Home › CDL Practice Tests › Air Brakes Questions › Question 26
What is the role of the brake drum in an S-cam system?
- A.It stores compressed air at each wheel
- B.It pumps air back to the compressor
- C.It provides the rotating friction surface that the stationary shoes press against to slow the wheel
- D.It adjusts its own clearance automatically
Correct answer
C. It provides the rotating friction surface that the stationary shoes press against to slow the wheel
Why
The drum turns with the wheel while the shoes are anchored to the axle housing. When the shoes expand into the drum, friction converts motion into heat and the wheel slows.
Manual topic: Air Brakes - Air Brake System Components · From the Air Brakes practice bank (AB-026).