Home › CDL Practice Tests › Air Brakes Questions › Question 143
Which crack or defect in a brake drum is a reason to take the vehicle out of service?
- A.A visible crack in the drum, especially one that goes through or is spreading
- B.Normal light surface checking that a mechanic has already judged within specification
- C.Dust on the backing plate
- D.A drum that is warm after normal driving
Correct answer
A. A visible crack in the drum, especially one that goes through or is spreading
Why
A through or spreading crack means the drum has lost structural strength and can break apart or lose braking surface under load. That is not a watch-and-drive defect, because failure can remove braking at that wheel without warning.
Manual topic: Air Brakes - Brake Inspection · From the Air Brakes practice bank (AB-143).