If you give needed data , I will give a picture of my filled in spreadsheet in my answer with adviced pressure for your situation.
From Motorhome ( I asume its not a travel trailer or 5th wheeler)
Best would be seperate weighed Wheel( pair ) loads , second best axle loads weighed, but in lack of that we will have to do with the GAWR's and GVWR ( Gross Axle/Vehicle Weight Rating).
Maximum used speed , wich you wont go over for even a minute.
Configuration of Motorhome ( number of axles and total tires rear and front. GAWR's and GVWR mostly are on same plate as pressure advices in America, European cars must have a VIN-plate with it since about 1980.
From tires : Maximum load and AT-pressure ( wich is not the maximum pressure) but also speedcode of tire ( between J and Q )
Handy would be the sises of tire to check with Google if your 80 psi AT-pressure is realy the AT-pressure. Mostly this all can be found on sidewall of tire.