I had a 2005 F350 SD CCSB Diesel 4 wheel with a 2011 855 Lance camper and when I weighed it with 2 people in the cab, full diesel tank, full fresh water tank and hot water heater, full propane tanks, a few tools, a 20 ton bottle jack, torklift superhitch and 32"extension but nothing else in the camper my weight was 11,920 lbs. My truck GVWR was 11,400 lbs. and my empty truck weight was 8,000 lbs. Once we loaded up the camper with food and supplies we were well over 12,500 lbs. I had upgraded my tires to 285/75r18 Toyo AT II Extreme which have a max load of 4,080 lbs at 80 psi. These were mounted on the factory Ford Aluminum rims. I also installled the Sumo Springs and the Tork Lift Stable Load. With these additions my truck handled the weight fine but I believe the 855S is a heavier unit than mine since it has a slide out.