Home › CDL Practice Tests › General Knowledge Questions › Question 131
Before backing under a semitrailer, what should you check about the trailer height?
- A.Height does not matter if you back slowly
- B.The trailer should sit slightly lower than the center of the fifth wheel so the wheel lifts it gently as you back under
- C.The landing gear should be fully retracted first
- D.The trailer should be a foot higher than the fifth wheel
Correct answer
B. The trailer should sit slightly lower than the center of the fifth wheel so the wheel lifts it gently as you back under
Why
Set correctly, the fifth wheel slides under the apron and raises the trailer a little, which keeps the kingpin aligned with the jaws. A trailer that is too high can let the kingpin pass over the jaws or damage the fifth wheel, and one that is too low can be rammed by the tractor frame.
Manual topic: Combination Vehicles - Coupling · From the General Knowledge practice bank (GK-131).