CDL General Knowledge TestCombination Vehicles (if applicable)Hard
When inspecting the fifth wheel assembly of a combination vehicle, what is the significance of worn or missing kingpin locking jaws?
- AReduced steering response of the tractor.
- BPotential for trailer separation from the tractor.
- CIncreased air pressure to the trailer brakes.
- DDecreased fuel efficiency due to increased drag.
Show answer & explanationAnswer & explanation
Correct answer: B. Potential for trailer separation from the tractor.
The kingpin locking jaws secure the trailer's kingpin to the fifth wheel. Worn or missing jaws mean the kingpin is not properly secured, creating a severe safety hazard with a high risk of trailer separation.
Why the other options are wrong
- A. Locking jaws primarily affect the coupling, not directly the steering response.
- C. This is unrelated to the mechanical connection of the fifth wheel and kingpin.
- D. While trailer separation could cause drag, the immediate and most significant consequence is the separation itself, not just fuel efficiency.
Kingpin Locking Jaws
Components within the fifth wheel that secure the trailer's kingpin, preventing separation.
- Critical for safe coupling.
- Must be fully closed around the kingpin.
- Wear indicates a severe safety hazard.
Memory trick: Jaws that are weak, a trailer might leak (away).