Back to brakes

Oct. 7, 2008
“By far, brakes make up the largest percentage of out-of-service violations cited during the approximately three million roadside inspections conducted annually throughout North America. More attention must be paid to this problem.” -Stephen F. Campbell, ...

By far, brakes make up the largest percentage of out-of-service violations cited during the approximately three million roadside inspections conducted annually throughout North America. More attention must be paid to this problem.” -Stephen F. Campbell, executive director, Commercial Vehicle Safety Alliance (CVSA)

No matter how advanced we get with truck technology - be it emissions control, tracking devices, whatever - plain old brakes still remain the most crucial of components. Running loaded or empty, tractor-trailers, dump trucks, etc., all rely on brakes to maneuver and stop in normal and panic situations alike.

Even new safety advances - such as anti-rollover technology and stability control systems -- rely on good old basic brakes to get the job done.

The Commercial Vehicle Safety Alliance (CVSA) wrapped up its annual Brake Safety Week recently - conducting a variety of enforcement and educational activities nationwide to emphasize the importance of proper commercial vehicle brake inspection, maintenance and operation. Started in 2005 as part of its Operation Air Brake Campaign, their findings from Brake Safety Week won‘t be out for a while, but the trend lines so far are still worrisome.

For example, brakes still comprised the largest percentage - some 52.5% -- of out-of-service violations cited in roadside inspections conducted during CVSA‘s Roadcheck 2008 enforcements blitz, which takes a broader look at commercial vehicle and driver safety issues. One top of that, results from the Federal Motor Carrier Safety Administration‘s (FMCSA) recent Large Truck Crash Causation Study indicated that brake problems were present at the time of the crash in nearly one-third of all cases.

Finally, nearly 9% of all brakes on commercial trucks equipped with manual slack adjusters and 4% of all brakes equipped with automatic slack adjusters are placed out of service according to CVSA‘s data - proof that even technological safeguards aren‘t guarantees; that good maintenance practices are still vital where brakes are concerned.

“Commercial vehicle brake systems, vital to these vehicles' safe operation, are complicated and contain many parts, all of which need constant inspection and attention to ensure proper operation and performance,” noted Stephen F. Campbell, CVSA‘s executive director, during the groups Brake Safety Week campaign. “There is much evidence that points to brakes continuing to be a significant safety concern.”

The experts at Troy, MI-based component manufacturer ArvinMeritor put out a nice list of tips for commercial truck braking systems not long ago, so I‘d thought I‘d share that here in this space. While most of the following is probably very rudimentary for most fleets and owner-operators, brakes are still not only a major focus of safety enforcement efforts but also still a major source of violations - meaning the basics aren‘t getting attended to. This information also just applies to foundation or “drum” brakes, which are still far more commonly used that their air disc brethren.

AUTOMATIC SLACK ADJUSTERS (ASAs). Always troubleshoot brakes when the air chamber stroke exceeds the allowable limits. When you need to replace one automatic slack adjuster, replace all the ASAs on the same axle with components that meet the original spec. Mismatched brands can result in uneven brake wear, unbalanced braking and poor brake performance. Excessive push rod stroke may be an indication that a problem exists with the foundation brake, automatic slack adjuster, brake actuator or other system components. If excessive stroke occurs, it‘s recommended that you troubleshoot the problem, replace suspect components, and confirm correct brake operation before returning the vehicle to service. In the event that a manual adjustment must be made (although not a common practice), a service appointment and full foundation brake, automatic slack adjuster, and other system components inspection should be performed as soon as possible to help ensure the integrity of the overall brake system.

CAM BRAKES. When you service cam brakes, take time to replace all the springs, anchor pins, bushings and rollers. This includes replacing the cam brake return springs each time cam brakes are relined. The return springs are critical to the alignment, the accurate return of the brake away from the drum, and brake adjustment with the ASA. Inspect the entire brake structure for wear, cracks or other damage. Replace damaged parts with new rather than welding or repairing. Lubricate the cam brake assembly as required.

VALVES. When you replace the valves in your air brake system, the new valves should have the same crack pressure as those you‘re replacing. Why? Because replacing a valve with one that has a higher or lower crack pressure than the original valve can result in an unbalanced brake system and unacceptable lining and drum life.

REPLACEMENT LININGS. Replace the linings on all four brakes of a tandem axle or at minimum both brakes of a single axle at the same time. If you don't, you could experience brake balance problems. Plus, not replacing a unit's brake linings at the same time may contribute to uneven wear, reduced lining life, maintenance problems or drum-cracking.

DRUMS. In the brake drum market, there are two basic types: cast and composite. They differ in their abilities to absorb and dissipate heat. Using different weight, sizes or types of drums on the same axle could result in unbalanced braking and improper functioning of the automatic slack adjuster. The result will be poor brake performance due to uneven lining and drum wear.

CAM HEADS. All may look the same, but cam heads vary from one manufacturer to another. Some are engineered to provide constant lift while others promise constant torque. As with any brake component, use the proper replacement cam. Failure to do so can result in an unbalanced brake system and unacceptable lining and drum life.

CAM ROLLERS. Are they properly lubricated? The way to lubricate a cam roller is directly in the web roller pocket and not at the cam to roller contact area. If you do this correctly you'll avoid creating flat spots. These flat spots adversely affect the brake adjustment which may result in premature brake wear or reduced braking performance. The best time to change your cam rollers is when you reline. That will save you both time and money.

LONG-LIFE BRAKE KITS. Brake shoes, rollers, camshafts and shoe return springs for long life brakes are specifically designed as a system for optimum brake performance. These components depend on each other to provide brake performance truck operators can depend on. Using non-OEM spec level components for maintenance or to upgrade from standard to long-life brakes could result in unbalanced braking, poor brake performance or decreased lining life. Brakes work as a system. When an original part is replaced by a “will-fit” part, performance of the entire system may be compromised. A will-fit part may be less expensive to buy initially, but it could cost you more down the road in downtime or reduced performance. So don't take a chance with something as important as your brakes. Replace brake parts with OEM quality standard components.

Brakes are nothing to skimp on. I mean, in the tractor-trailer world, you need to stop 80,000 pounds going 65 mph on the highway. That‘s a situation where no one wants their brakes to do anything less than perform at their best.

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