My coach is a 2005 Newmar Mountain Aire 4304. It's a 43 foot RV Class A diesel with tag axle. According to the sticker inside the RV, it has a Max GVWR of 44,200. The front GAWR is 14,200 lb and the rear GAWR is 30,000 lb.
The tires are 2 year old Toyo M144A in size 295/80R 22.5 They're marked as Load Range H. They're all in excellent shape.
I've located the Toyo Tire Commercial Load and Inflation Tables. I believe it's the correct one. I'll try to attach a link to the online tables that I'm using. I'm hoping that will work.
Anyway, the table gives various pressures and associated loads the tire will carry at that pressure, I presume. Assuming that's correct, based upon differing pressures, the tire will support between 4920 lb and 7830 lb each in a single configuration. If I understand this correctly, I would double that figure for an axle with two tires on it. That makes the front easy - my axle can't have any more than between 9840 lb and the max gross GAWR of the actual axle which is 14200. At 14,200 lb, the tires would need a max pressure of between 105 - 100 PSI. Of course all this depends on having the coach weighed fully loaded up as it would travel and seeing what the actual front axle weight is. Assuming for example the front axle actual weight came in at 13,900, I would inflate the front tires to 110 PSI, giving them a load capability of 7065 lb each, or 14,130 for the axle. Assuming I'm pretty close on my understanding of this (I hope) then the front end of things is fairly straightforward.
Now we get to the back, and the dual (tag) axle setup. Now, I'm clueless. Do I weigh each of the axles separately? How do I do that? The weights on the Toyo Tire tables are shown as both single and double. Do I count the tag as single and the drive axle as double? Do I use the single figure and multiply by 3 on each side? I'm just clueless here as to how to properly do this.
The GAWR of the rear is given as 30,000. I assume that's a total for both tag and drive axles combined? Do I just treat them as one with 6 total tires? Do I use the single or dual numbers? This is very confusing!
Also, why are the load bearing numbers at a given pressure lower for dual vs. single at the same pressure?
If I have to weigh the drive vs. tag axle separately, how do I do that?
Is it safe to say that for quality of ride you want to run the minimum pressure you can that will support the actual weighed load on that particular axle?
I'd appreciate any help you more experienced guys can give me on this. Thanks!