CDL · Combination vehicles
Before the tractor backs under a semitrailer during coupling, how high should the front of the trailer be?
Correct answer: Low enough that the tractor lifts it slightly when backing under.
Answer options
- ALow enough that the tractor lifts it slightly when backing under Correct
- BHigh enough that the kingpin sits about 2 inches above the fifth wheel
- CPositioned so the kingpin's tip is level with the fifth wheel's top surface
Why
At the correct height, the fifth wheel raises the trailer a little as the tractor slides beneath it. If the trailer sits too low, the tractor can strike and damage its front end; if it sits too high, it may not couple correctly.
About this question
Topic: Combination vehicles License: CDL
Part of these practice sets:
Where it applies: Asked in every state.
Practice the whole set
This question is part of Trailer Air Lines and Coupling (28 questions). Take the full set and check your score.
Practice Trailer Air Lines and CouplingMore questions from Trailer Air Lines and Coupling
- Before coupling, how high should the trailer sit compared with the converter dolly's fifth wheel?
- On a tractor-trailer, what are glad hands used for?
- When you drive a tractor with no trailer attached, why should its glad hands be locked together or onto dummy couplers?
- You are coupling to an older trailer and accidentally cross the air lines. What is the result?
- During coupling, your tractor is in front of the semitrailer but not yet under it. What do you connect before backing under?
- Which statement about air-braked semi-trailers built before 1975 is true?
- What must you confirm right before backing the tractor under a trailer?
- When the trailer air supply knob is pushed in, what does it do?
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