Slack Adjusters Air Brakes

The slack adjuster is the part of an air-brake system that is used to adjust the brakes when needed.

The slack adjuster is located on the air canister on the axle housing near the wheel.

On vehicles with drum brakes, it is between the pushrod and the S-cam.

On vehicles with disc brakes, it is between the pushrod and the power screw.

Air-brake systems use compressed air to transmit pressure from the brake pedal to the brake pads. Used in larger vehicles such as Diesel trucks es. Air-brake systems get out of adjustment over time.

Out-of-adjustment brakes are the most reportedproblem from roadside vehicle safety inspectors.

Out-of-adjustment brakes constitute a safety hazard, as vehicles with excessive brake slack can be difficult to stop.

All vehicles equipped manufactured since 1994 have automatic slack adjusters that adjust themselves during full brake applications.
Automatic adjusters should only require manual adjustment during installation.
If a brake system with automatic slack adjusters requires periodic adjustments, it is an indication that the automatic slack adjusters are defective and should be repaired.

All brake systems, whether they have automatic or manual slack adjusters, should receive regularly scheduled maintenance checkups.

Checking the manual slack adjusters on S-cam brakes.

Park on level ground. Chock the wheels to keep the vehicle from moving. Disengage the parking brakes so you can move the slack adjusters. Use gloves and pull hard on each accessible slack adjuster. If a slack adjuster moves more than about one inch where the push rod attaches to it, it probably needs adjustment. Adjust it or have it adjusted. Brake lining wear over time causes slack to develop in your brakes. Vehicles with too much brake slack can be very hard to stop. Out-of-adjustment brakes are the most common problem found in roadside inspections.
Be safe. Check the slack adjusters.

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