Tire inflation

[billd]

Let me try again I have a 2007 XL2 I have on the front. Michlin 365/70/22.5 on the duals I have 315/80/22.5 on the tag axle I have 365/70/22.5 what is the proper air inflation for each tire

[dale farley]

Bill,

The most accurate way to determine your proper air pressure is to weigh each axle then use the Michelin chart to determine the proper pressure. Even if you don't know the weight, you should be able to get a good estimate from the chart, but there is a broad range of pressures based on the weight. Here is a link to the Michelin chart. http://www.michelintruck.com/michelintruck/tires-retreads/load-inflation-tables.jsp

If I didn't know the weight of each axle, I would tend to go with a little too much instead of too little. If you have slides, I would definitely lean toward the higher side. I would think a good average would be a minimum of 120 in the front and 110 in all the rears based on the chart and not knowing the weight. As a general rule, if you add more presssure (within chart guidelines) than what you actually need, you are just making the bus ride a little more stiff. If you have too little pressure, you will start building heat and stressing the sidewalls. Tell us which conversion you have and if you have slides, and there may be someone else with a similar scenario.

[Joe Camper]

I think you typod the 318 80s are on the drives Right? and the 365s are on the tag right?


And the Steer those are also 365s right? I think that right. No slides you are about 22000 on the drive axle( GUESSING) so Id be asking the tire guy how much air in a 315 80 to carry 5500lb I guess 105psi PURLY A GUESS


Front axle not 20000 but probably north of 15000 but they went to the 365 so they had a tire that can carry a load wthout having to inflate it till it is a brick. The tag is going to be closer to 12000. The 365s on the front are a nessessity IMO and they are on the tag for decoration IMO

[Joe Camper]

OK typo corrected

A tire is normally rated for MAX load and that is whats stamped on the tire with the 31580 it is almost if not 10,000 at 125. psi (aprox a guess) I was a trucker not a tire guy so thats a guess but a close one. The ones on the drives on these campers are only carring aprox 5500 lbs each a small fraction of there max load.

You need a good tire guy or prevo or a michilan rep to find what you could drop those pressures to safley because your bus will probably ride smoother if you run less than max pressure.

Hope that helped

[jack14r]

Just weigh each axle and then use the Michelin chart,I would guess 115 on steer 100 on drive and I like the same in the tag.

[Joe Camper]

Jack cup just had the best race since Earnhart died. See it??

[Gil_J]

Bill,

First, I would recommend you review the Michelin RV Tire Guide available at this link: http://www.michelinrvtires.com/michelinrv/toolbox/reference-material.jsp

The only accurate way to inflate your tires is to measure the weight at each wheel position, 6 total measurements, with your coach fully loaded to include fluids, passengers, and all of your stuff. Use the weight of the heaviest wheel position per axle to determine the inflation for all tires on that axle. All state troopers responsible for motor carrier law enforcement carry enough scales to do this. You may not want to ask them given your weights will shock the troopers if they aren’t familiar with bus conversions.

The next best method is measure the weight per axle. Again, fully loaded find your nearest truck stop with CAT scales. Given the weight can be different from one side to the other add a safety factor. I’d compensate for a 500 pound difference, at minimum. So, axle weight plus 500 pounds.

The third best method is to use the ID plate near the driver’s seat installed by the converter.

The last method, and not recommended unless none of the above are available, is to use the maximum pressure ratings for the tire or wheel (whichever is less).

Except for the last method, I suggest adding 5 psi to the pressure calculated. This will make sure you are covered for some minor differences that may not have been planned for, errors in pressure gauge, and to add a small margin in safety. Always check and adjust tires when they are cold (the coach hasn’t moved and the tires have been exposed to direct sunlight for hours.

BTW, if you have 365s on the tag, I wonder why. I suppose it would be a great way of having a spare 365 for the front if needed. As you probably know, there aren’t too many vehicles equipped with 365s.