Inflating ST trailer tires properly
Here is a quick and dirty way to inflate your ST trailer tires to the proper pressure. This is a modified version of the truck tire formula.
For the example I'll use my RV. My RV scales out at 8,020 pounds roughly and has a GVWR of 8,500 pounds. I'm running Transporter ST tires which are a Load Range E's stated for 2,980 pounds at 80 PSI. The Rv has 2 axles with 4 tires.All this information should be available on the trailer and on the tires. Tire capacity and pressure will be on the tires. Then GVWR should be on the trailer.
(GVWR / Number Tires) / Tire Weight Capacity x Max Inflation Pressure = Inflation pressure
8,500 / 4 = 2,125 / 2,980 = 0.71 x 80 = 57.04 PSI
I would most likely just round up to 60 PSI in my case and make note of the pressure requirement for the RV. Also remember to check the calculations with every new set of tires because rating do change from tire to tire.
So just for fun if I was to inflate the tire to 80 PSI max pressure those tires could carry 11,920 pounds or 3,420 pounds over GVWR. Just doesn't make sense in over-inflating a ST tire.
The modification to the formula was to use the trailers GVWR instead of axle weights for a few different reasons. First and foremost is most RV trailers or utility trailers can change weight rather rapidly for example running empty to get cargo, then loading up to near GVWR and heading home. So using the GVWR is the safest number. Then finding out some RV's like my own have a slide or two which might one side of the trailer a bit heavier. So going to GVWR again should cover for this. It's still up you to make sound judgements on what your inflating your tires too. This formula is to hopefully reduce the amount of explosive tire failures. What I found is most tire failures are cause because the tire are inflated to much and the tire can't conform to road debris or potholes so the tire either takes damage to the steel belts and/or violently explode because they can'r deflect the to the object.
I've been driving vehicles for 29 years now. Like my current truck it's got 251k mles as of right now. I've never experienced a explosive tire failure yet. Either on the tow vehicle or the trailers. I very rarely even have flat tires but when I have its usual the standard object in the tire like a nail or similar.
But I will throw a disclaimer... It is up to you to make sure you not over weight for the trailer in other words scale your loads, not travelling faster than the design speed rating of the tires, etc.