Even since the Technology and Maintenance Council released its RP 750 report on the recommended practices for maintaining the “upper coupler structure of commercial van and flatbed trailers equipped with two-inch kingpins in a fixed-position coupler,” kingpin maintenance has not been given the importance it requires.


First released in August of 2008, RP 750 was an attempt to raise awareness of growing concerns. Though the task force’s co-chair, Bill Wahlin admitted that there was nothing of earth shattering importance in the report, but the VP of Engineering for Wisconsin-based Stoughton Trailers went on to state that a fleet’s technicians needed to be aware of possible problems. “Some fleets are going to use this as a tool to train their technicians and their drivers what to look for, and that goes a long ways.”

The task force’s other co-chair, Rob Nissen echoes this opinion. The manager of technical service/training pointed out that the upper coupler and fifth wheel have consistently been two of the least-maintained components on a truck. “The industry is in the frame of mind that it’s pretty much maintenance-free–it’s put together by the OEM, and once it’s put together it’s like there forever.”

This is, however, not the case. Sodium- and magnesium-chloride based agents have been used as de-icers over the past decade, and though not any more corrosive than previous mixtures, have proven to be more difficult to remove. These agents, road grit, and the grease on the fifth wheel assembly form into a rubbing compound that not only wears down the locks, but the kingpin itself.

This minor wear and tear may not be seen as much of a problem initially, but can prove to be catastrophic, claims Nissen. He should know. His Michigan-based company, SAF-HOLLAND, sees its share of winter wear and Nissen spends a large amount of his time traveling and speaking with fleet officials and dealers.

In an article on Goliath Business News, Nissen brought up this true story to accentuate the problem: “So this guy has a dry bulk tanker and he goes around the curve–his story is he was taking the curve at 10 miles an hour and looked in his mirror and saw the tanker going over. The fifth wheel stayed intact and locked and it severed the lower diameter (head) of that kingpin apart–it snapped it right in half, and the tanker went over. But when you looked at the condition of the kingpin after the accident, it probably should have been changed…”

As you can see, it is vital that a fleet inspect its kingpins at least annually. A kingpin repair service like this one can perform the inspection quickly preventing kingpin removal. Catching problems with the kingpin before they happen and refurbishing them, however, will save you time, money, and quite a large amount of worry.