Adjuster / Parts for trucks

Slack adjuster is used exclusively in truck brake systems. This component is placed on the brake camshaft and serves to adjust its rotation angle and maintain the desired shoe to drum clearance. This component transmits force from the push rod of the air chamber to the wheel brake and ensures efficient braking.

Types of slack adjusters for commercial vehicles

Catalogues contain components which differ in the following parameters:

• Type of adjustment. There are automatic (self-adjusting) and mechanical components. The former feature high accuracy of adjusting the brake shoe to brake drum clearance. The latter last longer and are usually cheaper.
• The number of working teeth. It may be 10, 19, 28, 37, etc.
• Place of installation. Right and left, front and rear slack adjusters are made for trucks. On each axle, two components are placed.

Malfunctions and their causes

Manufacturers do not state a specific service life for these devices. In case of regular maintenance with lubrication of the components, they can remain operable for a long time. Operability of the slack adjuster is determined by the stroke of the air chamber push rod: it should not exceed 40 mm.

This component is non-dismountable and is not subject to repair. A faulty component is to be replaced. This includes wear out of the bushing hole and splines in the gear. In addition, elements of the worm gear may get damaged: jamming occurs, defects of faces for the wrench, plugs loosen. The reason for a breakdown may be excessive load during operation, failure to comply with maintenance requirements, ingress of moisture and dirt into the unit.

How to detect failures

The components require regular inspection, in particular, measuring the push rod stroke. Such inspection is performed by feeding air into the brake chamber at the pressure of about 6.5 atmospheres. If the lever is OK, the clevis attached to the air chamber will fully return to its original position when brakes are released.

A faulty component may be identified by malfunctions in the system. If pressing the brake pedal requires considerable effort, and the truck doesn't stop for a long time, urgent diagnostics is required. Components should be replaced in pairs per axle to avoid uneven braking.

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