R and M Diesel Truck Brake Service
Short drive from down town Little Rock, Arkansas
Close to I-30 and I-530.
An S-CAM brake with excessive shoe to drum clearance will engage too late.
While one which is too tight will engage too soon and may drag.
This drag will reduce mpg and result in premature brake shoe and/or drum wear.
It is critical for both safety and maximum fuel economy that S-CAM brakes be properly adjusted.
It is important to note that all S-CAM brakes on a given vehicle be adjusted properly to avoid undue lateral forces or improper rear to front synchronization.
Trailer brake adjustment on fifth wheel units is also important to synchronization and lateral force equalization.
Figure 2 illustrates a typical S-CAM brake. The adjusting nut allows the shoe to be positioned closer or farther from the brake drum.
Besides an improperly set slack adjuster, two other abnormalities may cause an S-CAM brake to drag.
1. A broken return spring or a return spring that has lost its tension will cause a brake shoe to drag.
2. Excessive corrosion or lack of proper lubrication of the shoe mount and shoe to backing plate may also cause an S-CAM shoe to drag.
Remember, a dragging shoe causes reduced mpg and premature shoe wear.