Jan `77
Brake Adjustments, Front vs Rear
On the CCE-IHC Dump Truck, the rear tandem, S-cam, foundation brakes require manual adjustment to the slack
adjusters, while the front axle wedge brakes have automatic adjusters built-in. With this set-up, commercial users report
the likelihood of brake unbalance of the foundation brakes unless the rear tandem is readjusted at relatively short mileage
or unless automatic rear slack adjusters are substituted on all tandem chambers. What happens is that the front brakes
keep automatically readjusting at short mileage as the front brake linings wear and the rear tandem does less and less
work as the tandem linings wear. Soon the front brakes end up doing most of the stopping of the truck. Also, front brake
lining wear is further accelerated with even shorter mileage between automatic readjustment cycles. Unbalance between
front and rear axles causes front axle lockups on slippery roads and gravel and could result in an accident. You're also
going to go through many sets of front linings.
It is very important to keep the front and rear brakes doing their portion of the stopping power for the truck, based on the
loaded front and rear axles weights. When loaded and after a few brake stops, cautiously feel the brake drums, all 6 of
them, and see if they are all about the same temperature. Also, watch for any front axle lockup or swerving tendencies.
Have a couple buddies check your rear tandem slack adjusters very often for correct angle settings. As you make a
gradual brake application from the cab, your buddies should observe that all 4 of the push-rods of the brake chambers
come out at about the same time, that they evenly push out at the same rate of speed, and that they all stop in the fully
applied position with the push-rod and the slack adjuster making a nice, 90 angle. This means that the rear tandem is
o
doing its share of the stopping job. If the push-rod over travels, so that the chamber side has an angle of less than 90 ,
then your front brakes are doing a lot of stopping work and the rear tandem is going along for the ride. Readjust the rear
tandem as soon as possible to insure safe, balanced brakes!
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