Fifth Wheel
The coupling device on a tractor that connects to a trailer's kingpin.
Definition
The fifth wheel is a horseshoe-shaped coupling device mounted on the rear of a tractor's frame that connects to the trailer's kingpin. It allows the tractor and trailer to pivot during turns. Proper coupling and uncoupling procedures are critical safety skills tested during CDL skills exams. Drivers must perform a tug test after coupling and visually inspect the fifth wheel locking mechanism during every pre-trip inspection.
Why it matters to you
The fifth wheel is the connection you bet your load on. Coupling procedure is tested for a reason: an unlocked jaw or a high hitch leads to a trailer dropping in the yard or separating on the road. Do the tug test every time and look at the locking mechanism yourself. It takes seconds and it is the failure with the worst consequences.
FAQ
What does Fifth Wheel mean?
The coupling device on a tractor that connects to a trailer's kingpin.
Why does Fifth Wheel matter to a driver?
The fifth wheel is the connection you bet your load on. Coupling procedure is tested for a reason: an unlocked jaw or a high hitch leads to a trailer dropping in the yard or separating on the road. Do the tug test every time and look at the locking mechanism yourself. It takes seconds and it is the failure with the worst consequences.
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