Caster

Caster is the angle between the steering axis and the vertical axis of a wheel when viewed from the side of a vehicle, affecting how a car handles and steers.

Positive caster (when the top of the steering axis tilts toward the rear of the car) improves straight-line stability and helps wheels return to center after turning. This is why race cars typically use positive caster settings—it provides better control at high speeds and improved feedback to the driver.

In motorsport, engineers adjust caster angles to fine-tune a car's handling characteristics for different tracks and conditions. More positive caster creates heavier steering but better stability, while less positive caster makes steering lighter but potentially less stable. NASCAR and oval track racers often use different caster settings on left and right wheels to optimize cornering.