Wedge brakes are
- self operating.
- self lubricating.
- self adjusting. ✓
- self sealing.
Answer: C. self adjusting.
Wedge brakes are self adjusting.
Why this is the answer
The handbook's wedge brake section says these brakes are designed to adjust themselves. It explains that an air brake chamber pushrod slides a wedge between the brake shoes, pushing them outward against the drum. That description supports calling the wedge setup self-adjusting: the wedge action keeps the shoe position adjusted as it works.
Why the other answers are wrong
- A. self operating. — The passage describes the air brake chamber pushrod sliding the wedge; it does not say wedge brakes operate themselves.
- B. self lubricating. — No passage says wedge brakes lubricate themselves; it only describes their drum-and-shoe layout and wedge action.
- D. self sealing. — Nothing in the passages says wedge brakes seal themselves; the described action is forcing the shoes outward against the drum.
Remember it
Picture the wedge sliding between the shoes and keeping the setup adjusted as it works.
Official handbook: Official MTO Air Brake Handbook, Foundation Brakes – Wedge brakes