Wedge brakes are
- self lubricating.
- self sealing.
- self operating.
- self adjusting. ✓
Answer: D. self adjusting.
Wedge brakes are self adjusting.
Why this is the answer
The handbook explains that a wedge brake uses a wedge-shaped pushrod to push the linings against the drum, and that most wedge brakes have internal automatic adjusters. It also says that if lining movement is too large, those automatic adjusters have failed, which shows that normal wedge brakes adjust themselves. The passage adds that drivers cannot easily check wedge brake adjustment and that adjustment and repairs belong to a qualified mechanic.
Why the other answers are wrong
- A. self lubricating. — Nothing in the passages says wedge brakes lubricate themselves; the handbook discusses air pressure, a wedge pushrod, rollers, linings, and automatic adjusters, not self-lubrication.
- B. self sealing. — The passages describe wedge brakes as using air pressure and a wedge pushrod, and they never describe any self-sealing function.
- C. self operating. — Wedge brakes are applied by air pressure through the wedge pushrod, not by operating themselves; the self-acting feature described is the internal automatic adjuster.
Remember it
Remember the wedge brake has an automatic adjuster inside: it adjusts itself, but a qualified mechanic handles repairs.