To further muddy the waters, use my funfinder tandem axle trailer as an example. I could in theory use a Kumho passenger tire, Solus KR21 215/70-14. Load cap 1554@44 psi. Minus 9% for fitting it to a trailer, equals 1414 pounds at 44 psi. This tire is allowed to fit to a 5.5 to 7 inch rim. My rims are 5.5".
Well look at that.... 1414 times two is 2828 pounds. The trailer has axles that are rated for 2800 pounds, so these lowly passenger car tires would exceed the load cap of the axles. :)
And, in my case, my trailer weighs 3974 pounds according to the local CAT scale, of which, about 3400 is on the axles. So I would have 5656 pounds of capacity carrying 3400 pounds, which is a 40% reserve.
Heh, heh..... I'd PERSONALLY run them before I'd run any ST tire ... :B