“TANDEM” - For all of the reasons stated above. PLUS, I’ll add another and quite different reason. I often tow in fairly remote places, and I don’t like to be at the mercy of Murphy! I try to maintain my equipment, go to the excess on tires, bring lots of tools, and can do many roadside repairs, except.... a “burned” wheel bearing (unlikely, but it can happen). It happened to us 5 years ago, a few days before Christmas. Thirty-five miles from the nearest town, 140 miles to the nearest large city with parts, getting dark, temps in single digits and falling. Jacked-up the axle, removed tire/wheel, secured axle up to frame (you can use a short section of chain, ratchet strap, etc.), traveled another 65 miles to our campground near our son’s home on a single tire on the one side ( a strong case for “overkill” on tires). Enjoyed Christmas with family, drove to the big city (had a Dexter Axle supplier) after Christmas, bought parts needed (hub, bearings,grease). Right there in the campground with daytime highs in single digits to low teens, “dressed” the slightly damaged axle with a file, replaced all parts, and completed another chapter in our rv’ing experience!