What is a slack adjuster on brakes?

Slack adjusters are mechanical links between the brake-chamber push rod and the camshaft on cam type brakes. The entire slack adjuster operates as a unit, rotating with the brake camshaft as brakes are applied or released.

How does a automatic slack adjuster work?

When the brake is applied, a rod pushes out on the slack adjuster, which then turns the S-cam to force the brake shoes apart to apply the friction necessary to slow the truck. The automatic slack adjuster is designed to compensate for brake lining and drum wear to maintain a constant actuator stroke.

Where is slack adjuster used?

Slack adjusters are employed in S-camshaft drum brakes and take over the transfer of force from the wheel brake cylinder to the S-camshaft Thus, a manual or automatic adjustment of the S-camshaft is possible, so that the brake cylinder operates in virtually the same stroke range.

Are slack adjusters used to adjust brakes?

On an air-brake system, the slack adjuster is what is used to adjust the brakes. It is located on the axle housing on the air canister near the wheel. On drum brakes, it’s between the pushrod and the S-cam.

When should you adjust automatic slack adjusters?

Automatic slack adjusters are designed to continuously and automatically maintain the brakes in proper adjustment during normal use. However, they must be checked daily to ensure they are maintaining proper push rod travel – less than one in. (25.4 mm) when manually pulled and less than two in.

How do I know if I have automatic slack adjusters?

TSE Automatic Slack Adjusters (ASA) and Self- setting Automatic Slack adjusters (S-ASA) are identified by the part number which is marked on the cover plate. After a long life in service or while still on the vehicle, it can be difficult to read the information on the cover plate.

What’s the difference between manual and automatic slack adjusters?

Automatic slack adjusters perform the same function as the manual slack adjuster, except that it automatically adjusts for lining wear. It does not require periodic manual adjustment, however the slack adjuster does provide for manual adjustment if necessary.

How much play is allowed in a slack adjuster?

Use a tool such as a small pry bar to move the slack adjuster and check the brake’s free play – how far the center of the large clevis pin moves before the brake shoes come in contact with the drum. Free play should be between 3/8 and 5/8 of an inch.

How often should you replace slack adjusters?

approximately every 10,000 miles
Slack Adjuster Preventative Maintenance and Inspection At Wheelco, we suggest adjusting your manual slack adjuster approximately every 10,000 miles. However, this is just a general guideline since truck braking systems vary. When in doubt, call our service technicians for further assistance.

How do you remove a slack adjuster?

REMOVE SLACK ADJUSTER. Rotate the manual-adjusting bolt counterclockwise (or clockwise with ArvinMeritor products) to back off the slack adjuster so it separates from the clevis. Use an impact wrench, because this task will destroy the internal clutch mechanism found in most automatic slacks.

How do you adjust self adjusting slack adjusters?

Even self-adjusting slack adjusters need to be checked regularly. Grease the adjusters and the cam brackets to increase their service life. When measuring the push rod distance, try to keep each axle at the same measurement to keep each wheel’s stopping ability the same.

How do you adjust slack adjusters on air brake systems?

Reverse the slack adjuster one-quarter to one-half of a turn to put a little distance between the drum and the linings. Pressurize the system and apply the brakes using normal pressure. You should have no more than one-tenth of an inch between the brake linings and the drum, and there should be no more that 2 inches of travel in the push rod stroke.

How to adjust automatic slack adjuster?

Locate the adjustment bolt, which is located on the base of the slack adjuster. Often there is a sleeve around the bolt that needs to be pushed inward to access the bolt. By using a box end wrench, the sleeve can be pushed down with the wrench. During this motion, the wrench will slip over the bolt in one motion.

How can you check slack adjusters?

Park on level ground,turn off parking brakes,pull hard on each slack adjuster. It shouldn’t move more than one inch.

Park on level ground,turn off parking brake and press brake pedal.

Park on an incline and see if the vehicle rolls.