A car’s braking mechanism is a device that is used to speed down the car. It’s always used to deal with exigence, such as preventing from knocking somebody or something, preventing from much bigger accidents and so on. It is made up of three parts: pedal, fluid drive system, brake shoes and brake drum. When we step on a pedal, the oil in the large cylinder is pressed and the pressure is transferred to the four small cylinders by tubes filled with oil, and then the pistons in the four small cylinders are pushed to expand the brake drum, so the brake shoes rub the inner side of the four wheels to speed down the car.