Suspension Glossary

This glossary explains the suspension, steering and chassis terms that come up most often when you shop for coilovers, springs, lift kits, air suspension and alignment parts. Each entry covers what the term means, why it matters when choosing parts, and where to find related products or calculators on Lower HQ.

A

Ackermann

Ackermann is steering geometry that turns the inside front wheel more than the outside wheel, because the inside wheel follows a tighter circle in a turn. It reduces tire scrub at low speed and in parking lots. Drift and track builds often reduce Ackermann or run parallel steering so both front tires work at high steering angles, which is why many angle kits include revised knuckles or tie rod pickup points. See steering angle kits.

Air management

Air management is the control system for an air suspension setup: the compressor, air tank, valves, pressure or height sensors, and the controller or app you use to raise and lower the car. Simple systems use manual paddle valves, while height-based systems read sensors at each corner and return to saved presets. The management you pick affects how consistent ride height is and how much wiring and trunk space the install needs. See air suspension.

Air suspension

Air suspension replaces steel coil springs with flexible air springs, often called bags, that are filled and emptied by a compressor. Changing the pressure changes ride height, so the car can sit very low when parked and rise to clear driveways and speed bumps. The spring rate also rises with pressure, so ride feel changes with height. Kits usually pair air struts or bags with a shock and require air management. See air suspension.

Alignment

An alignment sets the angles of the wheels relative to the car and to each other, mainly camber, caster and toe. Any change to ride height, control arms, tie rods or coilovers shifts these angles, so a professional alignment is part of finishing almost every suspension install. Poor alignment causes uneven tire wear, pulling and vague steering. If the factory range cannot reach your target specs, adjustable arms or camber parts are needed. See camber kits and alignment parts.

Angle kit

An angle kit, or steering angle kit, increases how far the front wheels can turn, usually through modified knuckles, extended lower control arms and revised tie rods. It is used mostly for drifting, where extra steering lock lets the driver hold larger slip angles and recover from slides. A good kit also manages Ackermann and bump steer, and it usually requires a full alignment and sometimes new tie rods afterward. See steering angle kits.

B

Backspacing

Backspacing is the distance from the wheel's mounting face to its inner edge, measured in inches. It tells you how far the wheel reaches inward toward suspension parts, brake calipers and the frame. Backspacing is related to offset but also depends on wheel width, so two wheels with the same offset can have different backspacing. It is a common spec for trucks and lifted builds when checking clearance. Use the wheel offset calculator.

Ball joint

A ball joint is a ball-and-socket pivot that connects a control arm to the steering knuckle, letting the wheel move up and down and steer at the same time. Worn ball joints cause clunks, wandering and uneven tire wear, and they are a safety item. Lowered and lifted vehicles can push joints to the edge of their angle range, so extended or high-angle ball joints are sometimes needed. See ball joints.

Body lift

A body lift raises the body of a body-on-frame truck or SUV off the frame using spacers at the body mounts, typically one to three inches. It creates room for larger tires without changing suspension geometry, ride quality or ground clearance under the frame and axles. Because the suspension is untouched, it is often combined with a leveling or lift kit. Bumpers, steering shafts and wiring may need attention afterward. See lift kits and leveling kits.

Bump steer

Bump steer is when the front wheels change toe, and therefore steer themselves, as the suspension compresses or extends. It happens when the tie rod does not move on the same arc as the control arms, which becomes more common after lowering or lifting. You feel it as darting over bumps or the car moving around under braking. Bump steer kits and adjustable tie rod ends correct the tie rod angle. See tie rods and tie rod ends.

Bump stop

A bump stop is a rubber, foam or hydraulic stop that limits how far the suspension can compress and cushions the final part of travel. On lowered cars the stock bump stop may be hit constantly, giving a harsh ride, so shorter or trimmed stops are common. On off-road trucks, larger hydraulic bump stops absorb big hits without bottoming out. Bump stop length should match your ride height and travel. See bump stops.

Bushing

A bushing is a rubber, polyurethane or composite sleeve that sits where a suspension arm, sway bar or subframe mounts to the car. It isolates noise and vibration while letting the part pivot. As bushings age they crack and allow unwanted movement, which feels like vague steering or clunks. Replacing them restores precision, and stiffer materials reduce deflection further at the cost of more road noise. See bushings and mounts.

