The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a device used to decelerate a motor vehicle, principally when the vehicle is traveling on long downgrades. Brake-retarders improve road safety and augment the functioning of wheel brakes.

Brake-retarders operate by switching the vehicle’s diesel engine to a compression mode, such that only air is supplied to the engine cylinders. A special gate is closed in the exhaust pipe, creating back pressure in the engine’s exhaust system and increasing resistance to the release of the air expelled from the cylinders. Operating in this mode, the engine does not develop power, but absorbs some of the kinetic energy of the automobile by using it to compress the air in the cylinders. Thus, the engine slows the rotation of the drive wheels, to which it is connected via the vehicle’s transmission.

Some vehicles with especially high load capacity and hydrodynamic transmissions use rotor-type brake-retarders, in which rotors with curved blades are installed on the drive shaft of the transmission. When the system is activated, oil is introduced into the housing, creating resistance to the rotation of the rotor and of the transmission’s drive shaft, which decelerates the vehicle.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.