Air & Brakes
Brake adjustment and out-of-service limits
Automatic slack adjusters still need to be checked. Excess pushrod travel is one of the fastest ways to get placed out of service.
The answer
How to check
- Chock the wheels, release the brakes and build full air pressure.
- Mark the pushrod where it exits the chamber.
- Apply a full brake application and measure how far the pushrod moved.
- Compare with the limit for that chamber type and size — the limit is stamped or listed by chamber type, so use the chart, not a guess.
If it is out of adjustment
An automatic slack adjuster that is out of adjustment is telling you something is wrong — a seized camshaft, worn linings, a failed adjuster or a bad chamber. Manually adjusting it hides the fault and it will come right back.
Also inspect
- Lining thickness and any cracks that reach the edge.
- Drum condition, heat checking and cracks.
- Loose or missing hardware and worn camshaft bushings.