There's a formula on Goodyear's website and a couple of other trailer tire manufacturers to set the inflation based on the trailer load rating, not the load rating of the tire.

The Endurance that I put on my camper had a max of 80psi and that's where Discount Tire inflated them. The trailer bounced around all the way home and cabinet door were open and drawers messed up. Ran it at the 65psi that the trailer manufacturer called out and they have been fine for the past 3 or 4 years.