Home › CDL Practice Tests › Air Brakes Questions › Question 164
What causes pushrod stroke to gradually increase in normal use?
- A.Air pressure slowly stretches the brake chamber shell
- B.The camshaft becomes shorter over time
- C.The governor raises cut-out pressure as miles build
- D.Brake lining and drum wear increase the clearance the shoes must travel before they contact the drum
Correct answer
D. Brake lining and drum wear increase the clearance the shoes must travel before they contact the drum
Why
Every stop wears a small amount of friction material, so the shoes sit farther from the drum when released. The pushrod must move farther to close that larger gap, which is exactly what adjustment compensates for.
Manual topic: Air Brakes - Slack Adjusters · From the Air Brakes practice bank (AB-164).