Dancing truck while towing

[Donna D.]

Originally Posted by ShelbyM

He's been coy but at 5000 lbs seems it has to be a Bigfoot.

Could be, or could be a slab-sided, boxy stick built. At one time he was thinking about putting a Scamp 5th wheel on a flat bed trailer.... hummmm.

[Steve Carlson]

What is the tongue weight?

[Silverback]

The height of the hitch may be an issue I tow a Bigfoot 21 rear bed with a Ram 1500 with air suspension. I initially set things up so that with the WDH installed the trailer was almost dead level, as was the truck. The BF21 is surprising light on tongue weight and I was getting a lot of bouncing and sway from the trailer, I think because my tongue weight was too light. Lowering the ball about 1-1/2 inches shifted the center of gravity of the trailer and put more weight forward. This made a huge difference in how this combo performed. And, truck and trailer are still pretty level

[redbarron55]

If it hits a dip and the rig dances then check the truck for a bad shock or shocks since it one is bad then that wheel will act faster and be undamped on rebound.
If shocks are bad then the truck might bounce more.
It is also possible that the truck is overloaded as well, but I assume that it is rated for the load.

[tmaken2157]

I have a 2012 Tundra with a 4.6L engine and I had the same thing happen over every bump found at bridges and overpasses, the truck would porpoise and that got old pretty fast, it only has 50K miles on it and my 2017 Chevy Silverado does the same thing.

I installed Timbrens from e trailer and its a job any back yard mechanic can do. They are basically bumpstops on steroids and cost 200 per set of two. Now with a bump the truck responds once and that's it. I use to have a Casita LD and now I have a 4500 pound camper.

[CarefreeLad]

Originally Posted by Raspy

Kevin,

Porpoising is a specific problem related to under-damped, low velocity compression and extension of the shocks. It is worsened by worn out shocks and/or velocity sensitive shocks.

The first thing to do is replace the shocks. Worn out or velocity sensitive shocks allow porpoising. So don't get just any kind as replacements. For instance, Bilsteins, which are very good shocks, work poorly for towing because they are velocity sensitive. Porpoising is very low velocity movement and can be outside the speed range of effective damping.

In my experience the best shocks for towing, or variable loads, are Rancho 9000 series adjustable shocks. You can tune them with the twist of a knob to be either soft for non towing or very stiff to prevent the problem you describe.

Do not just go to a cheap replacement, or to stock shocks that are designed to make the truck ride smooth when unladen. You need adjustable towing shocks.

full sarcasm mode - Awesome...just got a new set of Bilsteins!