Which of the following is an advantage of wedge brakes over S-cam drum brakes?
- Simpler design
- Installed on more commercial vehicles
- More braking power
- No exposed linkage ✓
Answer: D. No exposed linkage
The advantage of wedge brakes over S-cam drum brakes is that they have no exposed linkage.
Why this is the answer
The handbook describes the wedge brake as a pushrod and wedge working between two rollers inside the brake assembly, with the automatic adjusters built in. On the S-cam setup, the chamber pushrod works an outside slack adjuster that turns the camshaft. So on a wedge brake the operating parts are tucked inside rather than out where you can see them, which is the no-exposed-linkage advantage. The same passage notes a downside: you can't easily check wedge brake adjustment yourself, and adjustment and repairs belong to a qualified mechanic.
Why the other answers are wrong
- A. Simpler design — The handbook does not call wedge brakes simpler; it says their adjustment can't easily be checked by a driver and that adjustment and repair should be left to a qualified mechanic.
- B. Installed on more commercial vehicles — The handbook calls the S-cam system conventional and never says wedge brakes are installed on more commercial vehicles.
- C. More braking power — Nothing in the passages compares the braking force of wedge brakes and S-cam brakes, so more braking power is not supported.
Remember it
Picture the wedge and rollers sealed inside the brake assembly while the S-cam's slack adjuster and camshaft sit outside in plain view.