ASE A4 Suspension and SteeringWheel Alignment Diagnosis, Adjustment, and RepairMedium
A technician is performing a four-wheel alignment on a vehicle with an independent rear suspension. The alignment machine indicates a rear thrust angle of +0.3 degrees, with a specification of 0.0 degrees +/- 0.1 degrees. How should the technician proceed to correct this condition?
- AAdjust the front toe on the left side to compensate.
- BAdjust the rear toe on the right side to move the wheel rearward.
- CAdjust the rear toe on the right side to move the wheel forward.
- DAdjust the rear toe on the left side to move the wheel rearward.
Show answer & explanationAnswer & explanation
Correct answer: D. Adjust the rear toe on the left side to move the wheel rearward.
A positive thrust angle means the rear axle is pointing to the right of the vehicle's centerline. To correct this on an independent rear suspension, the left rear wheel needs to move rearward (or the right rear wheel needs to move forward) to bring the thrust line back to zero. Adjusting the left rear toe to move the wheel rearward will achieve this.
Why the other options are wrong
- A. Adjusting front toe does not correct rear thrust angle.
- B. Adjusting the right rear toe to move the wheel rearward would increase the positive thrust angle even further.
- C. Adjusting the right rear toe to move the wheel forward would increase the positive thrust angle.
Thrust Angle Adjustment
Thrust angle is the direction the rear wheels are pointing relative to the vehicle's centerline. It is adjusted by altering the toe of the rear wheels, especially on independent suspensions.
- Positive thrust angle: rear axle points to the right.
- Negative thrust angle: rear axle points to the left.
- Corrected by adjusting individual rear toe settings.
Memory trick: Thrust's a twist, correct the rear, make the centerline crystal clear.