ASE A4 Suspension and SteeringWheel Alignment Diagnosis, Adjustment, and RepairHard
A technician is performing an alignment on a vehicle. The alignment machine displays a Steering Axis Inclination (SAI) of 12.0 degrees on the left front and 10.0 degrees on the right front. The specification for SAI is 11.0 +/- 0.5 degrees. What is the MOST likely cause of this discrepancy?
- AIncorrect camber on the right front wheel.
- BA bent spindle or strut on the right front.
- CExcessive positive caster on the left front wheel.
- DIncorrect toe setting on the left front wheel.
Show answer & explanationAnswer & explanation
Correct answer: B. A bent spindle or strut on the right front.
SAI is a non-adjustable angle set by the suspension design. A significant difference between left and right SAI (2.0 degrees in this case, where the right is outside the 11.0 +/- 0.5 spec) or one side being out of spec, often indicates damage to suspension components like a bent spindle, strut, or control arm, rather than a misadjustment.
Why the other options are wrong
- A. Camber is part of the included angle calculation, but an incorrect camber alone would not cause SAI to be out of spec by this much without other indications. SAI is primarily a factor of the steering knuckle and strut/spindle.
- C. Caster affects the fore/aft tilt of the steering axis but does not directly alter the SAI angle, which is the inward tilt.
- D. Toe is a horizontal angle and has no direct effect on the vertical or inward tilt of the steering axis (SAI).
Steering Axis Inclination (SAI) Discrepancy
A significant difference or out-of-spec reading for SAI between the left and right sides typically indicates bent or damaged suspension components.
- SAI is non-adjustable.
- Set by suspension design.
- Discrepancies point to component damage.
Memory trick: SAI is fixed; if it's broken, something is bent.