ASE A4 Suspension and SteeringWheel Alignment Diagnosis, Adjustment, and RepairMedium
A client complains of a vehicle pulling to the right. During a four-wheel alignment, the technician observes that the rear thrust angle is +0.8 degrees. The specification for thrust angle is 0.0 degrees +/- 0.2 degrees. The front alignment angles are all within specification. What is the most likely effect of this thrust angle on the vehicle's handling?
- AThe vehicle will exhibit excessive tire wear on the inner edges of the front tires.
- BThe vehicle will pull to the right.
- CThe vehicle will pull to the left.
- DThe steering wheel will be centered, but the vehicle will dog-track.
Show answer & explanationAnswer & explanation
Correct answer: B. The vehicle will pull to the right.
A positive thrust angle indicates that the rear axle is pointing to the right of the vehicle's centerline. To compensate for this, the driver must steer slightly to the right to keep the vehicle going straight, resulting in a pull to the right.
Why the other options are wrong
- A. Tire wear from thrust angle is typically uneven on the rear tires, and can cause feathering on the front tires from the constant steering input.
- C. A positive thrust angle typically causes a pull to the right.
- D. The vehicle will dog-track (move sideways) AND the steering wheel will be off-center (to the right) to compensate.
Thrust Angle Effects
Thrust angle is the direction the rear wheels are pointing relative to the vehicle's centerline. A non-zero thrust angle causes the vehicle to 'dog-track' and often leads to an off-center steering wheel and vehicle pull.
- Positive thrust angle: rear axle points right.
- Negative thrust angle: rear axle points left.
- Causes dog-tracking and a steering wheel offset.
Memory trick: Thrust to the right, pull to the right; thrust to the left, pull with all your might!