Truck News

In recent conversations with brake experts from Bendix and Meritor, I posed the question: What’s the one thing you see in the field that drives you nuts? Both Chad Mitts of Meritor and Gary Ganaway at Bendix said the same thing: Too many operators still meddle with automatic slack adjusters. “I think the number one issue is education around automatic slack adjuster maintenance,” Chad said. “We see this still to this day. People think every time that a truck has to be touched, that they have to adjust the slack adjuster. That is absolutely the worst thing you can do.”

Gary agreed wholeheartedly. “One of the things we are really surprised by, is the belief in a lot of circles that brakes need to be adjusted every trip, or every day or at every PM,” he said. “That is absolutely not the case. As a matter of fact, if a fleet or driver finds they need to adjust the brake, it’s probably an indication that their automatic slack adjuster is worn out, and that happens fairly regularly. Slack adjusters have a finite life expectancy – they do not last the life of the vehicle.” Depending on application, slack adjusters will need to be replaced after four or five years of use, Gary added.

Chad had one more beef: People who put air disc brakes on a vehicle or trailer with the expectation they won’t have to worry about them. Disc brakes work well, but they’re not maintenance-free, he emphasized. Matt said disc brakes sometimes get treated much like unitized wheel-ends when they were first introduced. People slapped them on and forgot about them, which led to some maintenance issues and some misplaced dissatisfaction with the product. Check out the October issue for an in-depth feature on braking systems.

Truck News

Truck News is Canada's leading trucking newspaper - news and information for trucking companies, owner/operators, truck drivers and logistics professionals working in the Canadian trucking industry.

Have your say

We won't publish or share your data


  • I whole heartedly agree with Chad and Gary on both subjects. I taught techs for Navistar for many years and the general opinion was you need to adjust slacks all the time. Most techs don’t understand the working of ASA’s or how to correctly adjust them. Neither do drivers know how to make the ASA’s work

    As for disc brakes, I have preached maintenance on the units for years be it hydraulic or pneumatic. Techs perhaps don’t know correct maintenance and drivers feel it is a rip off. I often remind techs and drivers of the Fram filter add, “Pay me know or pay me later.” Later is very expensive.

    I drove a tractor/trailer for four and one-half years with Meritor auto slacks on the tractor and Bendix auto slacks on the trailer and had zero problems. Knowing how to maintain and make the slacks work was my secret.