Originally Posted by TheSasks
I carry a 20 ton bottle jack (yes it is overkill but they have other uses when you live on an acerage) and put a piece of 2x2 on the frame rail between the tires then put the jack up against that.
That is what we do as well, although I use a 2x2 inch steel tube to distribute the weight along the frame.
Our fifth has a subframe that the axles are mounted to, then that assembly is welded under the camper frame. I am not sure if all campers with torsion axles have a subframe, but jacking on that subframe distributes the jacking force nicely along the main frame.
As our camper has a very light main frame, I would never jack directly on that, especially not without some kind of heavy bar to distribute the force. It would be very easy to bend the frame trying to lift the whole side of the camper on the head of a hydraulic jack. That would be a very undesirable result.