ASE A4 Suspension and SteeringWheel Alignment Diagnosis, Adjustment, and RepairMedium
A technician is performing a four-wheel alignment. The alignment machine displays a front left caster reading of +2.5 degrees and a front right caster reading of +3.5 degrees. The specification for caster is +2.0 to +3.0 degrees with a maximum cross-caster (split) of 0.5 degrees. What is the correct action the technician should take?
- AAdjust the right front caster to +3.0 degrees.
- BAdjust both front caster angles to bring them within specification and achieve a cross-caster within 0.5 degrees.
- CNo adjustment is necessary as both readings are within the overall specification range.
- DAdjust the left front caster to +3.0 degrees.
Show answer & explanationAnswer & explanation
Correct answer: B. Adjust both front caster angles to bring them within specification and achieve a cross-caster within 0.5 degrees.
Both caster readings are individually outside the specified range of +2.0 to +3.0 degrees, and the cross-caster (split) is 1.0 degree (+3.5 - +2.5), which exceeds the maximum allowed 0.5 degrees. Therefore, both caster angles need adjustment.
Why the other options are wrong
- A. Adjusting only the right front to +3.0 degrees would make the right within spec but the left would still be out, and the cross-caster would still be 0.5 degrees, hitting the limit but not ideal.
- C. This is incorrect; the right front caster is +3.5 degrees, which is outside the +2.0 to +3.0 degree range, and the cross-caster is 1.0 degree, exceeding the 0.5 degree maximum.
- D. Adjusting only the left front to +3.0 degrees would make the left within spec but the right would still be out, and the cross-caster would remain too high.
Caster Split (Cross-Caster)
The difference between the left and right caster angles. A small split is acceptable, but excessive split can cause a vehicle pull.
- Influences steering stability and returnability.
- Affects steering effort.
- Should be within manufacturer's specified tolerance (typically 0.5 - 1.0 degree).
Memory trick: Both the individual and the difference must be in the green.