Sailun tires versus Michelin

op wrote:
With the estimated actual tire carrying amount (weight versus tongue weight) should one have a tire that is rated to carry what might be on one side of the fifth wheel as in the case of a blowout of the other tire?

As was mentioned when one tire goes flat on a trailer with standard leaf spring suspension the tire behind or in front of the flat tire does not take all the weight. The flat tire is still carrying weight through the equalizer bar.

I am also assuming that tire inflation is based on carried weight, and that tires are quite happily run at under their full rated pressure.

Not for tires on a trailer. Nothing is gained by using 65 psi in a 80 psi tire other than a abused/hotter operating tire. Now 65 psi in a tire on the truck works fine.

Remember the tires on a truck are at the corners with the front set steering into the corner and the rears simply following. 65 psi in these tires won't hurt a thing. Little to non scrubbing issues.

Same tires on a trailer are close spaced in the center and actually slide sideways as the trailer goes around the corner. Using 65 psi doesn't hold the tires shape well and can lead to belt separation. Tire damage is cumulative so this practice may not show up right away.
Thats why industry experts tell us use a tire that can be operated at its max pressure when used in a trailer position.

I use the LT215/85-16 E at 2680 lbs on my 11200 lb trailer and keep 80 psi 24/7. I have around 47000 miles on them. Ran the first set for 55000 miles and no issues.

Don't try and over think how to select a tire for a trailer.