Automobile & Light Truck Certification Test A5 BrakesDrum Brake Diagnosis and RepairEasy
Which of the following is the PRIMARY function of the anchor pin in a drum brake assembly?
- ATo adjust the clearance between the shoes and the drum.
- BTo provide tension for the return springs.
- CTo serve as a fixed pivot point for the brake shoes.
- DTo secure the brake drum to the wheel hub.
Show answer & explanationAnswer & explanation
Correct answer: C. To serve as a fixed pivot point for the brake shoes.
The anchor pin is a stationary post on the backing plate at the top of the drum brake assembly. Its primary function is to provide a fixed pivot point against which the brake shoes expand when the wheel cylinder pushes them outward. This pivot point is crucial for the shoes to create the necessary friction against the drum.
Why the other options are wrong
- A. The automatic adjuster mechanism, typically a star wheel, is responsible for adjusting shoe-to-drum clearance.
- B. While return springs often connect to the anchor pin, this is a secondary function; its primary role is the pivot point.
- D. The brake drum is secured by the wheel studs and lug nuts, not the anchor pin.
Drum Brake Anchor Pin
A fixed post mounted on the backing plate of a drum brake system that provides a stationary pivot point for the top ends of the brake shoes.
- Crucial for proper shoe expansion and self-energization.
- Top ends of primary and secondary shoes rest against it.
- Ensures shoes remain centered and stable during braking.
Memory trick: The anchor pin, at the top, helps the shoes pivot and stop.