C

Camber

Camber is the inward or outward tilt of the top of the tire when viewed from the front. Negative camber means the top leans in toward the car, which helps the outside tire keep a flat contact patch while cornering. Too much negative camber wears the inside edge of the tire on the street. Lowering usually adds negative camber, so adjustable arms or camber plates are used to bring it back to spec. See camber kits and alignment parts.

Camber plate

A camber plate is an adjustable top mount for a strut or coilover that lets the top of the strut slide inward or outward to change camber. Many camber plates also allow caster adjustment and use a spherical bearing instead of rubber for sharper steering feel. They are popular on MacPherson strut cars, where factory camber adjustment is limited. Some coilovers include camber plates and others reuse a separate top mount. See camber plates.

Caster

Caster is the forward or backward tilt of the steering axis when viewed from the side. Positive caster, where the axis leans back at the top, improves straight-line stability and steering self-centering, and it adds negative camber to the outside wheel as you steer. More caster also makes steering heavier. Caster is set by control arm and strut top positions, so adjustable arms or plates are needed to change it. See control arms.

Coilover

A coilover is a shock absorber or strut with a coil spring mounted directly over it, usually with a threaded body that lets you adjust ride height. Many also offer adjustable damping and come with fitted spring rates and top mounts. Coilovers let you set height and stiffness together, which is why they are a common upgrade for street, track and drift cars. Check spring rates, damping range and mounts before buying. See coilovers.

Compression

Compression, also called bump, is the motion of the suspension moving upward as the wheel hits a bump or the car leans into a corner. Compression damping is the resistance a shock creates during that motion. Too much compression damping makes the ride harsh and can skip the tire over bumps, while too little lets the body roll and dive too quickly. Some shocks adjust compression separately from rebound. See shocks and struts.

Control arm

A control arm is a hinged link that connects the wheel hub or knuckle to the chassis and guides the wheel through its travel. Most cars have lower arms and many also have upper arms. Adjustable aftermarket control arms let you correct camber, caster or toe after lowering or lifting, and some use stiffer bushings or spherical bearings for more precise handling. See control arms.

Corner balancing

Corner balancing is setting the weight on each tire using four scales and adjusting the spring perches of height-adjustable coilovers. The goal is usually equal cross weights, meaning the left front plus right rear matches the right front plus left rear. A balanced car turns the same in left and right corners and brakes more evenly. It is done after installing coilovers and before the final alignment, with the driver's weight accounted for. See coilovers.

D

Damping

Damping is how a shock absorber resists motion and turns spring energy into heat so the car does not keep bouncing after a bump. It is split into compression and rebound and depends on how fast the shock shaft moves. Damping must suit the spring rate: stiff springs with weak damping feel bouncy, while soft springs with heavy damping feel harsh. Many coilovers offer click adjustment to fine-tune damping. See shocks and struts.

Digressive valving

Digressive valving is a shock valve design that produces relatively high damping force at low shaft speeds, then lets force rise more slowly at high shaft speeds. Low shaft speeds come from body roll and pitch, so the car feels controlled in corners and under braking. High shaft speeds come from sharp bumps, so the shock stays more compliant over potholes. This is common on performance street and track dampers. See coilovers.

Double wishbone

Double wishbone suspension uses an upper and a lower control arm, often A-shaped, to locate each wheel. Because the arms can be different lengths, engineers can make camber improve as the suspension compresses, which helps cornering grip. It is used on many sports cars and trucks. Upgrades often focus on adjustable upper arms for camber correction and on coilovers designed for the shock mounting points. See upper control arms.

Droop

Droop is how far the suspension can extend downward from ride height, such as when a wheel drops into a dip or the inside wheel unloads in a corner. Too little droop lets the inside tire lift, reducing traction and stability. Lowering the car on short coilover bodies, or adding too much spring preload, often reduces droop. Helper springs keep the main spring seated when the suspension is fully extended. See helper springs.

