Replacement Pin Box to Reduce Bouncing of 14K Big Horn 5th Wheel


I have a 14,000 GVW Big Horn 5th wheel. It has a standard Lippert kingpin box. It bounces quite a bit. I have quite a bit of flex in the box when I go over bumps on the freeway. Is there a standard for how much flex I should have? What would be a good upgraded king pin box for my application?


Expert Reply:

I am not aware of any industry specs on the maximum allowable flex. You might direct that question to the manufacturer of your fifth wheel.

The exact replacement pin box you need would depend on the model number of your Lippert pin box, as there are several different model numbers with # 1621 being the most common. There should be a sticker or plate somewhere on the pin box that will list the model number.

Since you are concerned about the bouncing, the Ultra-Fab TrailAir like part # UF35-946203 would be a good choice. The air bar provides cushioning, while the shock absorber ensures that the bag rebounds to ensure long life of the air bag.

If chucking (front to back movement) is also a problem, the TrailAir Tri-Glide like part # UF35-946229 uses steel rollers to allow some fore and aft movement to reduce chucking. Keep in mind, these will only replace a Lippert 1621.

If you would care to respond with the model number of your pin box, I would be happy to recommend some specific pin boxes for you.

expert reply by:
Mike L

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