CDL Air Brakes TestInspecting Air Brake SystemsHard
A technician is performing a brake adjustment check on a Type 30 long stroke air brake chamber. The maximum allowable pushrod stroke for this chamber is 2.0 inches. If the technician measures a stroke of 2.25 inches, what is the correct action?
- AThe brake is within tolerance; no adjustment is needed.
- BThe brake is over-adjusted and needs to be loosened.
- CThe brake is out of adjustment and needs to be adjusted tighter.
- DThe brake chamber itself needs to be replaced immediately.
Show answer & explanationAnswer & explanation
Correct answer: C. The brake is out of adjustment and needs to be adjusted tighter.
A pushrod stroke of 2.25 inches exceeds the maximum allowable stroke of 2.0 inches for a Type 30 long stroke chamber. This indicates that the brake is 'out of adjustment' and has too much free play. The correct action is to adjust the slack adjuster to reduce the stroke to within the legal limit, which means adjusting it tighter.
Why the other options are wrong
- A. 2.25 inches is greater than 2.0 inches, so it is not within tolerance.
- B. Over-adjustment would result in a stroke that is too short, not too long. A long stroke means the brake is too loose.
- D. An out-of-adjustment brake does not automatically mean the chamber needs replacement; it first requires adjustment of the slack adjuster.
Brake Pushrod Stroke Limits
The brake pushrod stroke (distance the pushrod travels when brakes are applied) has maximum allowable limits for different brake chamber types. Exceeding this limit indicates an out-of-adjustment brake.
- Limits vary by chamber type (e.g., Type 30 long stroke: 2.0 inches).
- Longer stroke means brake is loose.
- Requires adjustment to tighten.
Memory trick: Long stroke, loose brake, adjust it tight, for safety's sake!