What Is the 5th Wheel on a Semi Truck?

The 5th wheel on a semi truck is an important component of the towing system. It is a large metal plate that sits on top of the truck bed and holds the trailer in place when it is connected and being towed. The 5th wheel mechanism consists of two parts: the kingpin and the jaws. The kingpin, which is permanently attached to the trailer, slides into a pocket in the 5th wheel plate, while the jaws firmly attach around it to secure it in place.

The 5th wheel was invented in 1933 by Charles Baskerville and has become one of the most widely used systems for trailer towing. This system has become increasingly popular due to its simplicity and efficiency, as well as its ability to safely tow heavier loads than other systems can handle. It also allows for more stability during turns and when negotiating hills or uneven terrain.

In order to ensure that your semi truck has a safe and secure 5th wheel connection, there are several steps you should take before hitting the road. Make sure that all nuts, bolts, pins, etc., are tightened properly before you begin your journey.

Additionally, inspect both the kingpin and jaws of your 5th wheel for any signs of damage or wear that might make them unfit for use. If you find any issues with either part, replace them immediately.


The 5th wheel on a semi truck is an important component of its towing system that helps provide stability when transporting heavy loads over long distances. To ensure your safety while out on the road, make sure all components are properly secured before beginning your journey. With proper maintenance and care, your 5th wheel should serve you faithfully for many years to come!

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Karen Watkins