ASE A4 Suspension and SteeringWheel Alignment Diagnosis, Adjustment, and RepairMedium
A vehicle arrives with a complaint of poor steering wheel returnability after turns and a tendency to wander at high speeds. The alignment machine shows a front left caster of +0.5 degrees and a front right caster of +0.3 degrees. The manufacturer specification for caster is +2.0 degrees +/- 0.5 degrees. Which of the following is the most likely cause of the customer's complaint?
- AA significant caster split between the front wheels.
- BExcessive negative caster.
- CInsufficient positive caster.
- DExcessive positive caster.
Show answer & explanationAnswer & explanation
Correct answer: C. Insufficient positive caster.
Both front left (+0.5 degrees) and front right (+0.3 degrees) caster angles are significantly lower than the specified range of +2.0 degrees +/- 0.5 degrees (+1.5 to +2.5 degrees). Insufficient positive caster reduces the self-centering effect of the steering and can lead to wandering.
Why the other options are wrong
- A. While there is a small split (0.2 degrees), the primary issue is that both values are too low, not just the difference between them.
- B. The caster values are positive, not negative.
- D. The measured caster is far below the specification, not excessive.
Caster Effects
Caster angle influences steering stability, effort, and returnability. Positive caster provides directional stability and self-centering.
- Positive caster improves straight-line stability.
- Insufficient positive caster can cause wandering and poor returnability.
- Excessive positive caster can lead to heavy steering.
Memory trick: Caster's angle, steering's feel; too little, it wanders; just right, it's real.