Two years ago x-mas we purchased a R-pod-180.  I would be concerned with the stiffer axle items will shake and rattle more.  The cabinet underneath the fridge find it's way to the middle of the floor (all the screws shook loose) and all the items mostly dishes rattle and bounce in the cabinets.  Would highly recommend  balancing the tires, one was way out of balance.

Originally posted by Desert Wanderer Just bought a 2019 Rpod 180.. with a bent axle. Getting upgraded 5200lb axle installed as we speak, on leaf springs. Towing with an 08 VW Touareg. looking forward to fun times.

Congrats, and welcome!  How did the axle get bent?  What made you decide to convert to leaf springs? 

Thanks for the tire balancing recommendation, I'll get that done.

Ahh!  Bet it was overloaded both times.  Gotta weigh your rig.  I love my 180, and for what I do with it, it could hardly be better.  My Brittany and I work disasters from it.  But I don't see much heavy duty about it.  It feels like a Cessna, just enough, no more, flexes with a touch.  And, that's what I need, right now.  Gonna have to caution my GF about it.  She's a bit of a bull in a china shop.   

Be cautious.  Increasing the axle, and using it, could make the frame bend.

Agreed, not looking for more weight carrying capacity. Just looking for more margin when loaded.

If the heavier axle was another torsion axle it might be possible that that could increase stress on the frame rails, although unlikely. But a leaf spring axle will reduce frame bending stress. That is because the moment (torque) from the load on the torsion axle must be resisted by the frame. causing it to twist. And this twist is concentrated at a single point where the axle is attached to the frame rail. With a leaf spring axle there is no twist applied to the frame, the forces are vertical and spread out to two points (each end of the leaf spring). 

A good discussion of the mechanical engineering considerations is here:

https://mechanicalelements.com/trailer-axle-springs-torsion-axle/ - https://mechanicalelements.com/trailer-axle-springs-torsion-axle/

So changing to a leaf spring system could be a good move if the installation works out, looking forward to seeing the final results. 

BTW, the load on the spindle of the torsion axle is not increased by the inboard attachment points of the axle to the frame. What is increased is the load on the axle tube itself. So, if the spindle is what was originally bent that would still have occurred if the axle had been attached further outboard.

 Bottom line is that the 3500 lb axle is marginal for the application if the trailer is run near full load. You can get 2x or 3x bump loads from pot holes if you hit them wrong. That means you can get loads of up to around 3500/2*3= 5200 lbs on a wheel. 

The term "and using it" is ambiguous. If you meant that you should not use getting a higher rated axle to justify increasing the max gross trailer weight then I certainly agree, and I doubt anyone on this forum who has followed the rPod axle/spinde/frame/floor failure discussion over the past couple of years would disagree. That number is set by the trailer manufacturer based on DOT requirements. 

But no one, including Desert Wanderer, has suggested that. A more reasonable interpretation of "and using it" would be to use the higher rated axle to provide a better safety factor to reduce the risk of bending an axle on rough or potholed roads. In fact that kind of usage is what has been reported to have caused the original problem. Many folks have bent rPod axles that way, without having overloaded their trailers. I have run the axle tube calcs and the safety factor is under 2, while transport engineers generally recommend numbers more like 3 or higher. Several of us have now reinforced our axle tubes to mitigate this problem.

That was my interpretation of your statement.  I do agree that the trailer frame, although better able to handle positive g loads than the axle, is the next weakest link in the chain, There has been at least one bent frame reported on this forum, right where the FEA analysis shows the highest moments imposed by the torsion axle should occur. I simply pointed out that leaf spring axles have significant advantages over torsion axles in reducing bending moments on trailer frames, and provided a link to an engineering analysis demonstrating that.  

So perhaps I am not the one that has flown off the handle here. Choose your words more carefully next time.