Cars

Thanks to Continental, the drum brake could become important again

The drum brake for the front wheels comes back. Suppliers Continental would like to show with a test vehicle that the old technology even in modern cars Can make sense. The tried and tested technology should again become a real alternative to disc brakes, especially for electric cars. For more than 50 years, drum brakes on the front axle have not been an issue in vehicle development, only on the Rear axle and in smaller vehicle segments the drums still play a role today. AUTO BILD explains the technical approach, shows the potential of the technology and has already driven the prototype.

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Drum brakes don’t have the very best reputation. they are sensitive to heat and often more complex to maintain compared to disc brakes. In addition, they are sensitive to so-called Fluctuations in the coefficient of friction react, which up until the 1970s led to a lack of directional stability and / or the rear of vehicles breaking away. Reasons why drum brakes are no longer used on the front axle these days. Even so, they offer some advantages that electric cars in particular can benefit from. Due to the high recuperation performance of new e-cars, the brakes are rarely used in many everyday situations. What at first sounds like more longevity of the brake pads and brake discs leads to the exact opposite with disc brakes. Due to the infrequent use, the discs easily rust, which can lead to reduced braking performance. With regard to the reduction of fine dust, the drum brake has the decisive advantage over disc brakes that it is self-contained. Most of the brake dust therefore remains in the brake drum and does not spread around the area.

Continental PP drum brake

The extremely large brake does its job well in the prototype.

This is how the drum brake works

But does this approach also work in practice? AUTO BILD has already been able to test it on a Continental test track at the Frankfurt am Main plant. as A Golf 7 GTI was used for the test car, whose disc brakes on all four wheels against Duo servo drum brakes have been replaced. Otherwise the system has not been greatly adapted to the new type of brakes. The first step on the pedal is therefore a bit strange, because the pressure point is a bit harder. Once this moment has been overcome, the prototype drives almost like a normal Golf. On our test lap, the brakes always decelerate reliably and without any distortion in the steering. The drums even mastered ABS braking from over 100 km / h without noticeable problems. However, on our short test lap we could not find out whether this is still the case after the third emergency stop in a row. Why a GTI and not an electric car? The compact sports car is intended to illustrate that even vehicles with more power can be braked by drum brakes. A series development for such models is of course not planned.

But the bottom line is: It is exciting to see how little new drum brakes can differ from current disc brake systems. In small to medium-sized electric vehicles that take their main braking power from recuperation and thus from the drive, the technology can experience a renaissance.

Duo servo brake as the means of choice

In the case of electric cars, the Continental engineers also see the brake application area. In principle, drum brakes can be divided into different subtypes. the the simplest variant is the simplex brake. It has two brake pads, which are operated by a wheel cylinder. The duo-servo brake is significantly more complexthat the test car works with. Here the two brake shoes are also pressed against the drum wall by just one wheel cylinder, but the other end of the shoe is floating. This increases the braking effect.

E-cars could benefit in the future

The use of drum brakes on the front axle is still not an issue in the automotive industry. The engineers from Frankfurt firmly believe that this type of brake can do more than just support the rear axle. The prototype shows that it can work, but larger electric vehicles will probably continue to work with disc brakes.

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