The whole mantra of ST tires, "must be inflated to maximum pressure" is a pain in the ass. I tried. Given the way psi fluctuates with temperature, I felt like I needed to adjust tire psi every morning. Add in the normal deviations of tire pressure guages, and it felt like a lot of work that still led to failure (blown tires). The concept that the tires must be at maximum pressure to carry any load seems to be a tire manfacture's way to dodge responsibility for making cheap tires. Small wonder that when I complained to the tire manafacture's rep, one of their responses was that your tires were under-inflated.
Since I switched to LT tires with a higher rating, and added a TPMS systems, my morinings before getting on the road are a lot less sweaty. Initially I inflated the tires to 100 pounds at 85°. In real life, I am comfortable starting on the road with a tire pressure range from 90 - 105 psi - the air compressor has not been out of the tool bin since the switch. Actual psi when running on the road is between 100 - 120 psi, depending on the actual outside temps. My alarms on my TPMS are set at 85psi low, 125 psi high.
I am using Hankook F19 7.50/r16, load range G. I picked these tires on recommendation of a friend who had 5 years experience running Hankooks. One big factor for me is that they fit the width of the rims that came with my trailer. Max inflation for these ties is 105psi.
My rims are rated at 110 psi. I did not change the valve stems when I changed tires. Turns out the valve stems the came with my wheels were only rated for 80 pounds. It was 14 months before one failed - on I-75 in Macon, GA - 95° and 90% humidity. The TPMS gave plenty of warning and we were off the road before the tire fully deflated.
I had a puncture flat in one tire 2 weeks ago. A small nail went in the tire and created a very small leak. It would not leak while under way, but would lose air over night. I tried to fix the tire while still on the trailer. I wanted to use a "gummy worm". The dam tire was so tough that I broke the gummy worm insertion tool when I was trying to put in the plug. I finally pulled the wheel off the trailer and took it to a local tire repair shop for an inside patch (better method of repair).
The change to LT tires and the use of a TPMS has made travel a lot less stressful.
The gross of my trailer is 13,800 pounds. My hitch weight is 2400 pounds. The 11,400 pounds carried on my axles amounts to 2,850 per tire. Even using the consertive "all uses" load rating of the Hankook LT tires (3330 pounds), I have a generous safety margin for load variances.
ST fail pics (my tires):
FWIW, I tried to get the tire manafacture to pay for damages to my trailer. It took a week to track down the responsible party, Dynamic Tire Corp (Power King Towmax). Initially, they claimed my tires were out of warranty (14 months). Then they said the blown tire was destroyed, and could not be analyzed for cause of failure. I was lucky to have one tire that showed damaged without being blown, so I had a lever to use in negociation lever. Next I had to work through the "under-iflated" line. After ~ 5 months, the distributor agreed to buy my ST tires back at $125.
Disclaimer: I am a retired telephone man, not a tire expert. My knowlege, if correct, was learned the hard way. My situation may not match yours.