As the private owner of a trailer, when you replace the tires with ones that have a higher load rating, the information on the tire placard related to the tires becomes meaningless. In fact, take a look at my fiver. The tire placard says to inflate the ST225/75R15 load range D tires to 65 PSI. Good luck mounting those tires on the 16" rims. Take a look at the tires, and you will see they are LT245/75R16 load range E. If you don't want to use the 80 PSI pressure listed on the sidewall for max load, then you can get an inflation chart for the tires and note the relevant information on the tire placard that says the GAWR is 5000 pounds to figure out what pressure to use. But lets face it, towing my trailer just a couple thousand miles a year, I can't wear out the tires having them inflated to 80 psi before the tires age out. So I run them at 80 psi. There are others out there in my situation as well. Some of the full timers may want to do something different, however, if they calculate a 15 to 25% margin, they may be close to max pressure on the replacements anyway.
