Automobile & Light Truck Certification Test A5 BrakesDisc Brake Diagnosis and RepairMedium
A technician is installing new brake pads on a vehicle with a single-piston floating caliper. After installing the pads and reassembling the caliper, they notice that the caliper is very tight against the rotor, making it difficult to rotate the wheel by hand. What is the most likely cause of this issue?
- AThe caliper guide pins are seized or corroded.
- BAn incorrect brake fluid type was used.
- CThe bleeder screw was left open.
- DThe brake pads were installed backward.
Show answer & explanationAnswer & explanation
Correct answer: A. The caliper guide pins are seized or corroded.
If the caliper is too tight against the rotor after pad replacement, and it's a floating caliper, the most common reason is that the caliper cannot slide freely on its guide pins. Seized or corroded guide pins prevent the caliper from centering properly over the rotor, causing it to bind and drag.
Why the other options are wrong
- B. Incorrect brake fluid type would cause seal degradation or improper system function over time, but not immediate caliper binding after pad installation.
- C. A left-open bleeder screw would cause a spongy pedal and no braking, not a tight caliper.
- D. Brake pads cannot typically be installed backward in a way that would cause this specific binding; they simply wouldn't fit correctly or wouldn't engage.
Caliper Binding After Pad Replacement
A tight caliper after new pad installation, especially on floating calipers, often indicates seized or corroded caliper guide pins preventing proper caliper movement.
- New pads are thicker, requiring more caliper movement.
- Guide pins allow the caliper to center itself.
- Lack of movement causes constant pad-to-rotor contact.
Memory trick: Tight caliper's a fright, guide pins not sliding right!