ASE A4 Suspension and SteeringWheel Alignment Diagnosis, Adjustment, and RepairEasy
A technician is performing an alignment on a vehicle and observes that the front left caster is +2.5 degrees and the front right caster is +3.5 degrees. The specification is +3.0 degrees +/- 0.5 degrees. How will this caster split likely affect the vehicle's handling?
- AThe vehicle will pull to the right.
- BThe tires will wear excessively on the outer shoulders.
- CThe steering will feel 'loose' and darty.
- DThe vehicle will pull to the left.
Show answer & explanationAnswer & explanation
Correct answer: D. The vehicle will pull to the left.
A vehicle tends to pull towards the side with less positive caster (or away from the side with more positive caster). In this case, the left front has +2.5 degrees and the right front has +3.5 degrees. Since the left side has less positive caster, the vehicle will pull to the left.
Why the other options are wrong
- A. A pull to the right would occur if the right side had less positive caster than the left.
- B. Excessive outer shoulder tire wear is usually caused by excessive toe-out or positive camber.
- C. 'Loose' or darty steering is typically associated with excessive toe-out or insufficient positive caster symmetrically.
Caster Split and Pull Direction
Caster split refers to an imbalance in caster angle between the front wheels. A vehicle will typically pull towards the side with the numerically lower (less positive) caster.
- Less positive caster on a side causes a pull to that side.
- Caster aids steering stability and returnability.
- Equal caster is crucial for straight-line tracking.
Memory trick: Caster's difference, pull's direction, less positive guides to its section.