E

End link

An end link connects each end of the sway bar to the control arm or strut. When a car is lowered, stock end links can put the sway bar at a poor angle, reducing its effectiveness or causing binding. Adjustable end links let you set the correct length and remove preload from the bar with the car at ride height. Spherical or heim-joint end links also remove rubber flex. See sway bar end links.

F

Front splitter

A front splitter is a flat panel that extends forward from the bottom of the front bumper. At speed it creates higher pressure above the panel and lower pressure below it, adding front downforce and reducing lift. On a lowered car, splitter height and ground clearance matter, so ride height and aero should be planned together. Splitters come in materials from flexible polyurethane to carbon fiber. See body kits and aero.

H

Helper spring

On a coilover, a helper spring is a short, very soft spring stacked with the main spring. It fully compresses at ride height but keeps the main spring seated when the suspension extends, so nothing rattles at full droop. On trucks, the term also refers to add-on load support springs or air bags that help carry towing and hauling weight without sagging. See helper springs and load support.

L

Leveling kit

A leveling kit raises the front of a truck or SUV, usually one to three inches, to match the rear, which most trucks leave sitting higher from the factory for load carrying. Kits use strut spacers, torsion keys or longer coils. Leveling makes room for slightly larger tires and removes the nose-down look, but it can change CV axle angles and requires an alignment. See leveling kits.

Lift kit

A suspension lift kit raises the vehicle using longer springs, spacers, new shocks and often revised control arms or brackets. Lifts range from small two-inch kits to large builds that need drop brackets and new driveline parts. A lift adds ground clearance and room for bigger tires, but it raises the center of gravity and can change steering geometry. Match the kit to your tire size and intended use. See lift kits and leveling kits.

Linear spring

A linear spring has a constant spring rate, so each inch of compression takes the same added force. Coilover springs are almost always linear, which makes handling predictable and makes the car's balance easy to tune. The trade-off is that a rate stiff enough for good body control can feel firm over rough roads. Linear rates are listed in pounds per inch or kilograms per millimeter. Use the spring rate calculator.

Lowering springs

Lowering springs are shorter, usually stiffer replacements for factory coil springs that drop ride height, often one to two inches. They are a simple, budget-friendly way to lower a car and reduce body roll while keeping the stock shocks or struts. Because factory dampers were valved for softer springs, pairing lowering springs with matched performance shocks improves ride and lifespan. Drop is fixed, not adjustable. See lowering springs.

M

MacPherson strut

A MacPherson strut is a suspension layout where the strut itself serves as the upper locating member, with a single lower control arm at the bottom. It is compact and inexpensive, so it is used on the front of many cars. The trade-off is limited camber gain, so lowered strut cars often lose camber control and roll center height. Camber plates, adjustable arms and roll center adjusters help. See shocks and struts.

Monotube

A monotube shock has a single pressure tube, with a floating piston separating the oil from a high-pressure gas charge. The larger piston and better heat dissipation give consistent damping during hard driving and resist fade. Monotubes are common in performance coilovers and off-road shocks. They can be mounted upside down on many applications, but the single tube can be more vulnerable to dents. See shocks and struts.

Motion ratio

Motion ratio is how far the spring or shock moves compared to how far the wheel moves. If the spring compresses 0.7 inches when the wheel rises 1 inch, the motion ratio is 0.7. Because the ratio affects both leverage and travel, the wheel feels a rate equal to the spring rate times the motion ratio squared. Knowing it is essential when comparing spring rates across different cars. Use the spring rate calculator.

Multi-link

Multi-link suspension locates each wheel with three or more separate arms or links, often five, instead of two wishbones. Separate links let engineers tune camber, toe and anti-squat behavior more independently, giving good ride comfort and grip. Multi-link rear suspension is common on modern sports sedans and coupes. Lowering can change toe and camber, so adjustable toe arms and camber links are common upgrades. See control arms.

P

Pillowball mount

A pillowball mount is a strut or coilover top mount that uses a spherical bearing instead of a rubber isolator. It removes the flex of rubber, so steering and damping inputs reach the chassis directly, sharpening response. The trade-off is more noise and vibration in the cabin. Many pillowball mounts include camber and caster adjustment, which is useful on lowered and track cars. See strut mounts and top mounts.

