Originally Posted by The_Breeze
When you start jumping into the 22" ranges you start approaching tractor trailer tire sizes capable of more weight because they have more plies and the result is more psi to support that. Not that they can't build that into smaller diameters. They choose not to.
If the rim size is the same, then the aspect ratio conviction can be true and the sidewall flexes more. If you're comparing width, I don't think that necessarily affects load capacity without taking other factors into count such as air pressure and number of plies. A smaller width could introduce more sidewall flex because it bears more force on a smaller tread width. We can go into laboring detail on those physics for an eon and it's just not in me to do that anymore.
I think moving to 22 is a good, given the number of plies and their make up supports more load capacity (e.g. steel v. polyester v. fiberglass, etc)
Here's a lot on minutia on it for your entertainment
What I noticed on digging around and it was kinda buried in all of the info is the 19.5 inch tires only had a 6.75 inch rim which greatly restricts any larger tire. The 22.5 inch tires with 7.5 inch rims allow you to go up to f and j load range wider and tires if you wanted to. The 242" and 252" chassis with the 24,000# and 26,000# rating only come with the 22.5" tires.
I also found out I missed a chassis in there . The Miramar and the Challenger models each have 2 models that use a 262" chassis on the F53 frame with a 30,000# GCWR. Those appear to be the largest motorhomes Thor makes that still use the Ford chassis and engine.
No wonder my Vegas 24.1 has so much pickup. My little rig has the same engine and is 15 feet shorter than those big rigs! I have to feather the gas peddle at every stoplight to keep it from leaping off the line!