Originally Posted by RV_TireMan
In response to your question -- the 315 series tires should be mounted a 9" wide rim - 8.25" rim is too narrow for the 315/80R22.5.
Hope this answers your question and safe travels to you and your family
The puzzling thing is that some tire makers do not quite have that requirement, or are "walking back" what they might have said earlier.
Here's the Continental spec on their HR2SA which allows 315/80R22.5 tires on 9.25 rims but downrates their capacity to 7610#@120psi. Note that the 295/80R22.5 tire is listed at a capacity of 7830#@120psi.
I know many, like Michelin, used to derate their 315's when used on an 8.25 wheel but now no longer recommend that combination "for vehicles produced after Jan ]1, 2018". Sounds like lawyer language to me. Here's their page for the X-Line Energy Z.