It has been 2 years since I replaced my 16" GY tires/rims with 17.5" Michelins/rims from
www.trailertireandwheels.com and have yet to regret the expense for a moment. The one downside to the theory is the 62 mph rating on the tires--I cannot figure that out, but I can tell you that I don't stay below that speed (somehow, the new 450 setup lends itself to higher speeds until the wife alarm goes off). There is no evident wear on the tires, and no real loss of air pressure when stored, and I have over 12000 miles on the new tires/wheels.
There have to be other options on the market, but 4805lbs/tire has to contribute to long life and heat resistance.
Your results may vary...............
Joe