NAPA Suspension and Steering 2 — Questions and Answers
Question 1: What is the primary purpose of positive caster on a front suspension?
- Compensating for road crown on rough roads
- Reducing tire wear on the inner edges
- Directional stability and steering wheel returnability (Correct answer)
- Increasing the vehicle's turning radius
Correct answer: Directional stability and steering wheel returnability
Positive caster places the tire contact patch behind the steering axis, which keeps the vehicle tracking straight and helps the steering wheel return to center.
Question 2: A vehicle pulls to the left, and the alignment readings show caster is uneven side to side. Which condition would cause this pull?
- More positive caster on the left wheel
- Equal toe-in on both front wheels
- Excessive negative camber on the right wheel
- Less positive caster on the left wheel (Correct answer)
Correct answer: Less positive caster on the left wheel
A vehicle tends to pull toward the side with the least positive caster.
Question 3: Feathered wear across the tread face of both front tires is most commonly caused by which alignment problem?
- Excessive positive caster
- Incorrect toe setting (Correct answer)
- Incorrect ride height at the rear
- Incorrect steering axis inclination
Correct answer: Incorrect toe setting
Too much toe-in or toe-out scrubs the tire sideways and leaves a feathered, saw-tooth wear pattern across the tread.
Question 4: Which alignment angle normally cannot be adjusted and is mainly used to diagnose bent suspension parts?
- Rear thrust angle
- Toe
- Steering axis inclination (SAI) (Correct answer)
- Camber
Correct answer: Steering axis inclination (SAI)
SAI is set by the suspension's design, so an out-of-spec reading points to bent parts such as a strut, spindle, or control arm.
Question 5: The included angle of a front wheel is equal to:
- SAI minus toe
- SAI plus camber (Correct answer)
- Caster plus camber
- Caster plus SAI
Correct answer: SAI plus camber
The included angle is the sum of steering axis inclination and camber, and comparing it side to side helps find a bent spindle or strut.
Question 6: During a four-wheel alignment on a vehicle with adjustable rear toe, which should be set first?
- Front caster, to establish directional stability
- Front camber, to correct tire wear
- Rear toe, to establish the thrust line (Correct answer)
- Front toe, to center the steering wheel
Correct answer: Rear toe, to establish the thrust line
Rear toe sets the thrust line, and the front wheels are then aligned to that thrust line.
Question 7: A turning radius (toe-out on turns) reading is out of specification on one side only. What is the most likely cause?
- Worn shock absorbers
- A weak rear coil spring
- Incorrect tire pressure
- A bent steering arm (Correct answer)
Correct answer: A bent steering arm
The geometry of the steering arm controls toe-out on turns, so a bent steering arm throws off the reading on that side.
