There are several critical safety aspects to heavy vehicle combinations, one of which is couplings. Understanding fifth wheel couplings is vital to the safety and efficiency of any trucking fleet. We’ll dive into the world of fifth wheel coupling and what some of the best products on the market currently offer. 

What Is Fifth Wheel Coupling?

The technology of fifth-wheel coupling provides the connection between a semi-trailer and the towing truck, tractor unit, leading trailer, or dolly. A fifth wheel connects the two components, allowing them to articulate, move around, and steer comfortably.

Without a fifth wheel, it would be almost impossible for a semi-truck to make a turn. A fifth wheel evenly distributes weight between a semi-tractor and trailer so you can hit the road and navigate your equipment. 

What Does a Fifth Wheel Coupling System Consist Of?

As a whole, the fifth wheel coupling system consists of the fifth wheel and the kingpin.

  • Fifth wheel – This equipment is a flat, non-rotating horseshoe-shaped coupling device installed on the semi-truck tractor.
  • Kingpin – A metal component that protrudes from the trailer that’s frequently referred to as the “pivot point between the tractor and semi-trailer.” The kingpin on the trailer installs into the fifth wheel on the tractor. The semi-trailer’s surface, with the kingpin at the center, rotates against the upward-facing fifth wheel. 

Invest in High-Quality Coupling Systems With Advanced Technology

When you need to invest in high-quality coupling systems with top-of-the-line technology, look no further than JOST International. Our JSK37UBK Series wheel is revolutionary – it allows the driver to know when the fifth wheel is properly and safely coupled from inside the cab. The sensor technology in the wheel sends a signal to a display in the cab that lets the driver know when the wheel is properly coupled.


  • Throat Illumination (sold separately) – An LED Light shines into the throat to allow clear inspection of the coupled fifth wheel. 
  • Go Light – A green light indicates the fifth wheel is properly coupled, with both kingpin and handle in the locked position.
  • No-Go Light – A flashing red light with an audible alert indicates that the kingpin and/or handle are not properly coupled. 

Capacities & Ratings:

  • Maximum Vertical Rating: 55,000 lbs
  • Maximum Horizontal Rating: 150,000 lbs

How It Works:

  • The Loc-Light system enhances your JOST fifth wheel with the addition of our two-sensor monitoring system as well as a LED throat illumination. 
  • The dual-sensor system is connected to the Go/No-Go indicator light located next to the handle. A proper coupling with the handle and kingpin in the locked position will be lit up as green or “Go light”. If the system does not detect the handle and/or kingpin in the proper locked position, the light will flash red or “No-Go light” 
  • The throat illumination light option (sold separately) automatically turns on when the system is engaged. The light shines directly into the throat of the wheel to provide a better view of the lockbar for pre-trip inspections.

If you need to know how to couple and uncouple JOST fifth wheels, take a look at our instructional video.

Looking For More Coupling System Information?

If you’re looking for more information about JOST International’s coupling systems and top-notch technologies, contact us today. Our experienced team members would happily listen to your needs and share how we can help. We offer an expansive range of fifth wheels, kingpins, turntables, landing gear, coupling systems, and more.