A vehicle exhibits a strong pull to the left and delayed steering wheel returnability after a suspension repair. The technician measures the front alignment angles and finds the following: Front Left Caster +1.0 degrees, Front Right Caster +3.0 degrees. Manufacturer's specification for caster is +2.5 degrees ±0.5 degrees. Which of the following is the MOST appropriate adjustment to correct the pull and returnability?
- ADecrease positive caster on the front left wheel.
- BIncrease positive caster on the front left wheel.
- CDecrease positive caster on the front right wheel.
- DIncrease positive caster on the front right wheel.
Show answer & explanationAnswer & explanation
Correct answer: B. Increase positive caster on the front left wheel.
A vehicle pulls to the side with less positive caster, and reduced positive caster also negatively impacts steering returnability. The front left wheel has significantly less positive caster (+1.0 degrees) than the right (+3.0 degrees) and is out of specification. Increasing the positive caster on the front left wheel will balance the caster and improve both the pull to the left and the delayed steering return.
Why the other options are wrong
- A. Decreasing positive caster on the front left would worsen the existing low caster condition and the pull to the left.
- C. Decreasing positive caster on the front right would worsen the caster split and the pull to the left, as well as negatively impact returnability.
- D. Increasing positive caster on the front right would further increase the caster split and worsen the pull to the left.
Caster Split Correction
Unequal caster (caster split) causes a vehicle to pull to the side with less positive caster. The remedy is to adjust the caster on the affected side(s) to bring them within specification and minimize the side-to-side difference.
- Unequal caster causes a pull.
- Pull is towards the side with less positive caster.
- Caster also affects steering returnability.
- Adjust to bring both sides within spec and reduce split.
Memory trick: Balance the caster, balance the pull.