Home › CDL Practice Tests › General Knowledge Questions › Question 370
When should the engine brake generally not be used?
- A.On slippery surfaces where its retarding force on the drive axles can start a skid, and where local rules prohibit its use
- B.On any downgrade
- C.Only at night
- D.Whenever the load is heavy
Correct answer
A. On slippery surfaces where its retarding force on the drive axles can start a skid, and where local rules prohibit its use
Why
An engine brake slows only through the drive tires, concentrating force where a slick surface offers the least grip. On wet, snowy, or icy roads that can break the drive axles loose, so service-brake technique and lower gears take over instead.
Manual topic: Engine Controls - Engine Brake Limits · From the General Knowledge practice bank (GK-370).