![]() The shims on the outside of the slack adjuster next to the snap ring are for adjusting “end play,” which should be between. Add or remove washers (shims) between the slack and the end of the cam tube to ensure that it lines up directly with the center of the clevis. This will help keep dirt and contaminants out of the bushings and seals. Next up is checking slack adjuster alignment and “end play.” Put the slack adjuster back on, placing a washer between the adjuster and the cam tube, and another on the cam head. Nylon bushings generally suffice for line haul and highway applications. Cam bushings are a low-cost component that can make a huge difference in the long run.īronze bushings are recommended for severe-duty vehicles and heavy-wear brake situations, such as refuse vehicles. ![]() Bendix recommends keeping radial play below 0.010 of an inch by replacing cam bushings as needed. Keep in mind that even if the radial play is below maximum, the next brake servicing may be several hundred thousand miles down the road, and too much radial play leads to uneven brake shoe wear, as well as a loss of stopping power. If the radial play is 0.030 of an inch or more, the cam bushing or camshaft is worn and needs to be replaced. Remove the dial indicator from the inboard end of the cam and rotate it over to the cam head, then manually move the cam head up and down to measure the radial play. Brake Jobs: More Than FrictionĬheck the lining wear: If it’s time to do a brake job and replace the friction, it’s time to check the cam bushings and shims as well.Īfter removing the wheel and brake drums, disconnect the slack adjuster from the chamber clevis by removing the clevis pin. Grease purged at the cam head can drop into the brake drum, contaminating the drum and lining, and impacting brake performance. ![]() Grease purging at the opposite end of the cam tube, near the S-cam head, indicates a bad grease seal that must be replaced. Seals inside the cam tube are engineered to let excess grease out of the area, meaning new grease should be added until any dirty grease or condensation is visibly purged out of the end cam tube near the slack adjuster. Putting in less grease than is needed to fill all interior gaps can lead to condensation forming inside the brake components, which may cause rust and corrosion. When greasing brakes, it’s important to grease the brake to capacity. For both regulatory and brake performance reasons, all slack adjusters and air chambers on any given axle must be the same type and size. Refer to the manufacturer’s instructions and mechanism tests to determine whether the slack adjuster is properly adjusting the brake.”Īnother important note on brake chambers and slack adjusters: There are two common types of brake chambers – standard and long stroke – as well as two common sizes of slack adjusters (5.5 inch and 6 inch, as measured from the center of the cam shaft to the center of the clevis pin). Manually adjusting an ASA involves working against its internal back-off clutch, which can impact the life of the adjuster. “There are many factors that can cause an automatic slack adjuster to overstroke, but none will be remedied by a manual readjustment. “If the brake is out of adjustment, do not adjust the automatic slack adjuster – I can’t emphasize this enough,” Pfost said. “If the brake is out of adjustment, do not adjust the automatic slack adjuster – I can’t emphasize this enough." ![]()
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