[JRTJH]

If the specifications I found are correct (they aren't from the Keystone website, so they may not be accurate) the tires on that trailer were ST225 75R15 LRD (8 ply).

At the time of manufacture, most trailer manufacturers were not installing tires with any "excess capacity". It's only been within the last year that RVIA rules changed to require a 10% tire capacity above the anticipated tire load...

So, if I were to change out tires on that trailer, given it has 15" wheels, I'd install ST225 75R15 LRE tires and air them to 80PSI to achieve the maximum tire capacity. I would first inspect the wheels to be sure they are rated for that load (2830) and that pressure (80PSI)...

Given that we don't have the type of wheel (steel or aluminum) nor the age (possibly 17+ years old) or even the condition of the wheels (bent, rusted, corroded or in new condition) there's a lot more than just tire size/load rating to consider.....