Race Cars of Yesterday, inc.

Angle of attack

The angle the plane of a spoiler makes with the direction of air flow

Bottoming

When the suspension runs into bump stops at the end of its travel

Brake fade

A partial or complete loss of braking power caused by excess heat

Bump steer

Toe change caused by vertical suspension movement

Bump stop

Rubber stop that cushions suspension when car is at full bump

Camber thrust

Lean of tire caused by camber distorts tire tread which will exert a force tending to restore the tread to its original position

Camber

The angle the tire makes with a vertical plane inward or outward

Caster angle

The measurment of caster in degrees

Caster

The angle made by a line between the upper and lower steering pivots and a vertical reference line when viewing the car from the side

Center of gravity

The only point where a car would be balanced no matter what position the car is rotated

Centrifugal force

A car at a constant speed through a constant-radius corner is acted upon by a constant force acting away from the center of the turn

Co-efficient of friction

A number which indicates the difficulty in sliding one surface against another

Contact patches

That portion of a tire's tread that touches the pavement

Cornering Force

The grip of the tire on the pavement which resists sliding sideways when there is a side force on the wheel

Downforce

Downward aerodynamic force acting to increase vertical force

Drag

Aerodynamic forces act toward the rear and tends to slow the car

Drift

Driving technique which uses large slip angles to slide the car through the turn

Droop stops

Rubber stop that cushions suspension when car is at full droop

Front roll couple

That roll couple resisted by the front suspension

Full bump

The extreme position of the suspension against the bump stops at the end of its travel

Full droop

Full downward extension of the suspension

Grip

Equal to the side force divided by the vertical force of the tire

High-speed instability

When car steers itself off to one side as a result of an imbalance in the slip angles of the front tires

Inertia force

Action opposite to the force accelerating the car

Inertia

The resistance of an object to traveling in a curved path

Instantaneous center

The center around which the wheel appears to raotate when it has been tilted from the vertical due to a bump or suspension movement

Jacking effect

A tendency to lift the car when acted on by a cornering force

Lateral weight distribution

Percentage of weight on left/right wheels due to location of center of gravity

Lift

Upward aerodynamic force acting to decrease vertical force

Limit of Adhesion

Maximum cornering force at which driver senses the tire breaking loose

Macpherson strut

Suspension using a single control arm at bottom of wheel suspension and a vertical or near-vertical strut composed of shock absorber and coil spring

Minimum ground clearance

Ride height's lowest distance from frame to ground

Negative acceleration

Braking forces

Neutral steer

When car does not oversteer or understeer

Opposite lock cornering

Turning wheels in a direction opposite to the turn when rear of car spins out due to oversteer

Oversteer

The condition of higher slip angles in the rear of the car

Polar moment of inertia

The resistance of a car to turning and how quickly a car reacts to a turn of the steering wheel

Rake

When ride height is higher at the rear than at the front to increase downforce at higher speeds

Rear caster

The angle of tilt in the rear suspension upright off the vertical, veiwing the car along the centerline of the axle

Rear roll couple

That roll couple resisted by the rear suspension

Roll axis

An imaginary line between the front and rear roll centers

Roll center

The point in space about which the car body rotates during a turn

Roll steer

Toe change caused by body roll

Roll stiffness

Resistance of a suspension to body roll

Roll

When body of car leans toward the outside of the turn due to centrfugal force

Scrubbing off speed

Throwing the car hard into a turn generates large slip angles which are used to slow the car down

Self-centering force

When wheel is turned, the tire contact point is moved to the left or right of the direction of travel creating force which tends to return the wheel so it points in the direction of travel

Side Force

Force on tire created by turning of the wheel

Slip angle

Angle of travel due to distortion caused by cornering force makes the car follow a path at an angle to the direction the wheel is pointed.

Sprung weight

Weight of chassis and all parts mounted on the chassis

Stability

Describes the handling of a car traveling in a straight line

Stable car

If a car tends to hold a straight line without regard to wind gusts or changing road conditions

Static position

Position of the suspension with no body roll, pitch, or vertical motion on the suspension when the car is at rest

Steady-state cornering

When centrifugal force and cornering force are equal while negotiating a constant-radius corner at a steady speed

Suspension travel

Total movement of the suspension

Sway bar

Device used to increase the roll stiffness of the basic suspension

Toe-in

When the front of the tires are closer than the rear

Toe-out

When the front of the tires are farther apart than the rear

Toe

The angle of measurement of tires looking down on them from above

Torque steer

When a car steers in one direction or another when the throttle opening is changed

Total roll couple

Torque caused by centrifugal force about the roll axis equal to the centrifugal force on the sprung weight multiplied by the distance from the roll axis to the center of gravity of the sprung weight

Transient handling

How cars handle when entering or leaving a corner where both speed and radius are changing

Transistional cornering

Entering or leaving a corner where both speed and radius are changing

Un-stable

If the car changes direction without turning the wheel

Understeer

The condition of higher slip angles in the front of the car

Unsprung weight

Weight of tires, wheels, and suspension parts

Virtual swing arm

A not necessarily real swing arm that connects wheel to instantaneous center

Weight distribution

Percentage of weight on front/rear wheels due to location of center of gravity

Weight jacking

The adjustment of weight diagonally across the car

Weight transfer

Increase of vertical force on rear tires during acceleration or on front tires during deceleration

Wheelstand

When front tires leave ground when there is just enough weight on the front tires to equal the weight transfer during acceleration

Yaw

Movement caused by side to side aerodynamic force

Zero toe

When the wheels are in a parallel position

Race Cars of Yesterday, inc.

1831 26th Street North St. Petersburg, Florida 33713 (727)328-1936