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Brake-by-wire (literally: braking by wire ) describes a braking system in which the actuation and transmission devices are decoupled from each other. In the conventional hydraulic brake system, the actuating device is the brake pedal and the transmission device is the hydraulic system . A distinction is made between electro-hydraulic brakes , electro-pneumatic brakes (on trucks) and electromechanical brakes.

Only when hydraulics or pneumatics are dispensed with does the brake become a real, so-called “dry” brake-by-wire application, as no fluid-technical systems are used here. At the IAA 2005, Siemens VDO Automotive presented a car brake based on wedge technology , which should go into series production by 2010.

The future use of this technology was justified primarily with the inertia of the media currently used in the braking system. With the help of exclusively electromechanical solutions, shorter response times could be made possible, whereby this should also be reflected in the achievable braking distances. An important advantage is that brake-by-wire technology can be manufactured much more cheaply, since components used in hydraulic systems, such as master brake cylinders, brake boosters and ABS , have to be manufactured in a comparatively complex manner. In the future, all functions of the braking system can be implemented using software.

A visible disadvantage is the legal requirement for a fall-back level, so that the brakes can still be operated in the event of a fault in the electronics. In the case of the electrohydraulic brake, this means only one additional valve which is open when no current is applied and which restores the coupling between the brake pedal and a hydraulic circuit (preferably that of the front axle). With the electromechanical brake, a second battery would have to be made available and redundant signal lines laid. However, a second battery represents, among other things, a considerable difference in weight and is therefore not practical.

Brake-by-Wire has been used in the Formula 1 World Championship since 2014 , where the system electronically distributes the braking force between the recuperation brake and the mechanical braking system on the rear axle of the vehicle.


  • Karl-Heinz Dietsche, Thomas Jäger, Robert Bosch GmbH: Automotive pocket book. 25th edition. Friedr. Vieweg & Sohn Verlag, Wiesbaden 2003, ISBN 3-528-23876-3 .