Wheel Alignment Specifications & Adjustment Procedures: Description: Caster
Caster is forward or rearward tilt of steering knuckle in reference to position of upper and lower ball joints. Caster is measured in degrees of angle relative to a true vertical center line. This line is viewed from side of tire and wheel assembly. See Fig 1.
- Forward tilt (upper ball joint ahead of lower) results in a negative caster angle.
- Rearward tilt (upper ball joint trailing lower) results in a positive caster angle.
Although caster does not affect tire wear, a caster imbalance between 2 front wheels may cause vehicle to lead to side with least positive caster.