Polyurethane bushing

A polyurethane bushing is a firmer alternative to a factory rubber bushing. It deflects less under load, so wheel alignment stays more consistent during cornering, braking and acceleration, and it resists oil and aging. The trade-off is more transmitted noise and vibration, and some designs need grease to prevent squeaks. Polyurethane is used in control arms, sway bar mounts, subframes and differential mounts. See control arm bushings.

Preload

Preload is the amount a spring is compressed when the suspension is fully extended. On a coilover, adding preload does not change the spring rate. On designs where the perch sets height, it raises the car, and in every case it reduces available droop. Small preload keeps springs seated, but large preload is often used as a shortcut for ride height and can hurt grip on bumpy roads. See coilovers.

Progressive spring

A progressive spring has a rate that increases as it compresses, usually through variable coil spacing or wire diameter. The softer initial rate gives a comfortable ride over small bumps, while the firmer rate later in travel resists bottoming and controls body roll. Many lowering springs use progressive rates for street comfort. They are less predictable at the limit than linear springs, which matters on track. See lowering springs.

R

Rebound

Rebound is the suspension extending back down after compressing, and rebound damping is the resistance the shock provides during that motion. It controls how quickly the spring pushes the wheel and body back. Too little rebound damping feels floaty and bouncy, while too much can keep the wheel from returning to the road quickly, called packing down. Rebound is the most common single adjustment on coilovers. See coilovers.

Ride height

Ride height is how high the car sits at rest, usually measured from the wheel center to the fender lip or from the ground to a chassis point. It affects looks, center of gravity, aero, wheel clearance and suspension geometry. Lowering too far reduces travel and can worsen camber, roll center and bump steer. Plan height together with wheel and tire fitment. Use the ride height and wheel fitment calculator.

Roll center

The roll center is the theoretical point the body rolls around in a corner, set by the suspension geometry at each axle. The distance between the center of gravity and the roll center determines how much leverage the body has to roll. Lowering many cars drops the roll center faster than the center of gravity, increasing body roll. Roll center adjusters or correction ball joints restore the geometry. See ball joints.

S

Scrub radius

Scrub radius is the distance at ground level between where the steering axis meets the road and the center of the tire contact patch. It affects steering effort, feedback and how much braking or bumps tug at the wheel. Lower offset wheels and wheel spacers push the tire outward, increasing scrub radius and making steering heavier and more sensitive to ruts. Check offset changes before buying wheels. Use the wheel offset calculator.

Shock absorber

A shock absorber, or damper, is a hydraulic cylinder that controls spring motion by forcing oil through valves. Unlike a strut, a conventional shock does not support the car's weight or locate the wheel. Worn shocks cause bouncing, nose dive under braking and longer stopping distances. When changing spring rates or ride height, choose shocks valved and sized for the new setup. See shocks and struts.

Spring rate

Spring rate is how much force it takes to compress a spring a given distance, listed in pounds per inch or kilograms per millimeter. A 500 lb/in spring needs 500 more pounds of force for each added inch of compression. Higher rates reduce body roll and dive but transmit more bumps. Choose rates based on vehicle weight, motion ratio and use, not on the number alone. Use the spring rate calculator.

Steering lock

Steering lock is the maximum angle the front wheels can turn from straight ahead. More lock reduces turning circle and, in drifting, lets the driver hold bigger angles and catch slides that would otherwise spin the car. Lock is limited by the rack, knuckles, control arms and tire clearance, so increasing it safely usually means an angle kit rather than just adjusting the steering stops. See steering angle kits.

Strut

A strut combines a damper with a structural housing that locates the wheel and carries the car's weight through the spring seat. Because the strut is part of the suspension geometry, it also affects camber and alignment. Replacing struts often means replacing or reusing top mounts and springs, and complete strut assemblies simplify the job. Coilover struts add adjustable height and damping. See shocks and struts.

Strut tower brace

A strut tower brace is a bar that connects the left and right strut towers, usually under the hood. It reduces the towers flexing toward each other under cornering loads, which keeps alignment more consistent and sharpens steering response. Braces are most effective on cars with MacPherson struts and older or open-top chassis. Check hood and engine bay clearance before ordering. See strut tower braces and chassis braces.

