A technician is replacing brake pads on a vehicle with a single-piston floating caliper. After removing the old pads, they notice that the inner brake pad is significantly thicker than the outer brake pad. All other brake components appear to be in good condition. What is the MOST likely cause for this uneven wear?
- AA seized caliper piston.
- BA collapsed brake hose.
- CExcessive rotor runout.
- DA seized caliper guide pin on the inner side.
Show answer & explanationAnswer & explanation
Correct answer: A. A seized caliper piston.
In a single-piston floating caliper, the piston pushes the inner pad against the rotor, and then the caliper slides on its guide pins, pulling the outer pad into contact. If the inner pad is significantly thicker, it means it's not being pushed against the rotor as effectively as the outer pad. This is a classic symptom of a seized or sticking caliper piston, preventing it from extending fully and applying proper pressure to the inner pad.
Why the other options are wrong
- B. A collapsed brake hose would restrict fluid flow, potentially causing less overall braking force but not typically one pad being significantly thicker than the other in this specific way.
- C. Excessive rotor runout primarily causes pulsation and can lead to uneven wear across both pads, but not typically one pad being significantly thicker than the other in a floating caliper.
- D. Seized caliper guide pins would cause the caliper to bind, leading to the outer pad being thicker (less worn) because the caliper can't pull it into contact effectively, or the inner pad being excessively worn from constant contact, not thicker.
Floating Caliper Piston Seize
When a single-piston floating caliper's piston seizes, it fails to extend properly, causing the inner brake pad to wear less (remain thicker) than the outer pad, as the inner pad doesn't apply sufficient pressure to the rotor.
- Piston pushes inner pad.
- Caliper slides to engage outer pad.
- Seized piston means inner pad wears less.
Memory trick: Floating caliper, one pad thick, piston or pins, find the trick.