Thor Forums

[Chance]

Originally Posted by Mustang46555

OK, here a twist. I just double checked the 8000 lb hitch on our Quantum class C.
To get the Road Master towbar level when hooked to an '05 Liberty I have a 2 1/2" RISER. So my added force is two and a half inches above the receiver center line. How does that effect the failure potential? Looking at the side plates on my hitch they appear almost double the thickness of those in the pictures and the bends have a large very noticeable radius to them. I wish there was a formula to multiply drop or rise by and subtract from the rated weight to get an idea where the safe range is. But I'm not smart enough to create it, any mechanical engineers in the crowd?

What you have sounds a lot better to me, but I’d have to see pictures to confirm it’s significantly better. The Devil is in the details as they say.

Keep in mind that these failures have occurred at receiver-to-chassis connection elevation, which is significantly higher than where the receiver centerline is on the receivers in question (not all receivers are built the same).

A 6” drop may extend total moment arm to close to 12” (more or less — would have to be measured), whereas your 2-1/2 riser would result in a moment arm of around 4” (again, would need to be measured). So yeah, I can see how it would be a lot better if your information is accurate and everything else is equal.

Just my 2 cents ....


P.S. — A simple formula as you mention is a bad idea in my opinion. There are too many variables to consider, which would lead to misuse. Perhaps the motorhome’s manufacturer could publish a maximum toad weight as a function of hitch drop (assuming level tow bar). That would shift responsibility to engineers at Thor and away from consumers who may not understand the physics involved. And in fairness, it’s not a simple problem to analyze.