Today's Trucking
products Brakes Other


Posted: August 1, 2014 by Jim Park

Until recently, ‘failed brakes’ was simply another term for driver error. Industry experts figured a jackknife was a jackknife and most likely due to the operator making a mistake. Accident investigators would decide that if a truck didn’t stop in time to avoid a rear-end collision, the driver must have been following too closely.

That was then. These days, investigators have access to sophisticated post-accident testing equipment, and it’s becoming clear that failed brakes might really mean failed brakes. In one case, it seems there’s a serious design flaw–a direct result of an official American safety mandate, believe it or not–in so-called spring-brake-priority trailer air systems. In fact, one fatal accident in Toronto can be attributed in part to a documented case of trailer service-brake failure.

Hidden brake problems can be horrifying. At worst, these flaws can render your trailer brakes completely inoperative, but you would never know theyíre gone until the moment you need them. Which of course would be too late. Dale Holman is president of Truck Watch Services in Georgetown, Ont., and one of a handful of people in Canada using performance-based brake testers, or PBBTs. PBBTs are sophisticated diagnostic tools that measure braking force at each wheel. Holman confidently estimates that less than 20 per cent of the trucks on the road have brakes functioning as they were designed to. By a wide margin, most of the trucks he’s tested have failed, he says.

How should you react to that?

First, it’s important to remember that such flaws, or whatever you choose to call them, aren’t new. Problems with the function of some trailer-brake systems have plagued us for years. The thing is, there isn’t universal agreement on them. To say that brake systems on trucks and trailers are inherently flawed would be wrong. And the fact is, these problems aren’t too difficult to fix once they’ve been identified.

But detecting the gremlins might be the real issue. Most equipment for analyzing brake performance measures things like application pressure, timing, and actual brake force. It’s all critical stuff, but the industry has been repeatedly told by the enforcement community that brake stroke adjustment matters most. While the principle behind brake adjustment is valid, what if the slack adjusters are moving but little or no brake force is being applied to the wheel?

I’ve had a few moments of my own out there with trailers that wouldn’t stop. In one case, road sand was allowed to enter the brake chamber through the forward-facing pushrod opening and collect in a hard little pile against the front wall of the brake chamber. This effectively limited the travel of the piston within the chamber. The result was pushrods–six of them–that appeared to be in perfect adjustment, but the sand blocked the piston’s travel at the point where the linings made contact with the drum, producing almost zero brake force on three of the five axles. I had a few exciting moments with that trailer on Hwy. 17, north of Lake Superior.

The problem was a minor design flaw, but the mechanics looking after the vehicle couldn’t see past the fact that the slack adjusters were moving and the brakes appeared to be in perfect adjustment. I heard all the excuses, from hard linings to a problem in my tractor’s foot valve. It wasn’t until another driver stood so hard on the pedal that a pushrod bent and became jammed in the hole in the front of the chamber that they noticed the sand. In fairness to the mechanics, the problem wasn’t immediately obvious. But I complained as much as anyone else did, so surely they could have concluded the problem wasn’t on the power unit.

Recognizing the symptoms is an important first step in correcting the flaws. If you’re not comfortable with what you feel when applying the brakes, report the truck. Adjustment isn’t the be-all and end-all, and it may take a while to discover the real problem. But there’s no time like the present to get people listening.


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