I would go up to the E range Maxxis even if your wheels are not rated for it if they are steel wheels. The likelihood of a steel wheel failing versus a tire failing are very good odds. I went to Maxxis E tires and run psi to match my steel wheel load rating (no psi rating stamped on it) which is less than the max psi the tire can be inflated to but better than the OEM tire rating at max pressure by about 400 lbs. In my case, unlike many, the rated wheel and tire capacity of the OEM exceeded the GVWR of my trailer but I like the reserve capacity nonetheless. BTW, I too have had excellent service from Maxxis ST tires. The last set of D rated tires lasted 6+ years