The conventional wisdom is that dual rear wheels follow ruts in dirt roads more than singles do, and are more difficult to drive through snow and deep sand because the rear wheels don't ride in the track of the front wheel. However, trucks with dual rear wheels are driven just about anywhere there's a semblance of a road. Many fire department brush trucks are driven off-road with dual rear wheels. Having dual rear wheels doesn't keep beer delivery trucks from reaching some very out-of-the-way locations!
Dual rear wheels can pick up a stone between the tires. If the stone is not removed, it can rub through the sidewall of the tire, resulting in a blowout and a tire that shouldn't be patched.
Because single tires have a lower load rating than a pair of tires do, the single rear tires often have to be larger to give you enough carrying capacity for your camper and gear. Sometimes it's not possible to fit the larger size tire at the front wheel because of interference with the fender or suspension. So you might be tempted to use a different size tire front and rear. That means carrying two spare tires.
Switching from 16 or 17 inch rims to 19.5 inch rims is one way to get tires with greater carrying capacity. This works OK in North America, where 19.5 inch tires are not difficult to find. Outside North America, the common tire sizes are 16 and 22.5. You might not be able to find a 19.5 replacement without considerable delay and the expense of shipping the tire to your location.
Another issue with single rear tires is you may have to run a high tire pressure to gain the load capacity. If the tire is subjected to unusual loads, you don't have any excess capacity. For example, on a severe side slope, most of the weight of the truck transfers to the tire on the low side. Running duals usually gives you more excess capacity.
When looking for tires with greater carrying capacity, be careful that the diameter of the tire does not increase too much over the stock tires. If you want a taller tire, you may need to re-gear the differentials to maintain acceleration at an acceptable level.
Bottom line: Switch to single rear wheels if it's possible without major expense. Otherwise, run duals and don't worry about it.
Comparing the 2004 Cummins with the 2007 model, I think the 2007 requires ultra-low sulfur diesel fuel. Today, this fuel is not available outside western Europe, Canada, USA and a few Mexican stations close to the USA border. If you plan to drive south into Mexico and Central America any time soon, you should keep the 2004 model.
Chip Haven
