STEERING AXIS INCLINATION
Steering axis inclination is the number of degrees that the spindle support centerline is tilted from the true vertical plane, as viewed from the front. It has a fixed relationship with camber and does not change, except in the event of damage to a spindle or ball joint. The angle is not adjustable, and damaged parts must be replaced.
Camber is expressed as the number of degrees that the top of the wheel is tilted outward or inward from the true vertical plane when viewed from the front. Inward tilt is negative camber and outward tilt is positive camber. Excessive camber causes premature tire wear; negative camber causes wear on the inside of the tire and positive camber causes the tire to wear on the outside edge.
Camber is adjusted by means of eccentrics at the inner end of the upper control arms. Camber cannot be accurately measured without professional equipment.
Caster is the backward or forward tilt from the vertical plane of the steering knuckle centerline at the top, measured in degrees. A steering knuckle centerline tilted backward has positive (+) caster, while one tilted forward has negative (-) caster. Positive caster produces greater directional stability and requires greater steering effort, since it increases the self-centering effect at the steering wheel.
Caster is adjusted by means of eccentrics at the inner end of the upper control arms. Caster cannot be measured accurately without professional equipment.
Toe-in is the amount, measured in inches, that the centerlines of the wheels are closer together at the front than at the rear. Toe-in must be checked after caster and camber have been adjusted, but it can be adjusted without disturbing the other two settings. You can make this adjustment without special equipment, if you make careful measurements. The adjustment is made at the tie rod sleeves. The wheels must be straight ahead.