Table of Contents
How does slack adjuster work?
The slack adjuster assembly transmits the braking torque to the S-cam and facilitates the adjustment of clearance between the brake lining (brake pad) and the brake drum. Once this happens, it rotates the slack adjuster which forces the brake shoes out. The brake shoes press against the brake drum, applying the brake.
Is it OK to manually adjust automatic slack adjusters?
An automatic slack adjuster (ASA) is a lever between the air brake chamber and the s-cam brake camshaft used to actuate brakes. “ASAs should not be manually adjusted to correct excess brake stroke, as doing so is a dangerous practice when a brake is only out of adjustment or over stroke limitations,” he says.
How much do you back off a slack adjuster?
This will cause the pushrod to pull part way out of the air cylinder. Measure the distance between the air cylinder and the chalk mark. If the measurement is at or less than 3/4 of an inch, it does not require adjustment. Anything over 3/4 of an inch means the slack adjuster should be adjusted.
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.
What are 2 Functions of slack adjusters?
Slack Adjuster
- To convert the forward linear motion of the push rod into rotary motion of the camshaft.
- To act as a lever, thus generating greater force;
- To provide a means of reducing the clearance between the brake shoes and the brake drum.
How often should you grease automatic slack adjusters?
Every six months or 50,000 miles, grease the slack adjuster using an approved grease. The adjusters have a grease fitting to allow lubrication during normal chassis servicing.
How often should you grease slack adjusters?
How long does a slack adjuster last?
What does it do? It adjusts and takes up the slack in the stroke as the friction surfaces wear away. In a “normal” U.S. highway environment a manual slack adjuster would probably need adjustment approximately every 10,000 miles.
How do I know if my slack adjusters are bad?
Usually brakes locking up is s-cam or s-cam bushings. That’s fairly easy to check, with no brake pressure put a pry bar on the slack adjuster. If there’s any significant movement up down or back and forth (some in and out is fine) then everything needs to come apart.
How do I adjust slack adjusters?
Locate the adjusting mechanism on the slack adjuster. It usually takes a 9/16 wrench to turn it. Tighten it all the way; you should see the S-cams move and the brake shoes tighten against the drum. Then, loosen it 1/2 turn and you should be good.
What is normal free travel for 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 can you check slack adjusters?
Measure the distance between the air cylinder and the chalk mark. If the measurement is at or less than 3/4 of an inch, it does not require adjustment. Anything over 3/4 of an inch means the slack adjuster should be adjusted. There is one pushrod for each brake assembly at each end of every axle so check each of them.
What are the slack adjusters?
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. On disc brakes, it is between the pushrod and the power screw.
What is slack adjuster?
Slack adjusters (also called brake adjusters or just “slacks”) regulate the distance that the air brake has to travel to apply friction to the wheel. This distance increases as use of the brake causes the friction material of the brake shoe to wear away.