What Is a Kingpin on a Semi Truck?

A kingpin, also known as a fifth wheel, is an important part of a semi-truck that connects the tractor to the trailer. It is the pivotal point between the two vehicles and is essential for ensuring a safe and secure connection.

The kingpin is typically built from high-strength steel and is designed to last for many years with proper maintenance.

The kingpin consists of two parts: the pin and the socket. The pin attaches to the tractor, while the socket attaches to the trailer.

The pins are secured to the tractor with large bolts that require regular maintenance and lubrication in order to ensure a safe connection between vehicle components.

When properly installed, a kingpin should have no play or movement whatsoever between its two components. If a kingpin has any play or movement, it can cause excessive wear on both vehicles and can lead to an accident if not addressed quickly.

In addition to connecting the tractor and trailer together, the kingpin also provides stability while in motion. Without it, semi-trucks would be unable to safely turn corners or make tight maneuvers at highway speeds.

Maintenance of Kingpins

Kingpins must be routinely inspected for signs of wear such as cracks or corrosion. If any problems are found with your kingpin, it should be replaced immediately by a qualified mechanic in order to ensure your safety on the road.


What Is a Kingpin on a Semi Truck? A kingpin is an essential component that connects a tractor and trailer together securely and safely.

It also provides stability for turns and tight maneuvers at highway speeds. Regular maintenance of this part is essential for keeping drivers safe on the roadways.

Photo of author

Susan Delgado