Steering axis inclination is the number of degrees that a line drawn through the steering knuckle pivots is inclined from the vertical, when viewed from the front of the vehicle. This, in combination with caster, is responsible for directional stability and self-centering of the steering. As the steering knuckle swings from lock to lock, the spindle generates an arc, the high point being the straight-ahead position of the wheel. Due to this arc, as the wheel turns, the front of the vehicle is raised. The weight of the vehicle acts against this lift and attempts to return the spindle to the high point of the arc, resulting in self-centering, when the steering wheel is released, and straight line stability.