With CVSA Brake Safety Week 2008 having recently finished, here are eight tips to help truck owners and maintenance professionals get the brake performance they expect:
1) AUTOMATIC SLACK ADJUSTERS: 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.
Automatic slack adjusters should not need to be manually adjusted in service to correct excessive push rod stroke. Excessive stroke may be an indication that a problem exists with the foundation brake, automatic slack adjuster, brake actuator or other system components.
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.
2) 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.
3) 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.
4) 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.
5) 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.
6) 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.
7) 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.
8) 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-fitter’s parts may be less expensive to buy initially, but they 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 parts.
ArvinMeritor is a global leader in the design, manufacture and distribution of complete braking systems. The supplier provides complete aftermarket cataloging and parts ordering, as well as comprehensive technical publications and service manuals/bulletins to support its customers.
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