand Prix road racing. In this segment, it’s used as a real-world example of how rear suspension geometry responds during corner exit and throttle application.

An upstop is a mechanical limit that prevents the suspension from traveling upward beyond a safe range. When the bike hits the upstop, the suspension can no longer extend, which changes traction and handling behavior.

Center of mass is the point where the motorcycle’s weight effectively balances. The height of the center of mass affects how easily the bike can rotate under acceleration, which is why the segment discusses lifting the front wheel.

Winglets are small aerodynamic surfaces used to generate downforce or improve airflow. Here, they’re mentioned as a way to pull the front end down onto the pavement to counter front-wheel lift.

Wheeling is when a motorcycle lifts its front wheel off the ground during acceleration. The segment explains that aerodynamic downforce devices (like suction fans or winglets) or other strategies are used to keep the front tire planted.

The Honda NSR 500 is a Grand Prix racing motorcycle known for its 500cc-era four-cylinder design and for packaging fuel and exhaust in a way that protected the rider. In this segment, Honda’s 1984 NSR 500 is described with fuel carried under the engine and exhaust routing over the top, using an insulated “dummy tank” concept to manage heat and rider protection.

A slalom is a timed, cone-marked course that forces rapid left-right steering changes. It’s commonly used to evaluate handling and directional control, which is why it’s used here to compare two motorcycle configurations.

A MacPherson strut is a front suspension design where the shock absorber and the steering/suspension link are packaged together as one unit. It’s common in cars because it’s compact and relatively easy to package, but it can feel different from more exotic motorcycle front ends.

Directional stability is how well a vehicle resists unwanted yaw (side-to-side steering) and holds a predictable path. On motorcycles, poor directional stability can make the bike feel nervous or hard to control, especially at higher speeds.

A telescopic fork is the common motorcycle front suspension where sliding tubes (stanchions) move in and out to absorb bumps. In the segment, the host links it to how braking forces act on the fork, affecting whether the front end stays compliant over the road.

Side-loading means forces are applied to a component from the side rather than straight along its intended axis. For a telescopic fork under braking, side loads can increase friction/binding and reduce how well the front suspension can follow the road surface.

Hard braking is braking with enough force that the suspension compresses significantly and dynamic loads rise sharply. The segment uses it to explain how suspension geometry and loading can cause the front end to lose contact compliance with the pavement.

“Following the pavement surface” refers to the suspension’s ability to keep the tire in contact with the road as it moves over bumps and irregularities. If braking loads cause binding or reduced suspension travel, the tire can lose that ability, hurting grip and control.

Braking distance is the measured length required to slow a vehicle from a given speed to a stop. The host uses “shortest braking distances” as a performance outcome tied to suspension geometry, arguing that certain front suspension designs can improve how effectively the bike slows.

A pivoted front suspension is a front suspension layout where the wheel’s movement is controlled by linkages and pivots rather than purely sliding fork tubes. In the episode, the host connects this to braking performance, noting it can produce very short braking distances compared with other bikes.

A leading link suspension is a front suspension design where the fork links move the wheel in a mostly up-and-down path rather than the typical up-and-back motion of a telescopic fork. Because the wheelbase change is small, it can help keep steering geometry more consistent over bumps.

Wheelbase change refers to how the effective distance between the front and rear contact patches shifts as the suspension compresses or extends. Suspension designs like leading link aim to minimize this change so steering geometry stays more consistent over bumps.

A hub center front end is a motorcycle front suspension concept where the steering and suspension motion are organized around a central pivot near the wheel hub rather than a traditional fork tube. The goal is to reduce unwanted changes in geometry and improve control as the suspension moves.

The BMW Tazy is referenced as an early-1990s example of a motorcycle using a hub center front end. In this segment, it’s used to illustrate how designers tried to rethink the front end beyond conventional telescopic forks.