Note that the side wall on the Michelin LTX (P) 235/75R15 XL tire says it is rated 2,183 pounds for car use, but it must be derated for truck/trailer use to 1,983 pounds per tire per federal regulation 49 CFR 571.110 section S220.127.116.11 to S18.104.22.168.
I use this tire on a 2013 25FB International with a GVW of 7,300 pounds and an actual tongue weight of 1,175 pounds camping ready. Thus the dual axles are supporting about 6,125 pounds or about a 1,531 pound load per tire which is a good load safety margin.
From reading this forum and learning of all the issues associated with the OEM GoodYear Marathon ST225/75R15D I switched to the Michelins as soon as I got the trailer home from the dealership.
We have a 2014 27FB Classic on order with a GVW of 9,000 pounds and a projected tongue weight of 1,100 pounds and net weight of 7,900 pounds on the axles. We are going to use the 16" Michelin LT 225/75R16E rated 2,680 pounds @ 80 psi.
If your 2008 30' Classic has a GVW of 10,000 pounds, then the net empty axle weight would probably be closer to 7,800 pounds or higher (exceeding the maximum capacity of the 15" Michelin per the regs) so the payload of a 16" tire would be required and give a larger safety margin.
WBCCI Life Member 5123, AIR 70341, 4CU, WD9EMC
TV - 2012 Dodge 2500 4x4 Cummins HO, automatic, Centramatics, Kelderman level ride airbag suspension, bed shell
2014 31' Classic model 30 twin beds, 50 amp service, 900 watt solar system, Centramatics, Dill TPMS, disc brakes, 16" tires & wheels