Sway bar

A sway bar, also called an anti-roll bar or stabilizer bar, is a torsion bar that links the left and right suspension. When the body rolls, the bar twists and resists, reducing lean without stiffening the ride over bumps that hit both wheels at once. Changing front or rear bar stiffness is a powerful way to tune understeer and oversteer. Adjustable bars offer several stiffness settings. See sway bars and end links.

T

Tie rod

A tie rod connects the steering rack to the steering knuckle and pushes or pulls the wheel to steer. Its length sets toe, which is adjusted during an alignment. Worn tie rod ends cause loose steering and uneven tire wear. Lowered, lifted and angle kit builds sometimes need longer, stronger or bump steer corrected tie rods to keep steering geometry correct. See tie rods and tie rod ends.

Toe

Toe is how much the front edges of the tires point toward or away from each other when viewed from above. Toe in, with the fronts pointing inward, adds straight-line stability, while toe out sharpens turn-in. Even small toe errors wear tires quickly. Lowering or lifting changes toe, especially at the rear of multi-link cars, so adjustable toe arms or tie rods may be needed. See camber kits and alignment parts.

Track bar

A track bar, or Panhard rod, locates a solid axle side to side under the vehicle. When a solid-axle truck or Jeep is lifted or lowered, the fixed-length bar pulls the axle off center and can cause wandering or death wobble. An adjustable track bar re-centers the axle and keeps the bar at a better angle. It is a common companion to lift kits. See track bars and Panhard rods.

Twin-tube

A twin-tube shock has an inner working cylinder surrounded by an outer reserve tube that holds extra oil and a low-pressure gas charge. This design is affordable, rides comfortably and is used on most factory cars and many entry-level coilovers. It can heat up and fade faster than a monotube under hard repeated use, but it is less sensitive to dents in the outer tube. See shocks and struts.

U

Unsprung weight

Unsprung weight is the mass not supported by the springs, such as wheels, tires, brakes, hubs and part of the control arms and shocks. Lower unsprung weight lets the tire follow bumps more closely, improving grip and ride, because the springs and shocks have less mass to control. Lighter wheels and tires are the most common way to reduce it. Heavy oversized wheels on lifted trucks add unsprung weight. See wheel bearings and hubs.

W

Wheel offset

Wheel offset is the distance in millimeters from the wheel's centerline to its mounting face. Positive offset puts the mounting face toward the outside of the wheel, pulling the wheel inward, while negative offset pushes it outward. Offset decides whether a wheel clears suspension parts and fenders, and it changes scrub radius and steering feel. Compare offsets before buying wheels or spacers. Use the wheel offset calculator.

Wheel rate

Wheel rate is the effective spring rate measured at the wheel rather than at the spring. It equals the spring rate multiplied by the motion ratio squared. For example, a 600 lb/in spring with a 0.7 motion ratio gives about 294 lb/in at the wheel. Wheel rate, not spring rate alone, is what lets you compare stiffness between different cars and suspension designs. Use the spring rate calculator.

FAQ

What is the difference between spring rate and wheel rate?

Spring rate is the stiffness of the spring itself, while wheel rate is the stiffness the tire actually feels. Because most springs sit inboard on a control arm, they move less than the wheel. Wheel rate equals spring rate times the motion ratio squared, so the same spring can feel very different on two cars with different suspension layouts.

Should I choose lowering springs or coilovers?

Lowering springs are a simpler, lower-cost way to drop a car a fixed amount while keeping stock or matched shocks. Coilovers cost more but let you adjust ride height and often damping, and they allow corner balancing. If you want to fine-tune height, track the car or change setups later, coilovers are usually the better fit.

Do I need an alignment after installing suspension parts?

Yes. Changing springs, coilovers, control arms, tie rods, lift kits or leveling kits changes camber, caster and toe. Driving on an incorrect alignment wears tires quickly and can make the car pull or feel unstable. Let new springs settle, then have a professional alignment done at your final ride height.

What is the difference between a leveling kit and a lift kit?

A leveling kit raises only the front of a truck so it sits even with the rear, usually by one to three inches. A lift kit raises both ends, often more, using new springs, shocks or arms. Leveling is simpler and suits slightly bigger tires, while a lift adds more clearance and room for larger tires.