Welcome!
With your coach loaded (people, supplies, stuff, as for a trip) go weigh it at a truck stop CAT scale. Then adjust tire pressure to what a load/inflation chart tells you to. If your tires are hot when you get to the scale, go 5 PSI higher than chart and set it accurately when cold the next day.
I can promise you it's way overinflated on the front, and that will make handling very squirrely. 55 may be enough for the rears. This is an E350 that made GVWR with "D" tires. You can use the "E" chart for "D" but not above 65 PSI and the respective weight.