CDL Air Brakes TestUsing Air BrakesMedium
When checking the slack adjusters on S-cam brakes, what is the maximum amount of free play or movement allowed at the pushrod when the brakes are NOT applied?
- A1/2 inch
- B1 inch
- C3/4 inch
- D2 inches
Show answer & explanationAnswer & explanation
Correct answer: B. 1 inch
Excessive free play in the slack adjusters indicates that the brakes are out of adjustment and will not apply properly. The maximum allowed free play is 1 inch.
Why the other options are wrong
- A. 1/2 inch is an acceptable amount of free play, not the maximum.
- C. 3/4 inch is an acceptable amount of free play, not the maximum.
- D. 2 inches is far too much free play and indicates a severe brake adjustment issue.
Slack Adjuster Free Play
The amount of movement in the pushrod of an S-cam air brake system when the brakes are not applied. Excessive free play indicates the brakes are out of adjustment.
- Checked during pre-trip inspection.
- Brakes must be off.
- Maximum 1 inch of free play allowed.
Memory trick: One Inch is the Limit for Slack Adjuster Twitch!