- Overview
- Manual Slack Adjusters (MSA)
- How slack adjusters work
- Product Catalogue
- Installation & Removal
- Replacement
- Failure Analysis
- Preventive Maintenance
- Automatic Slack Adjusters (ASA)
- Components of Slack Adjusters
Brake Adjustment Procedure
A. Manual Slack Adjuster
Brake adjusters with locking collar (positive lock type) - Jack up the vehicle. Thoroughly clean the adjusting hex and locking sleeve area. Position a wrench or socket over the adjusting hex and disengage the locking sleeve by depressing it. With the locking sleeve fully depressed, adjust the brakes while rotating the tire and wheel. Use the wrench or society to turn the adjusting hex until the shoes contact the drum. Then back off the adjusting hex until the tire and wheel turn freely. The actuator should be as short as possible without the brakes dragging.
If the vehicle cannot be jacked up, thoroughly clean up the adjusting hex and locking sleeve area. Position a wrench or socket over the adjusting hex and disengage the locking sleeve by depressing it. With the locking sleeve fully depressed, use the wrench or socket to turn the adjusting hex until it will go no further indicating that either the shoes have contacted the drum or the adjusting hex has been turned in the wrong direction. Pull on the brake adjuster to make sure it will not move. If there is movement, adjustment was made in the wrong direction and the adjusting hex must be turned in the opposite direction until it will go no further. After establishing solid shoe-to-drum contact, back off the adjusting hex 1⁄4 turn for worn linings and 1⁄2 turn when relining brakes. The actuator stroke should be as short as possible without brakes dragging. Measure the chamber power stroke at 80-90 psi as described in subsection "B", "Self-Adjusting Brake Adjuster Brake Adjustment Procedure", below. Take a free stoke measurement as outlined in the section entitled Failure Analysis. Ensure there is at least 3⁄8" of free stroke. Free stroke less than 3⁄8" can cause brake drag. If you can't maintain maximum legal stroke and the free stroke is less than 3⁄8", contact the brake manufacturer for foundation or brake geometry problems.
CAUTION When the manual brake adjuster brake adjustment is completed, the adjusting hex should be positioned so the locking sleeve engages it, thus locking it in place. If the locking sleeve does not engage the adjusting hex, the brake adjuster can back itself off.
Brake adjuster with lock screw ball Indent type lock mechanism-Back off (turn counter clockwise) the worm shaft lock screw (if applicable). Make the necessary adjustment by turning the adjusting hex as described in item number 1 of this section. Following brake adjustment, make certain that the lock ball or plunger engages the worm shaft indent. Without such engagement, the slack adjuster can back itself off.