Comparing Single Serve and Free Backing Functions on a Demco Free Backing Brake Assembly

Question:

does the single servo and the free backing model hyd. brakes work the same when backing up?, And how well do they really release when backing up?, Thanks

asked by: Randy

Expert Reply:

Single serve refers to the wheel cylinder in a hydraulic drum brake assembly. It is an entirely separate component from the free backing option. A single serve, or uni-servo, wheel cylinder uses a single plunger to push the brake shoes against the drum.

When you are backing up, the wheel cylinder and the brake shoe springs work against each other. The dual spring and fall-away shoe design of the Demco free backing brakes allows the shoe to overcome the pressure from the wheel cylinder and the pressure is released from the drum.

Because of this, when you back up, you may feel the brakes grab slightly. This is expected and the brakes will release as long as everything is working properly.

expert reply by: John H