Over on the commercial hauling side the Hercules H-901 in a LT235/85-16 G load/110 psi at 3750 lb capacity all steel tire is very popular on these type trailers with 7k axles. They should last for years on a RV trailer.
For 6k axles the Bridgestone R-250 and the Michelin XPS Ribs both a all steel carcass commercial grade tire in a LT235/85-16 E 3042 lbs capacity.
ST class tires the Provider ST235/80-16 or a ST235/85-16 both E load range/80 psi in the 3400-3600 lb range. This tire is OEM on some rv trailers.