May 10, 2013
You’re driving on the interstate in a major city. There’s some open road in front of you, and a Class 8 unit creeping up in your rearview mirror. Both of you are moving at safe speeds, slightly below the posted speed limit, but traffic is heavy and other motorists aren’t as responsible.
Without warning, a car cuts in front you. No turn signal, no wave, just right past your front left fender and into your lane. If that’s not enough, as soon as they cut you off traffic stalls and they’re forced to slow down. You hit the brakes. You have to.
Through no fault of your own, you’ve made the brakes in the truck behind you the most important thing in your world.
If they work, you never notice them. The truck stops, the car in front of you speeds up again and you’re on your way.
But what if they don’t?
In situations like this, the importance of maintaining a truck’s braking system is obvious. For service facilities that perform braking system maintenance and repairs, scenarios like this are important reminders of what’s at stake every time they work on a vehicle.
The braking system doesn’t just stop the truck — it keeps all of us safe.
“I think there is a lot of awareness right now about braking systems, and the importance of maintaining those systems, and I think that awareness is growing,” says Tom Runels, engineering manager, drum brakes at Bendix Spicer Foundation Brake.
“Safety is so important,” adds Dennis Griffin, product manager for commercial vehicle friction at Federal-Mogul. “It’s common sense. If you are a driver, you have to be able to stop.”
The best way for fleets and owner-operators to keep their truck brakes safely working is to conduct regular brake inspections, checking the entire wheel-end system and its components for wear, faulty parts and early signs of breakdowns.
These inspections can be performed at any time and don’t take long, but like any type of preventive maintenance, they need to be done consistently.
Jim Baldwin, director of fleet sales at Marathon Brake, recommends brake inspections during every preventive maintenance interval.
For service providers who perform preventive maintenance, it is wise to create comprehensive brake inspection procedures technicians can follow.
The first step in conducting a brake inspection is positioning a tractor or trailer on a flat surface, such as a service bay. A tractor with a manual transmission should be put in neutral, and an automatic should be in park, says Scott Corbett, director, technical service and warranty at Haldex.
After the truck is positioned, make sure the air pressure in the braking system is near its OE-recommended level (approximately 120 psi). Corbett says that pressure will allow a tech to perform brake strokes during the inspection.
When the pressure is up, chock the wheels, shut down the vehicle and release the spring brake. Kevin Pfost, technical service, wheel end drum brakes at Bendix Spicer Foundation Brake, advises watching the air pressure levels for a few minutes after releasing the brake to make sure there is no leakage from the system.
He says Commercial Vehicle Safety Alliance (CVSA) regulations allow for a minor drop in pressure, but a precipitous drop due to a leak should immediately be repaired to avoid a violation. If the air system is good, a technician can begin manually checking each wheel end.
“You have to get under the vehicle and visually inspect everything,” says Corbett.
He advises checking the brake drums and linings first, as well as looking for obvious contamination affecting the system. Cracked drums should immediately be replaced, as should worn brake shoes that no longer have adequate friction material.
Some repairs will be necessitated by the end of a component’s useful life, per OEM recommendations. Griffin warns to study any components that need to be replaced before then, or due to uneven wear across a unit.
“Any unusual brake and wear patterns can be an indication of an issue that would need to be investigated further,” he says.
Adds Runels: “To just replace [a component] may not be the right thing to do. You have to find the root cause to really fix the problem.”
When components in one wheel end need to be replaced, OEs recommend also replacing the corresponding component on the other side of the vehicle.
According to a Meritor checklist, the visual inspection should continue with review of the S-Cam, slack adjusters, push rods and other components within the brake chamber. Make sure each component is tightened to OE specification. Handling each component is a simple way to find loose parts, says Pfost.
A brake application is needed for the next step of the inspection, Meritor says. With one technician positioned at the wheel end, a second tech engages a brake stroke from the cab. The technician under the vehicle is then responsible for measuring the length of the brake application within the chamber. CVSA regulations require a specific range for each brake chamber, so any stroke check that yields a number outside CVSA’s range should immediately cause concern.
This isn’t a measurement technicians should take lightly.
“When we say check, that doesn’t just mean a quick look,” says Mark Kromer, engineering manager, specialty products at Bendix Spicer Foundation Brake. “It’s a really clear [specification] and you have to check to make sure what you’re checking is within that value.”
And even if each wheel end comes in within CVSA regulations, that doesn’t mean the braking system is flawless. Slight variance from one wheel end to another can lead to uneven component wear and possible tire and alignment issues. Baldwin recommends further investigation in those situations.
Corbett advises techs to keep a small ruler in their pocket for brake adjuster length checks to get exact measurements. When wheel ends provide different measurements, Kromer says it is necessary to follow OE recommendations in resetting slack adjusters and system components.
He says automatic slack adjusters are exactly that, and technicians need to resist the urge to tighten them when measurements are off.
“If you [readjust them] on a regular basis, in effect you actually are wearing out the slack adjuster on an accelerated basis,” says Kromer.
Customers won’t be happy with that — especially in an age of heightened brake safety awareness.
Since CSA was released in late 2010, brake system maintenance has skyrocketed in importance. The standard P.M. brake inspection has never been more vital than it is right now.
“CSA changed the whole game,” says Corbett. “Now that the fleet has a scorecard and the driver has a scorecard they both take the hit. They realize they have to be more responsible.”
And while service providers don’t have CSA scorecards, you can bet customers keep track of how well you do when tasked with their brake inspections. Sometimes one error is all it takes to lose a customer forever.
Besides, think back to that opening scenario. Do you really want to risk it going the other way?
This is the first of a two-part series on brake inspections. The next installment, set to be published next week, will cover taking advantage of technologies available.