Caster is the tilting of the front steering axis either forward or rearward (3) from the vertical (1). Caster is measured in degrees. A rearward tilt is positive and a forward tilt is negative. Caster influences the directional control and the steering effort, but does not affect tire wear.

Caster is affected by the vehicle height. Keep the body of the vehicle at the deigned trim height. Overloading, weak or sagging springs will affect the caster angle. When the rear of the vehicle is lower than the designed trim height, the front suspension moves to a more positive caster angle. When the rear of the vehicle is higher than the designed trim height, the front suspension moves to a more negative caster angle.

Incorrect caster can be a result from damage to the control arms and other related front suspension parts. For trim height specifications refer to Trim Height in Suspension General Diagnosis.