The caster is the tilting of the front steering axis (at the top) (1) either forward or backward from the vertical. A backward tilt is positive (+) and a forward tilt is negative (-). The caster influences directional control of the steering but does not affect the tire wear. The caster is affected by vehicle height. Ensure that you keep the body at the designed height. Overloading the vehicle, or a weak or sagging rear spring, affects the caster. When the rear of the vehicle is lower than the designed trim height, the front suspension moves to a more positive caster. If the rear of the vehicle is higher than the designated trim height, the front suspension moves to a less positive caster.