CDL Combination Vehicles TestInspecting Combination VehiclesMedium
During a pre-trip inspection, a driver notices that the trailer's fifth wheel skid plate has insufficient grease. What is the primary risk associated with this condition?
- AIncreased wear on the kingpin and fifth wheel jaws.
- BDifficulty in coupling/uncoupling the trailer.
- CReduced air pressure in the trailer's brake system.
- DOverheating of the trailer's wheel bearings.
Show answer & explanationAnswer & explanation
Correct answer: A. Increased wear on the kingpin and fifth wheel jaws.
Insufficient grease on the fifth wheel skid plate increases friction between the trailer and the fifth wheel. This excessive friction leads to accelerated wear on the kingpin, fifth wheel jaws, and the skid plate itself, potentially compromising the coupling's integrity.
Why the other options are wrong
- B. While it can make coupling/uncoupling more difficult, the primary safety risk is the accelerated wear and potential failure of critical components.
- C. Fifth wheel lubrication does not affect the air pressure in the trailer's brake system.
- D. Wheel bearing overheating is related to bearing lubrication and adjustment, not fifth wheel skid plate grease.
Fifth Wheel Lubrication
Proper lubrication of the fifth wheel skid plate with grease reduces friction between the tractor and trailer, preventing excessive wear on coupling components.
- Reduces friction during turns and vehicle movement.
- Prevents premature wear of the kingpin and fifth wheel jaws.
- Ensures smooth and safe operation of the combination vehicle.
Memory trick: Grease is the word for wear, not despair!