Yes, "S" means 112MPH. 110 means 2337# and 107 means 2149#. That means your Front Tires can carry up to 2337, and each rear dual tire can carry 2149. Tires are rated to carry a little less in the dual application than the single.
What Max Air Pressure does the Sidewall show? My guess would be 65PSI meaning Load Range "D" which is the old "8 Ply Rating". Most of the tires in your size sold now are at Load Range "E" or 10 Ply. You may hear them called E-Ten and that has nothing to do with Ethanol in your fuel tank. Go ahead and get E-Ten. You won't increase the capacity of your chassis but you'll have tougher tires. Weigh your coach and see what your axle weights are. I think you'll find you're in the D-Eight range and any quality Load Range E (E-Ten) tire will please you. I just this week installed new Bridgestone Duravis 250 tires which are a commercial duty tire. I did it because our axle loads are very close to max for this tire size even in E-Ten. The Michelin XPS Rib is another tire in that category. If I had a lighter coach, which yours should weigh out to be, I would look hard at Firestone TransForce. The Michelin LTX M/S2 would be a step up. Excellent comments on both of these. Michelin LTX used to crack but the impression is that it's been corrected on M/S2.
