How To: Figure out LT tire pressure

[Adondo]

Good info, and this comes up all the time on the RV.net forums.

Take my motorcoach for example. The rear axle weighs 17,800 lbs., the front 9,600 lbs. Just because the Toyo M120z tires which are mounted on 22.5'' wheels say 120 PSI max doesn't mean they need to be blown up to that amount. According to Toyo's charts for the tire's particular size, the rear tires (the PSI pressures per weight are different if they're dual) run 100 PSI. The front axle tires run 105 PSI. That's a helluva lot less than the 120 PSI max. If they were maxed, they would wear out in the tread center.

Commercial vehicles which can include heavy RV's, always need to be weighed and a tire manufacturer's chart consulted before just guessing as what to put in a tire. It shouldn't be any different for our Jeeps. Especially the Commander for that matter, as it's a heavy rig. My XK weighs a bit more then our Ford Expedition in fact, despite being a smaller vehicle. An XK is a stiff as a Tonka Toy for a reason. (Very little body twist)

[fosh69]

So question: has anyone weighed the front and rear to see what the weight over the axle actually is? I have a 5.7 over the front, and other than a few pounds here and there for add-on's, I would think it's going to be close to the same all the time, right? The load in the cargo area may affect front weight over the axle, but probably not by much. As a rule, being a truck guy, I have always run more pressure in the front tires (usually about 2psi) unless I'm loaded. Any input on this? Thanks.

[Matt]

I used to run 3-5 PSI less in the rear tires of my pickup truck as well.

For my Commander i run them all the same pressure. I'm not sure what the exact weight distribution is on these vehicles, but it looks to be pretty close to even.

My "standard" procedure is to run them all the same unless i see signs that pressure should be reduced, ie: the center tread of the rear tires wearing more, or non-uniform tread contact patch.