"off-roading" - frame twisting in a C

I don't like the idea of twisting the HOUSE part as much as a frame-twisting question implies. The very few rental contracts I've seen prohibit operation on other than surfaced roads. If the rental RV is returned without visible damage, it's all good. But most Class C's are going to be more leak-prone if they keep getting racked like that.

The frame is twisting all the time. It is a matter of degree. Just park on uneven ground and see how your house door behaves just a bit different. This translates into the house structure flexing on a conventional RV that is rigidly mounted to the frame. It's your call as to how much abuse you wish to subject it to. Phil's method of transiting rough ground is the sensible way.

The ones that 'barrel' are often using someone elses truck. I never, ever have felt the need to charge down any bit of nasty road surface. Washboard is THE worst because, as noted, it goes on forever. When I am in serious off road mode, it's slow and easy. I took a four wheel driving course, courtesy of the NPS in the Mojave and that is the most important thing that was taught. Slow and get out and l-o-o-k if you can't see what's next.


Gary Haupt

I'd say go even as slowly as 5 mph. I'm retired, have time, hate going that slowly, but do it anyway. My Tiger is on a Chevy 2500HD. Don't know what people might try with newer Tigers on 3500HD or the 3-point type on even heavier chassis.

Just as some FWIW comments:

Your Lazy Daze Class C is on an E450 chassis. One aspect of this chassis versus the E350 chassis is that the steel in E450 frames is thicker than that in the E350 frames (per Ford's specs). This will of course provide a more rigid platform for the box to sit on, thus not transferring as much torsion into the box structure as a lesser strength frame would. Supposedly this is one of the design differences that Ford built into the E450 over the E350 so as to handle the heavier loads. Of course for offroad travel - regardless of all other offroad design considerations - it's always best to use the heaviest duty frame possible under the lightest weight coach possible.

A couple of downsides to your setup in canted surface road situations is the sheer weight of your rig versus, say, a 23-24 foot Lazy Daze on the E450 frame ... plus your rig's internal wood framing within the walls.

A strength of your rig might be it's aluminum skin - if Lazy Daze does indeed use aircraft aluminum outer walls to go along with it's aluminum roof. Riveted aluminum outer walls would provide tremendous shear strength against twisting forces transmitted from the E450's frame due to canted road surfaces.

When we offroad in our 24 foot E450 Class C we go VERY SLOW (7-10 MPH) on washboard roads (we have aluminum framed walls) - so coach damage is a non-issue - we just need a lot of patience! We also travel on canted offroad surfaces VERY SLOW ... picking our track very carefully so as to absolutely minimize the front being twisted one direction (i.e. counter clockwise) simultaneous with the rear being twisted the other direction (i.e. clockwise). We absolutely CAN NOT "barrel along" offroads in our Class C like the bare/non-TC pickup trucks can do ... but we're retired so we have plenty of time.

However ... it sure is great to enjoy all the comforts of a small Class C out in the middle of nowhere where one would normally find only tent campers or truck campers!

I was up at monument vally with my PU and 10 ft slide in camper. Roads we like you describe, 1 way in/out. Anyhow thought I had broken a spring due to the twisiting, but there were lots of rental class c's going up down the trail. Not a good idea as you noted. The frames are not set up for that kind of twist action, neither are the bodies.

nomad 289 wrote:
What is the maximum diagonal height difference that the suspension will accommodate without twisting the frame?
...
What's a safe off-camber diagonal height for a normal C?

Spent most of my life in Africa and South America so I would not consider a half metre to be "seriously off camber" but rather a decent road.

That said:

-- The diagonal twist supported will depend on the vehicle in question. I tend to favor extended wheel travel.

-- Frame stiffness varies from vehicle to vehicle. Unimogs are notoriously flexible; Chevrolet pickups less so. Just depends.

-- Do pivot frames help? They can, if well done. But they are also tremendous stress raisers and can lead to a broken frame if poorly executed or overloaded. As a friend just found out, they can also fail, annoying when you are on the road in Siberia.

-- In my experience, vibration, as from washboard and pot holed asphalt, is a much greater danger than the odd twist, especially as the washboard goes on forever and you generally get over a bank a low speed.

-- Most Third World trucks tend to have fairly rigid body to frame mounts, intended to spread, rather than concentrate, the weight. The Australians, who have a lot of washboard, tend to favor conventional frame mounting with "pull apart" mounts that allow flex when required.

-- EVERY camper that has screw on doors (as opposed to bolt on) will see them fail with long dirt/bad road use. How much are you willing to spend?

So the bottom lines is, there is no fixed answer to your question. Unless you spend so much time in the dirt that you are literally pulling your camper apart, I wouldn't worry about it.

And, if you are, then you need to be looking at Tigers, Earthroamers, GVX, Unicat, et al. And you will be spending two to three times what you pay for a conventional Class "C" and you will still have things break. ;)

Safe travels!

I tend to balk at off-camber roads. I think my Tiger can probably take more of them than I can. I have not driven anything as much as 1.5 feet off-camber.

I've driven my Tiger about 55K miles, many of them on dirt roads or rough roads. Have gotten lots of "desert pinstripes" on the outside. No frame damage, no alignment problems. Had to retighten a few screws. I think that any RV owner should add a thorough screw check to the regular maintenance list.