Originally Posted by Mr Sunshine
If your tires are Michelin, they have a section on their website that will give you suggested PSI for your rig.
I found that their recommendation is the same as the chart that Thor puts inside the coach. Sometimes it is on the wall near the driver, sometimes in a closet. The suggested PSI will be for fronts and rears, usually different.
That michelin chart, as I learned form an engineer at Yokohama, is numbers that are put out by some wheel and tire professional association.... I've forgotten the name now... Anyway those are standard numbers based on tire size, and will work for any brand...it's just that some companies publish the numbers and some don't...Michelin chose to publish them....
when in doubt, fill it to the max suggested in the door post. Ride and handling will suffer at lighter weights...but that's the safe move.
Get weights...each axle or better each corner... then by that chart you can reduce the pressure with lighter loads for better ride and handling.