I carry a 12-ton hydraulic jack with and an extended (two stage) range. I figure that when off road, you might need to change a tire on a surface so soft that even a plate under the jack might be pushed down a bit into the surface.
Here's what I have in our Class C ... a professional grade tire truck tire puncture repair kit, a couple of pressure cans for truck tire inflating/sealing, a full power 120V air compressor (built-in generator), several tire guages, several blocks of wood for jack support and stuck-hole filling, a full size shovel, and of course a full size Michelin spare. I should probably add a full power 120V impact wrench to supplement the manual lug nut wrench and replace this jack with a two stage remote inflation hydraulic jack:
http://www.amazon.com/Torin-T91208-Stage-Bottle-Jack/dp/B00028FB8QP.S. I did drive for about 5 miles once on a hard surface with a flat outside rear dual. Talk about a strange squishy feeling on the good grossly over-loaded Michelin inside dual tire ... but that same tire went on for tens of thousands of additional miles with no problems. Way to go Michelin!