ASE A4 Suspension and SteeringWheels and Tires Diagnosis and RepairMedium
A customer complains of a rhythmic thumping noise that increases with vehicle speed. Upon inspection, you notice a distinct cupping or scalloping wear pattern on the outer edges of the front tires. Which of the following is the MOST likely cause of this tire wear?
- AWorn shock absorbers or struts
- BOverinflation
- CInsufficient toe-in
- DExcessive positive camber
Show answer & explanationAnswer & explanation
Correct answer: A. Worn shock absorbers or struts
Cupping or scalloping wear patterns are typically caused by a tire bouncing excessively due to worn suspension components, most commonly shock absorbers or struts, leading to uneven contact with the road.
Why the other options are wrong
- B. Overinflation typically causes wear in the center of the tread, not a cupping pattern.
- C. Insufficient toe-in (toe-out) typically causes feathering or scrubbing wear across the tread, not cupping.
- D. Excessive positive camber causes wear on the outer shoulder of the tire, not a cupping pattern.
Cupping/Scalloping Tire Wear
An uneven wear pattern characterized by alternating high and low spots around the tire's circumference, resembling cups or scallops.
- Often indicative of worn suspension components.
- Commonly caused by failing shock absorbers or struts.
- Results from the tire bouncing unevenly on the road surface.
Memory trick: Bad shocks make tires 'cup' their hands for help.