CDL Air Brakes TestInspecting Air Brake SystemsMedium
A driver is performing a pre-trip inspection and observes that the brake pushrod on a service brake chamber moves more than 1 inch when the service brakes are applied. What does this excessive movement indicate?
- AThe brakes are out of adjustment and require immediate service.
- BThe low air warning device is faulty.
- CThe brake linings are too thick and need replacement.
- DThe air compressor is over-pressurizing the system.
Show answer & explanationAnswer & explanation
Correct answer: A. The brakes are out of adjustment and require immediate service.
Excessive pushrod travel (typically more than 1 inch or specified by manufacturer/DOT) indicates that the brakes are out of adjustment. This can lead to reduced braking efficiency and potential brake failure.
Why the other options are wrong
- B. A faulty low air warning device is unrelated to physical pushrod travel.
- C. Thick brake linings would reduce pushrod travel, not increase it.
- D. Over-pressurization might affect braking force but wouldn't directly cause excessive pushrod travel due to maladjustment.
Brake Pushrod Travel
The distance a brake pushrod moves when the service brakes are applied, indicating proper brake adjustment.
- Excessive travel (e.g., > 1 inch for Type 30 chamber) means brakes are out of adjustment.
- Insufficient travel can also be an issue (e.g., brakes dragging).
- Crucial part of pre-trip inspection for braking efficiency.
Memory trick: Pushrod too far? Adjustment's a jar!