Caster is the tilting of the uppermost point of the steering axis, either forward or backward from the vertical, when viewed from the side of the vehicle. A backward tilt at the top is positive (+) and a forward tilt is negative (-). Caster influences the directional control of the steering, but caster does not affect tire wear. One wheel with more positive caster than the other wheel causes that wheel to pull toward the center of the vehicle. The vehicle will move or lead toward that side with the least amount of positive caster.