They don't call 'em "Marabombs" for nothing. Mine came off after about 4K and were replaced with Firestone Transforce HTs. Would have gone with BFG Commercial T/A, but the store was out of them. Some people go with the Michelin XPS RIBs, but that's the pricey option. Lots more rubber (like 30% more) and a higher speed rating on any of these tires compared to ST tires, even though I rarely go over 60 mph towing.
The weight rating is lower because the passenger car tire rating system is more stringent than the trailer tire rating system. So in the end given the factor of safety I decided they are much better than the ST-rated tires (and they really are). I will never run a "trailer" tire on any trailer ever again. -Greg