Word forms: (regular plural) electric retarders
(Automotive engineering: Vehicle components, Brakes, steering, wheels, tires, and suspension) An electric retarder is an electromagnetic transmission brake that is only effective when a vehicle is moving.
⇒ There are conventional shoe brakes on all wheels of tractor and trailer, plus an electric retarder mounted on the drive shaft of the tractor and on a live axle of the trailer. ⇒ You will need to specify electric retarders to meet the regulations for use in such hilly terrain. ⇒ The coach driver said, "If I were to use the brakes on these mountain roads, they
would glow red hot and fade. That’s why I use the electric retarder".
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