Why do we use disc brakes at the front and drum brakes at the rear, in almost every vehicle?

The statement is no longer quite correct.10 or 20 years ago, however, this was actually the case, and in the case of low-powered vehicles, this is still common today.

First of all, I would like to point out that drum brakes are not as much worse than disc brakes as some laymen often think.There is already a reason why trucks still generally have drum brakes today.

Drum brakes have the advantage that they are self-reinforcing.This means that earlier, when the brakes in a car were still operated by rope hoists, drum brakes made it possible to keep the actuating forces low. The classic parking brake (handbrake) is still operated today by a cable pull.

Disc brakes have the advantage that they are better ventilated (cooling) also the service and maintenance (for example, the replacement of the brake pads) is easier.In addition, such a brake disc is slightly lighter than a corresponding drum.

But why the combination of disc brake at the front and the drum brake at the rear?Braking systems in passenger cars are designed in such a way that approximately 80% of the braking power is provided on the front axle and the remaining 20% at the rear. This is because when braking, the weight shifts to the front axle and can therefore brake the front axle much more than the rear axle. In addition, the rear axle should not block under any circumstances, as the side guide of the rear wheels then breaks off and the vehicle can break out uncontrollably. So the brakes on the rear axle were weaker anyway (ABS was not standard at the time).

In addition, the unequal distribution of the braking power means that the front brakes have much more wear than the rear brakes and therefore the brake pads have to be changed more often there (lighter maintenance was an argument for disc brakes).

For drum brakes at the rear, the service brake (i.e. via the brake pedal) works hydraulically, while the classic parking brake is still operated via cable pull.With a drum brake, this can be easily detached (a piston for the hydraulics on one side and an eccentric for the handbrake on the other side) while with pure disc brakes you then need a second brake pliers, which have a slightly more complex mechanism. force from the rope pull. Nowadays, it is increasingly also available via an electric actuator.

There is therefore also a mixed form in which the rear brake discs are shaped in such a way that there is a small brake drum in the middle, which is responsible for the function of the parking brake, while the service brake is hydraulically applied to the external brake disc. Acts.

Disc brakes, however, are regarded by many drivers as more modern, better, more powerful and, last but not least, visually more attractive and, in combination with expensive alloy rims, are intended to underline the sportiness of a car, which is why, for marketing reasons, the There is also a trend to install disc brakes at the rear.However, there is usually no technical need to provide disc brakes.

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