TOYO website should have the info to download after you weigh the rig to get the real weights. You'll also need the correct model and size of the tire.
I just weighed our front today, 18,030#'s and according to the Michelin chart that takes 105 psi.
That's what you need to do to get it correct but till then look at the side of the tire, it will have a minimum pressure to carry the maximum rating of the tire. It'll probably be too much but that's far better than too little pressure.
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft
Charter Good Sam Lifetime Member, FMCA, SKP
RV'ing since 1957, NRA Benefactor Life, towing '05 Odyssey