I just reviewed this page and found some great information but thought the chart to be a bit confusing. The biggest misconception is load rating multiplied by number of tires. 2 with a single axle and 4 for a tandem. Load rating D is critical for a singe axle in that 2200 lbs each tire time 2 equals 4400 lbs of load capacity. With the average rig pushing close to 4000 lbs loaded anything less than D would be hazardous. Tandem rigs are heavier but not that much. 4 1600 lb C rated st tires still carries 6400 lbs total which is typically enough. I still run Endurance D rated on my tandem for 8800 lbs of capacity which is serious over kill but worth the piece of mind.