There are numerous posts on tire inflation in these threads.
Here is one such post
Many who are posting are providing answers based on their personal experience or what they have heard round the campfire.
As a Tire Engineer i would like to provide a slightly different perspective. One based on 40 years experience working for a major mfg. as many posts by non-engineers are not completely correct.
Your motorhome should have certification label (tire placard
) that the RV manufacturer applied to the vehicle. This
Here is a post on my blog on load & inflation
Also on gauge accuracy
The basic answer is that for motorhomes you need at least enough inflation pressure to carry the actual load on the tires.
Trailers should use the inflation on the tire because of unique side loading of tandem axles.
Until you get the real loading on each corner of your RV I strongly suggest you set your cold inflation to the inflation on the placard or 5 to 10 psi higher but not exceeding the inflation molded onto the tire.
Do you have any idea what your actual tire loading is? You provided the tire size but not the Load Range. Also what are the axle ratings on your placard. GAWR Front & GAWR Rear and what inflation F & R are shown on your placard? Having this information makes providing accurate answers easier.