When should you adjust slack adjusters?

Jul 08, 2023

It’s a trick question. Today’s heavy-duty truck automatic slack adjusters should not need adjustment after they are properly installed at the time that the brakes are replaced. The more important question to ask is: When should you be inspecting heavy-duty truck slack adjusters? The answer is: Always. It’s a core component of a daily pre-trip inspection and should be looked at during regular preventative maintenance intervals.

“You maintain the brake adjuster during its operation with proper grease, proper maintenance, checking the function of the brake adjuster periodically, and especially during your daily inspections,” said Jeff Pond, program manager at Motor Wheel, who went on to confirm that “it’s recommended that you back them off or service them only when you’re installing new brakes.”

Heavy-duty slack adjusters, sometimes referred to as brake adjusters, are safety-critical components responsible for maintaining the optimal clearance between the brake shoe and drum, ensuring that the brake engages quickly without unnecessary dragging, especially during emergency stops or sudden braking events. If you do have a slack adjuster that’s out of spec, Pond noted that it could be an indication that something else is wrong with the braking system, such as worn linings or worn drums. You’d want to do a thorough inspection if the slack adjuster’s stroke is approaching two inches (or the specific legal limit for the brake chamber in question).

For more safety-critical insights from Pond, watch the video above.

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