What a brake caliper actually does
A brake caliper is a clamp on the disc. Pedal pressure moves a piston. The pads pinch the rotor. A seal walks the piston back.
Foot goes down. The master cylinder shoves a column of brake fluid toward the corners. That pressure does not stop the car. It arrives at a clamp hung on the disc — the caliper. Iron or aluminum, one piston or four, the job is the same: pinch the rotor.
Fluid lands in a bore. A piston walks out. On a floater that one piston pushes the inboard pad, then the housing slides on the pins so the outboard pad comes in from the other side. A fixed caliper skips the slide — pistons on both sides of the disc, same pinch. Either way you are looking at a hydraulic hand, not a motor. A C-clamp in the bay is just putting that piston back so a thicker pad will fit.
The pads are the grab. A steel backplate, a slab of friction, two of them, one on each face of the rotor. That is what turns pedal travel into heat. The square-cut seal around the piston rolls as the piston goes out, then pulls it back a hair when you lift so the pad does not drag. A dying caliper sticks. A glazed pad just polishes. The rotor is the disc. The caliper is the clamp. The pads are the bite.
