What is a slack adjuster and why is it important to your vehicle’s braking system? We get this question a lot at Wheelco. The slack adjuster is the component that is used to adjust the brakes using transfer of torque by converting convert linear motion into the rotary motion of the S-cam.
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. It is mounted on the S-cam shaft. One end is connected to the brake chambers’ pushrod. So, when the driver presses down on the brake pedal, air is forced into the brake chamber and shoves the push rod out. 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.
When the brake lining or brake pad wears, the gap between it and the brake drum increases. Automatic slack adjusters have an adjusting mechanism that adjusts for brake lining wear. However, manual slack adjuster periodically needs to be adjusted to properly function and operate at peak performance and compensate for lining wear. 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.
After 1994, all vehicles made have automatic slack adjusters installed. However, if you are driving a vehicle that predates this regulation, manual adjusters require fine-tuning. Read more about Brake FMSCA Regulations.
Be safe and check the slack adjuster movement. Often, improper adjustment is due to operator negligence. Should you require any additional information, contact Wheelco customer service to assist you.
Automatic Slack Adjusters operate in the same manner that manual slack adjuster does but with one key difference. They automatically adjust for the gradual brake lining wear. Therefore, it does not require periodic manual adjustment and is highly recommended not to adjust unless absolutely necessary or in an emergency situation.
Automatic slack adjusters are fast becoming a more reliable and consistent operational part, which is why Wheelco recommends using this type of slack adjusters. There are two types of slack adjusters: the stroke and clearance adjuster.
The stroke adjuster measures the stroke of the pushrod. It keeps the stroke constant, no matter if you brake hard or soft.
The clearance adjuster measures the clearance between the drum and brake lining and keeps the wear consistent (insufficient or excessive clearance between the brake lining and the drum). Once the lining meets the drum the adjusting mechanism disengages. This means that the brake adjusters’ automatic adjustment is not affected by the driver’s braking method (hard or soft).
Depending on your specific needs we offer several braking solutions.