From the bloggers at Love Your RV.
A “pin box” is the part that connects your fifth wheel trailer to the hitch located in the trucks bed. The standard pin box you see on the majority of fifth wheels is solid steel with mounting holes on one end and the connecting kingpin on the other.
This does the job but since it’s a solid piece of steel it directly transfers forces between the truck, road, and trailer. On many road surfaces, this can lead to an uncomfortable ride and stress on the trailer frame and truck. It only makes sense to have some sort of cushioning and suspension system at this connection point. Most commercial tractor trailers utilize air suspension. Why not us fifth wheel RVers?
To read the full story by Love Your RV, click here.