The disc brakes use a stationary brake disc to clamp the brake disc that rotates with the upper tire to generate friction and reduce the rotational speed of the wheel. When the brake pedal is depressed, the piston in the master cylinder is pushed and pressure builds up in the brake circuit. The pressure is transmitted to the piston of the brake cylinder on the brake caliper via the brake oil. After the piston of the brake cylinder is under pressure, it will move outward and push to force the piece to clamp the brake disc, so that the sheet and the brake disc are rubbed. In order to reduce the wheel speed, let the car slow down or stop.