..What 'Executive' said. :)
I went through the same ordeal with our 36' Georgetown MH. Any time I get ANY service done on the MH, they insist on blowing up all the tires to their max. rated pressure. Even had one very argumentative tire tech. tell me that you should ALWAYS inflate the tires to the max. pressure shown on sidewall, regardless how much weight is on them. Like already said, guess they have to think that way, for liability reasons. Best way is to use the charts, though, based on actual weight numbers you get at a weigh station.
Forest River says 82 psi on the placard inside on mine. I weighed the rig fully loaded, using those numbers and Goodyear's charts, determined it should be around 84-85 psi. Added 5 pounds for safety, and set them all to 90 psi. Seems to ride great that way.