How do brake pads retract?

Answer 1

Well to try and put it in simple terms. If you've ever seen a caliper off of a rotor in the process of changing brake pads, there is a piston (the cup that's pushes the inboard pad) squeezed inside the caliper. As you push the piston back into the caliper, the inside of the caliper between the caliper wall and the cup, is a square cut black rubber seal that seals the fluid inside the caliper. It also performs the act of retracting the piston after pressure release. When you step on the brake pedal, hydraulic force of brake fluid presses against the piston, which in turn presses the inboard pad to the rotor. The square cut seal tilts onto the edge of its square cut during the fluid force pressure action, then when the pedal is released and fliud pressure no longer exists behind the piston, the square cut seal returns to the flat side of the cut assisting with the retraction of the piston. Consiquently, the inboard pad (piston side of the caliper) is the only physical pad movement when sqeezing the rotor to stop the vehicle. The outboard pad is stationary, and act as the anchor pad. Therefore, the air gap between the pads and rotors a very minimal when pumped out to resting rotation.

On a safety side note: If you change your own brake pads.....After installing the pads, pump those brakes until a firm pedal is attained, or you will not have brakes when you go to move the vehicle for the first time. Hope this helps explain the question.