TORONTO, Ont. – Widespread installation problems involving brake drums could be placing trucks out of service even when fleets think their brakes are properly adjusted, an Ontario brake expert says.

The problem is with procedures involving outboard-mounted brake drums, says Dale Holman of Truck Watch Services. If the drum isn’t perfectly centred during installation, the brakes can appear in adjustment at one point, but fall half an inch out of adjustment after a partial rotation of the wheel, he says.

“We’re seeing this with, I’d say, 60 per cent of the outboard-mounted drums.”

The problem is similar to issues created when brake drums aren’t perfectly round – otherwise known as ovality.

Manufacturing tolerances simply aren’t tight enough to prevent the problems on their own, he adds. “And if the tolerances were too tight, we’d have to cut the drum right off when it has to be removed.”

“But are they the ones that deserve to get dinged?” Holman asks, referring to the equipment that’s found out-of-service by Ontario Ministry of Transportation inspectors. In fact, the issue may explain why a Commercial Vehicle Safety Alliance inspector can find brakes to be out of adjustment at one location, only minutes before a mechanic finds them to be properly adjusted during an inspection at another point within the same yard. The wheels are simply sitting in a different position within their rotation.

So too could the problem lead to premature wear for tires and ABS, as the components hammer back and forth, and drums can face problems related to the “super heating” of areas where brake contact is too tight, Holman adds.

The problem, however, can be addressed with simple mounting procedures, he says. Simply mount the brake drum, put the wheels on, tighten the two opposite fasteners to pull components into place, apply the brakes by either winding them in or applying the parking brake, back off the two nuts that you initially tightened, and then follow normal torque procedures for the wheel-end fasteners. But be aware that you might hear a loud bang when the two nuts are backed off, as components drop into position, Holman adds.

“We’ve cleared shops with that noise.” n