So many variables in your question, Your coach should have a label/decal somewhere on a interior panel, closest, back of door or somewhere stating tire size and recommended pressure as built. You'd be best to use them. No matter what the coach really weighs, as long as you haven't exceeded the maximum weight rating, My advice is run them at that PSI. Invest in a good quality commercial tire gauge.
But no worries, there's a very large group about to descend on this thread with 500 opinions.....ha-ha.....(jokingly)
1999 American Eagle
ASE med/heavy certified technician
ASE advanced diesel certified