ASE G1 Auto Maintenance and Light RepairSuspension and SteeringHard
During a wheel alignment, a technician finds that the vehicle's thrust angle is significantly out of specification. All other alignment angles (camber, caster, toe) appear to be within acceptable ranges. What is the most likely cause of an incorrect thrust angle?
- ADamaged power steering pump
- BUnequal tire pressure between front and rear wheels
- CBent rear axle or misaligned rear suspension components
- DWorn front control arm bushings
Show answer & explanationAnswer & explanation
Correct answer: C. Bent rear axle or misaligned rear suspension components
Thrust angle refers to the direction that the rear wheels are pointing relative to the vehicle's centerline. If the thrust angle is out of specification, it indicates that the rear axle or independent rear suspension components are not aligned correctly, often due to a bent axle housing, bent control arms, or shifted subframe. This causes the vehicle to 'dog-track' or pull.
Why the other options are wrong
- A. A damaged power steering pump affects steering assist, not the vehicle's thrust angle.
- B. Unequal tire pressure can cause a pull, but does not alter the geometric thrust angle of the rear axle.
- D. Worn front control arm bushings would primarily affect front alignment angles (camber, caster, toe), not the rear thrust angle directly.
Thrust Angle Causes
An incorrect thrust angle, which indicates the rear wheels are not parallel to the vehicle's centerline, is typically caused by a bent rear axle or misaligned rear suspension components.
- Rear wheels point off-center.
- Causes 'dog-tracking' and pull.
- Usually due to physical damage or wear.
Memory trick: Thrust's Off, Rear's Lost, Bent Axle's Cost.