In a general passenger car, the front and rear wheel braking device is often not the same. If all four disc brakes, front disc brake ventilated multi-use, the rear disc brake plurality ordinary. If the disc is mixed with drum brakes, disc brakes front wheels, the rear drum brake employed.
disc brake:
also known disc brake disk brake, whichever shape suggests that it is named. It is controlled by a hydraulic pressure, the main components include a brake disc, cylinder, brake caliper, tubing and the like. Producing a steel brake disc fixed to a wheel and, with the rotation of the wheel. Cylinder fixed immovably on the bottom plate of the brake. Two friction plates respectively mounted on the caliper on both sides of the brake disc. Hydraulically acting piston cylinder tubing conveyed, pushing friction plate friction brake pressure to the brake disc occurs, the operation as if it clamped with pliers rotating plate, forcing it to stop the same. This brake heat dissipation, light weight, simple structure, easy to adjust. Especially when high load high temperature performance, braking effect is stable, but also not afraid of mud invasion, driving and poor road conditions in the winter, disc brake drum brake is easier to make than the car stopped in a short time.
In the conventional brake biggest difference disc brake disc ventilation, ventilation of the disc are hollow, more conducive to heat. The thermal stability of the brakes is very important, is related to the priority auto brake life and death. Because as the temperature increases, the braking force is decreased, the more powerful the higher the temperature drop, so that ventilation and cooling of the brake disk is advantageous.
drum brakes:
is the earliest form of drum brake auto brake, when the front disc brake has not yet appeared, it has been widely used in various types of vehicles . However, due to structural problems make it poor poor heat dissipation performance and drainage performance during braking, easily lead to decreased braking efficiency, thus nearly three years, in the automobile field has been gradually given way to exit the disc brake. However, due to relatively low cost, is still used in some cars in the economy class, mainly used for braking the rear wheel load is relatively small and the parking brake.
Usually a rear drum brakes. A typical drum brake mainly from the floor, the brake drum, brake shoe, the wheel cylinder (brake cylinder), a return spring, the positioning pin and other components groupto make. Plate mounted in a fixed position on the axle, which is stationary, with the above brake shoe, the wheel cylinder, a return spring, the positioning pin receiving rotational torque during braking. Each drum has a pair of brake shoes with friction linings on the brake shoes. The brake drum is mounted on the hub, the wheel is rotated together with the member, which is made of cast iron, a certain amount, the drum shaped like a garden. When the brake, the wheel cylinder compression piston pushes the brake drum brake shoes, drum brake deceleration by friction, forces the wheel to stop turning.
In addition to the cost of the drum brake is relatively low, there are an added benefit of parking (park) brake combination and together all of the rear drum brake cars, which is also the parking brake assembled on the rear wheel brake. This is a mechanical system, which hydraulic brake system of the vehicle completely separate: the use of a hand lever or the parking pedal tensioned steel cable (American car), drum brake actuating lever member of the brake shoe expansion, from to the parking braking action, so that the car does not slip movement; release steel cables, brake shoe return spring back into place, the braking force disappears.
Automotive designers from the economic and practical point of view, generally takes the form of mixed cars, front-wheel disc brake, rear drum brake. Four cars during braking, due to the inertia of the front wheel load percentage is usually 70 -80 percentage loading of all cars, so front wheel braking force larger than the rear wheel. Most cars nowadays we opened (e.g., leased, Beverly, Jetta), is not fully used in disc brakes, brake but Qianpanhougu mixed (i.e., using the front disc brakes, using the rear drum brake). As for the reasons for adopting non-ventilated disc rear wheel is also cost. After all, ventilated disc manufacturing process is much more complicated, the price is also relatively expensive. With the development of science and reduce material costs, in the automotive field, disc brake has gradually replaced the drum brake the trend.