CDL Combination Vehicles TestCoupling and UncouplingHard
A driver is inspecting the kingpin during a pre-trip. What specific wear or damage should be a primary concern?
- ALight discoloration or paint chips on the kingpin.
- BMinor surface rust on the kingpin.
- CGrease accumulation on the kingpin's shaft.
- DScratches or gouges deeper than 1/8 inch on the kingpin.
Show answer & explanationAnswer & explanation
Correct answer: D. Scratches or gouges deeper than 1/8 inch on the kingpin.
Deep scratches or gouges, especially those exceeding 1/8 inch, on the kingpin are a primary concern because they can compromise its structural integrity. Such damage can weaken the kingpin, potentially leading to failure and separation of the trailer from the tractor, which is extremely dangerous.
Why the other options are wrong
- A. Light discoloration or paint chips are superficial and do not affect the kingpin's performance.
- B. Minor surface rust is usually cosmetic and does not typically compromise structural integrity.
- C. Grease accumulation is normal and necessary for lubrication; excessive accumulation might indicate poor cleaning but not damage to the kingpin itself.
Kingpin Wear Limits
Specific criteria for inspecting the kingpin for signs of wear, damage, or deformation that could compromise its ability to securely couple with the fifth wheel.
- Critical for safe coupling.
- Deep gouges/cracks are dangerous.
- Must meet industry standards for integrity.
Memory trick: A deep gouge on the kingpin is a dangerous sign.