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Why can using an engine retarder on a slippery road cause a jackknife?
- A.The retarder adds air pressure to the trailer brakes until they lock
- B.Retarders reverse the rotation of the drive tires on wet roads
- C.A retarder shuts off the trailer service brakes completely
- D.On low-traction pavement the retarder can slow the drive wheels enough to make them skid while the trailer keeps pushing forward
Correct answer
D. On low-traction pavement the retarder can slow the drive wheels enough to make them skid while the trailer keeps pushing forward
Why
An engine retarder brakes only through the drive axles, and on ice or wet pavement that force alone can break the drive tires loose. When the drives skid and the trailer keeps rolling, the tractor can be pushed around into a jackknife, so many manuals advise turning the retarder off on slick surfaces.
Manual topic: Combination Vehicles - Skids and Jackknifing · From the Combination Vehicles practice bank (CV-133).