What is the difference between disc brake and drum brake?



The so-called brake, in our life's words, is the brake to stop a moving car, and the brake is a part of the brake system used to create obstacles to the car's travel. At present, friction brakes are commonly used in automobiles

What is the difference between disc brake and drum brake?

The so-called brake, in our life's words, is the brake to stop a moving car, and the brake is a part of the brake system used to create obstacles to the car's travel. At present, friction brakes are commonly used in automobiles, that is, brakes that generate braking torque by friction between fixed parts and working surfaces of rotating parts. They are also divided into disc brakes and drum brakes.

For the drum brake, the internal tension drum brake is widely used in automobiles at present. The working surface of the brake drum of this brake is an internal cylindrical surface. The brake shoe is located inside the brake drum as a fixed part and the surface is equipped with a friction plate. When the brake shoe is stressed, one end will not move, and the other end will rotate around it, rotate outward, and press against the internal surface of the brake drum to generate braking torque. According to their different structures, drum brakes can be divided into leading and trailing shoe type, double leading shoe type and other different forms.

Disc brakes are generally divided into caliper disc brakes and full disc brakes. For caliper type, the rotating part is the brake disc and the fixed element is the brake caliper. It is worth mentioning that in the past, the caliper disc brake was only used as the central brake, but now more and more cars and trucks at all levels use it as the wheel brake, while the full disc brake is mainly used by heavy vehicles.

Why are more and more cars using caliper brakes?

It should not be said that cars, but almost all family cars have used the "disc" brake. It seems that it is difficult to find a family car that still uses the "drum" brake. Now it seems that only some low-end family cars still use the rear wheel drum brake, but it is relatively less and less! There are several reasons why drum brakes are less and less used in household cars!

1. Heat dissipation

As the whole brake system is wrapped by brake drum, the heat dissipation capacity of drum brake is much worse than that of disc brake! Generally, the drum brake of the truck is equipped with a spray system to reduce the temperature, so as to ensure that there is no thermal attenuation! In fact, generally driving in the city, due to traffic congestion and slow speed, there will be no heat failure! However, the serious heat failure often occurs on the long slope under the mountain running road, but there is no way. The concept that drum brake is easy to heat failure has taken root in consumer psychology!

2. Complex maintenance

I believe many friends have personally changed the brake pads, right? Even if you haven't changed the brake pads yourself, it's usually easier to change the disc brake pads. First break off the caliper, install the brake pads on top, and then push the piston inward! But the drum brake was very hard to pry off the brake drum. It took a lot of effort to get it off. As a result, I accidentally blew air. The brake dust was flying. After cleaning up the dust, I would face a lot of springs and reeds. If I didn't have the special tweezers, it would be too difficult to pull the spring down. It was a comparison with the alarm clock, and a lot of parts! After finishing all the work, we have to replace them one by one, especially the brake drum! After everything is done, the tension must be adjusted, otherwise the brake will be weak. In a word, drum brake maintenance is too troublesome!

3. Light disc brake

The lightening of cars is something that car enterprises all over the world are doing, and drum brakes with the same braking force are much heavier than disc brakes! The disc brake can further reduce the weight, for example, the brake disc made of cast aluminum and ceramic materials can further reduce the weight! Because of the positioning problem of the brake drum, which car enterprise will spare no effort to reduce its weight? If the weight is reduced and the cost is high, the competitiveness of some A0 cars will disappear! Therefore, the lightweight disc brake is also one of the important reasons why it can be popularized!

4. The brake force of drum brake is too large and not linear

Because of its structure, the drum brake has a greater braking force than the disc brake. High braking force is a good thing in itself, but too rapid and non-linear force is a disadvantage. For large trucks, the braking force may be the most important, but for domestic vehicles, a slight pedal on the brake can stop instantly and even lead to ABS intervention of the drum brake, which obviously makes you uncomfortable. In the past, drum brake is easy to lead to lock up when there is no ABS, But even with ABS, you can't let ABS intervene with a little effort? Right! The non-linear braking force makes it extremely difficult to accurately control ABS, ESP and other functions at the time of intervention! However, most of the drum brake family cars that can be seen on the market use the "front disc and rear drum", and the front and rear brake forces use a 7/3 braking force ratio. The brake mainly depends on the disc, and the rear drum only exists as an auxiliary. The rear drum can play its full role only after the front disc fails! The reason why the front wheel does not bulge is that its braking force is too fast and non-linear!

In a word, the above four points are the main reasons for the gradual disappearance of drum brakes in the field of household cars. Other reasons, such as ugly shape and fear of water, are also some, but the above four points are the main reasons after all. Drum brakes are prone to heat failure, complex maintenance, heavy weight and non-linear!