Terminology
What is Ride Control | Vehicle Dynamics | Suspension System | Shock Absorbers | Struts | Terminology
A | B | C | D | E | F | G - H | I | J - L | M - O | P | R | S | T | U - Y
A
Aftermarket:A replacement part that is produced and sold by a company other than the original manufacturer.
Air Suspension:
A system in which air-filled, elastic springs are used in place of metallic springs.
Alignment Angles:
Camber, caster, toe, turning radius, and steering axis inclination. All these angles must be set correctly to ensure proper handling and tire wear.
Alignment:
The process of adjusting the position of the tires and steering axis to bring them to a specified predetermined position.
Axis:
A line or point marking the center of rotation of an object or thing.
Axle:
A cross support that is designed to carry the weight of the car.
B
Balance, Chassis:A ride condition that gives a level and flat front-to-rear flowing sensation without pitch.
Balance, Tire:
A condition in which the tire can spin without causing a vibration of the suspension or car.
Ball Joint:
A connector consisting of a ball and socket. This configuration allows for angular and rotating motion at the same time.
Bearing:
A device that allows rotation or linear motion with a minimum of friction. It usually uses a series of balls or rollers so there is a rotating motion of the internal parts.
Bellows:
A flexible, accordion-like seal used where angular or lateral motions require a large degree of movement.
Bottoming:
A noise and jolt created when the compression cycle of the suspension ends at the bump stops.
Bounce:
Straight-line motions of the sprung mass of a car in a vertical direction.
Bump Steer:
A directional change in steering caused by road surface irregularities. As the suspension moves through jounce and rebound, changes in alignment at the front or rear wheels may alter the vehicle's path.
Bump Stop:
An elastic member which increases the spring rate near the end of the compression and extension travel to reduce the effects of bottoming and/or topping.
Bushing:
A component made from a variety of natural and synthetic materials, used to locate or guide interconnected moving parts.
C
Camber:The inward or outward tilt of the wheel as measured in degrees. If a tire tilts inward toward the vehicle, it has negative camber. If the tire tilts outward away from the vehicle, it has positive camber.
Caster:
The amount, in degrees, that the steering axis is tilted from true vertical backward or forward viewed from the side of the vehicle.
Center Link:
A tube or rod used as a connection between the pitman arm and idler arm, and connected to the inner tie rod assemblies. Normally used on cars and light trucks.
Centrifugal Force:
A force acting on a turning body that pushes the body outward.
Chassis:
The portions of a car that remain after the body has been removed. It includes suspension and steering systems.
Center of Gravity, CG:
The balance point of a car.
Coefficient of Friction:
The amount of friction there is between two items that is dependent on the composition of the two materials.
Coil Spring:
A spring steel wire in the shape of a coil used as the springing medium for the suspension.
Compliance:
The ability to yield elastically to change position.
Computer Controlled Suspension:
A suspension system which uses a computer to change the shock absorber settings and/or air spring pressure to suit various driving conditions.
Control Arm:
A suspension member used to determine the position of a steering knuckle or axle, usually in a lateral direction.
Cornering Force:
The traction force in a lateral direction that is generated by a tire.
D
Damped, Dampened:A force or action opposing a vibrating motion to reduce the amount of vibration.
Deflection:
A movement that changes shape or position reacting to an outside force.
Directional Stability:
Ability of a car to travel in a straight line with a minimum of correction from the driver.
Dive:
A pitching motion of the sprung mass of a car downward at the front, which usually occurs during braking.
Drag Link:
A tube or rod used as connection between the pitman arm and steering knuckle. Normally used on cars and light trucks.
Dry Park Check:
An undercar inspection method performed with full vehicle weight on all tires. The steering wheel is turned left and right while the technician visually inspects the steering and suspension components.
Dynamic Balance:
A balancing of the lateral, centrifugal forces of a spinning tire and wheel.
E
Eccentric Cam:washers with a hole off-center so it does not rotate in a perfect circle. Normally used to adjust camber and/or caster.
F
Feather Edge:An abnormal tire wear condition in which each tire rib wears in a tapered, angled fashion.
Float:
A slow, low frequency movement of the car which produces a sensation of continuous front-to- rear, vertical movement of the suspension.
Force:
Physical power that will cause movement.
Frame:
The structural load carrying member that supports a car's engine and body, which in turn are supported by the suspension and wheels.
Frequency:
The speed at which an action occurs.
Full Contact Shims:
Shims used to correct alignment problems. Normally used on front-wheel drive vehicles with a straight rear axle.
G - H
G Force, g:A measurement of the amount of acceleration, braking, or cornering force that a car can generate.
Handling:
The relative ability of a vehicle to maneuver through turns and go where the driver wants it to go.
Harshness:
Vibrations that can be felt and/or heard that are caused by interaction between the tire and the road surface. It can be caused by tire or road irregularities.
Hop:
The vertical oscillations of a tire that can be caused by static or kinetic unbalance.
Hub:
The assembly that houses the bearings around which the wheel and tire assembly rotates.
I
Idler Arm:An arm and lever assembly used to support and maintain a parallel position with a conventional steering system.
Independent Front Suspension (IFS):
Suspension using two frame mounted control arms at each of the front wheels. Lets each wheel respond individually to bumps and dips in the road.
Inner Tie Rod Socket:
The pre-assembled unit that becomes the inner tie rod end. Used only on rack and pinion steering systems.
J - L
Jounce:A bounce motion during which the tire travels upward, relative to the car, compressing the spring and shock absorber.
King Bolt, KingPin:
A sturdy steel shaft used to connect the steering knuckle to an axle. It provides the pivot axis.
