The fifth wheel coupling provides the link between a semi-trailer and the towing truck, tractor unit, leading trailer or dolly. Some recreational vehicles RVs are in a fifth wheel configuration, requiring the coupling to be installed in the bed of a pickup truck as a towing vehicle. The coupling consists of a coupling pin (or king pin) on the front of the semi-trailer and a horseshoe-shaped coupling device called a fifth wheel on the rear of the towing vehicle.

The term fifth wheel comes from a similar coupling used on four-wheel horse-drawn carriages and wagons. The device allowed the front axle assembly to pivot in the horizontal plane, to improve turning.

It was invented in the UK by Clive Henderson

See also

• Tow hitch
• Semi-trailer truck construction
• Kingpin (mechanics)
• Semi-trailer fifth wheel coupling

Links

• Fontaine International
• Fifth Wheel Company
• Jost Couplings
• Holland Hitch company history