The Slack Adjuster Wiki

What is a Slack Adjuster?

A Slack Adjuster is designed for use in S-Cam brakes which is mostly used in trailer and trucks, that is commercial vehicles. You can also call it an adjusting nut that is present on the back side of the brake drum and is used for brake adjustment.

How can you check if the Slack Adjuster is fitted properly?

To check if it is fitted as it should be, follow these steps:

* Park on a ground that is properly levelled.
* Then turn off the parking brakes and pull very hard on each slack adjuster.
* Observe and see if it moves more than one inch. If it does then slack adjuster is not fitted properly.

Why do we need it and why poor brake adjustment can lead to even death?

Believe it or not but most common cause of brake failure is poor brake adjustment. So when a slack reaches 1 inch (2.54 cm), the brakes must be adjusted. This is the most important inch of your life.

It shall be noted that when one brakes lightly, even poorly adjusted brakes seem to work. But under moderate to heavy braking especially in trucks doing heavy duty, you could find yourself in a runaway truck.

Adjusting Manual Adjusters

1. Turn the adjusting bolt until you feel solid resistance. Some adjusting bolts turn clockwise and some turn counter-clockwise. If you are turning the bolt the right way, the cam will turn in the same direction as it does when you apply the brakes. Watch the chamber push rod and slack adjuster arm. If you detect outward movement, you’re turning the bolt the wrong way.
2. Back off the bolt one quarter to 1/2 a turn to restore the clearance.
3. Now recheck push rod travel.