Weigh each end of the bus on a truck scale. Read the weight limit on the side
of the tire. Axle weight needs to be less than the tire limit x 2. My 40 foot Blue Bird
could theoretically be run on just two tires in the back without exceding the tire
limits. But why?
Take advantage of the "flat proofing" that the duals offer.
Check them every time you stop -- just give each rear tire a bump with your hand
or your foot or a hammer or other club. One day you may find a flat -- and you
have already made it to town and didn't even know you had a flat. Cheap insurance.