Originally Posted by TyCreek
Good article on tire pressures... one thing I note is his mention that the rig wouldn't be that heavy again but also says that extra 500lb was behind the rear axel ... if so, when that weight is removed it will ONLY lighten the load for the rear axel and in doing so it will actually ADD weight to the front tires.
That's an excellent point. Sometimes loading a vehicle may actually unload one of the axles -- typically the front axle. Therefore, if tire pressure is set based on maximum loaded weight, then occasionally running lighter overall may overload the front tires.
Most people can probably tell if that's ever going to be an issue for them, but if not, it may be worthwhile to weigh the motorhome both fully loaded and also as empty as you'd likely drive it; and then use highest load for each axle.
I fall in that exception. My van is an extended Ford E-Series with long rear overhang, and maximum load is when carrying a bunch of heavy stuff on a double-receiver hitch carrier that sits about 7-feet behind rear axle. For example, if I placed 400 pounds total on carrier, the front wheels will be unloaded by about 200 pounds. And the rear axle will get an extra 600 pounds instead of the 400 pounds.
In my case if I set front tire pressure based on maximum overall vehicle load, I could then overload the front tires when I drove without the heavy carrier hanging far off the back.
Looking at pictures of motorhomes with long rear overhangs that have a large rear cargo area, and/or carry extra weight on a rear cargo carrier, it's easy to see how this could happen. This picture is a good visual on how extra load could unload the front tires.