Lateral:
A direction that is to the side.
Linkage:
A system of levers and rods used to transmit motion or force.
Load Range:
A system of measuring and labeling the carrying capacity of the tires.
M - O
MacPherson Strut:See Strut.
OEM, Original Equipment Manufacturer:
The company that made the parts that were originally used on a car.
Oscillation:
A back-and-forth, repeating motion.
P
Pinion Housing:The portion of the rack and pinion unit that houses the spool valve and torsion bar.
Pitch:
Rotary motions of the sprung mass of a car around the transverse axis. The front end will rise while the rear lowers and vice versa.
Pitman Arm:
A steering component that provides interconnection between the steering gear sector shaft and the steering linkage.
Play:
Free movement of an item allowed by internal clearances.
Pressure:
A unit of force applied on a given area.
Pull:
A tendency for a car to steer toward one side.
A type of control arm that attaches to an axle at one end and pivots at the other end. It is often mounted in a lengthwise direction.
Rebound:
A bounce motion during which the tire travels downward relative to the car and the spring and shock absorber extend.
Returnability:
The tendency of the front wheels to return to a straight-ahead position.
Ride Control:
Achieving the objectives of the suspension while a vehicle is in motion.
Ride Height:
The distance from a specific point on a vehicle to level ground. The actual measurement should be equal to vehicle specifications before correcting alignment.
Road Shock:
A harsh force transmitted from the tires through the suspension or steering linkage.
Roll Rate:
The amount of resistance generated by the suspension components that resist roll.
Roll:
A rotary motion of the sprung mass of a car around the longitudinal (lengthwise) axis that results in body roll.
Roughness:
A heard or felt vibration generated by a rolling tire on a smooth road surface that produces the sensation of rolling on a course or irregular road surface.
S
Seal:A flexible rubber or synthetic material used to keep lubrication in and contaminants out of a specific area.
Shim:
A thin material, fiber or metallic spacer used to adjust the distance or angle of an item.
Shimmy:
A violent shake of the front wheels transmitted up to the steering wheel.
Shock Absorber:
A device, usually hydraulic, used to dampen or reduce the amount of spring oscillation after a bump.
Short/Long Arm (SLA):
An independent suspension design that incorporates unequal length control arms.
Skid:
A sliding rather than a rolling action of the tire across the road.
Solid Axle Suspension:
A suspension system consisting of one steel or aluminum 1-bearn extending the width of the vehicle.
Spring Rate:
The change of load on a spring per unit of deflection.
Spring:
A flexible suspension member, which allows bounce travel of the suspension.
Sprung Weight:
The total weight of the portions of the car, which are carried by the springs.
Squat:
A pitching motion of the sprung mass down ward at the rear that often occurs during acceleration.
Stability:
The tendency of a vehicle to maintain a directed course.
Steering Knuckle:
The front suspension component that attaches the front tire and wheel to the steering axis and steering linkage.
Steering System:
The entire mechanism that allows the driver to guide and direct a vehicle.
Strut Rod:
A suspension member that is used to brace the control arm to keep it from moving forward or backward.
Strut Suspension:
A suspension design in which spindle, shock, and spring are all one assembly.
Strut:
A suspension system type that utilizes the shock absorber as the upper tire position locating member.
Suspension:
An assembly used to support weight, absorb and dampen shock, and help maintain tire contact and proper wheel-to-chassis relationships.
T
Tie Rod Assemblies:The outermost assemblies on a parallelogram steering linkage. These assemblies are attached to the drag link and steering arms.
Tie Rod End:
The ball and socket assembly of a tie rod.
Tire Contact Area, Tire Print:
The amount of tire tread that is in contact with the road surface. Also called the "footprint."
Toe:
The difference in distance between the front and back of corresponding tires.
Toe In:
A condition where both tires of an axle are positioned so they are closer together at the front than the rear.
Toe Out:
A condition where both tires of an axis are positioned so they are closer together at the rear than the front.
Topping:
A noise and jolt when the extension cycle of the suspension travel ends at the bump stop.
Torque:
A twisting or turning force.
Torsion Bar:
A spring that allows suspension motion by twisting.
Torsion:
A rotating motion that causes a twisting action.
Track:
The center-to-center distance between the two tires on an axle.
Tracking:
The degree in which the rear tires follow behind the front tires.
Traction:
The ability of a tire to grip the road surface.
Transverse:
A direction that goes across a car.
Tread Width:
The outside-edge-to-outside-edge width of the two tires on an axle.
U-Y
Unsprung Weight:The weight of vehicle components not supported by the springs. Parts included are the wheels, tires, rear axle (but not always the differential), steering linkage, and some suspension parts.
Variable Rate Coil Springs:
Springs used to provide additional load bearing capacity for cars and light trucks. Unlike a standard coil spring, the coils of variable rate springs are not equally spaced. The bottom coils are more widely spaced than those at the top, which allows them to provide extra support when needed.
Vertical Movement:
The up-and-down movement of the ball joint or tie rod end.
Vibration:
A periodic motion or oscillation of an item that often causes an annoying motion or sound.
Wander, Weave:
The tendency of a car not to follow a straight line; it requires continuous correction from the driver.
Weight Transfer:
The amount of weight that moves laterally because of cornering forces or lengthwise, because of acceleration or braking forces.
Wheel Hop:
A rapid vertical oscillation of the tires resulting from a loss of traction control.
Wheelbase:
The center-to-center distance between the front and rear tires.
Yaw:
The rotary motion of the sprung mass of a car around a vertical axis that is encountered in a spin.