Brake Caliper: Description and Operation

Fig. 1 Single piston disc brake assembly cross sectional view:

Fig. 2 Delco-Moraine single piston disc brake with single mounting bolt:

This single piston sliding caliper assembly, Figs. 1 and 2, incorporates a one piece housing with the inboard side of the housing bored for the piston. A seal within the housing bore provides a hydraulic seal between the piston and housing wall.
A spring steel scraper (wear sensor) is incorporated on each inboard shoe. When shoe lining has worn to within .030 inch of the shoe, the sensor scrapes the rotor and emits an audible high frequency sound indicating that the linings should be replaced.
The caliper assembly slides on a mounting sleeve which is secured by a mounting bolt. Upon brake application fluid pressure against the piston forces the inboard shoe against the inboard side of the rotor. This action causes the caliper to slide until the outboard shoe comes in contact with the rotor.