Automobile & Light Truck Certification Test A5 BrakesDisc Brake Diagnosis and RepairEasy
A technician is inspecting a vehicle's disc brake system. They notice that the brake pads on one side of the caliper are significantly more worn than the pads on the other side. Which of the following is the most likely cause of this uneven pad wear?
- AA faulty master cylinder causing unequal pressure.
- BA seized caliper guide pin or piston.
- COver-torqued lug nuts on the wheel.
- DAir in the hydraulic system.
Show answer & explanationAnswer & explanation
Correct answer: B. A seized caliper guide pin or piston.
Uneven pad wear, especially side-to-side on the same caliper, strongly indicates a mechanical issue preventing proper movement. A seized caliper guide pin or piston will prevent one pad from engaging or retracting correctly, leading to one pad doing more work or dragging.
Why the other options are wrong
- A. A faulty master cylinder would typically affect braking on multiple wheels or the entire system, not just one side of a single caliper.
- C. Over-torqued lug nuts can cause rotor warpage or vibrations but are unlikely to directly cause uneven pad wear within a single caliper assembly.
- D. Air in the hydraulic system would generally lead to a spongy pedal and reduced braking efficiency overall, not specific uneven pad wear on one caliper.
Uneven Pad Wear Cause
Uneven wear between brake pads on the same caliper is often caused by mechanical issues preventing proper caliper or piston movement.
- Indicates a problem with caliper's ability to float or piston movement.
- Common culprits include seized guide pins or sticky pistons.
- Can lead to reduced braking efficiency and premature pad replacement.
Memory trick: Wear and tear tells the tale of the caliper's fail.