CDL Help Logo

slack adjuster

The lever between pushrod and S-cam that takes up brake slack.

Automatic slack adjusters adjust themselves but still must be checked. If one moves more than about one inch when you pull hard on it, the brake needs adjusting. Brakes out of adjustment are what roadside inspectors find most often.

Also called: slack adjusters

Why it matters on the CDL test

Questions ask how to check slack adjusters, how much movement means they need adjusting, and whether automatic ones may be adjusted by hand.

Appears in 13 test questions

See 10 questions on the Air Brakes test

Example: With the wheels chocked and the parking brake off, you tug each slack adjuster to feel for free play.

In other languages

Español
ajustador de holgura
Русский
регулятор зазора (slack adjuster)
Українська
регулятор зазору

Related terms

Where it comes from

  • CDL manual, Section 5.3.2 Check Slack Adjusters on S-cam Brakes
  • CDL manual, Section 5.1.8 S-cam Brakes

Checked on

Download on theApp StoreDownload on theGoogle Play

4.9Unified rating across the App Store and Google Play · 6,500+ ratings

Store ratings as of Oct 15, 2026

Free practice tests on this site. All 2,500+ questions are in the app with a subscription.

All air brakes terms