I could use some verification of the tire pressures for my motorhome. I think I have this right, but I sure would like someone who knows more to confirm if I do.My coach is a 2002 Monaco Diplomat 40’ with three slides. As I cannot find a location to do corner weights yet, I have just used a Cat scale to measure the axle weights. The GVWR on the coach is 32,000 lbsActual WeightWeight with full fuel and water with two people onboard = 28,635 lbs.Front axle = 11,185 / 2 = 5,593 lbs per tireRear axle = 17,450 / 4 = 4,363 lbs per tireI pasted below what the Goodyear chart showed. The chart I found this info on can be found here http://www.goodyearrvtires.com/pdfs/tire-care-guide.pdfGoodyear 275/70R22.5 load range HPSI 85 90 95 100 105 110 115 Singe 5170 5400 5630 5850 6070 6290 6510 Dual 4770 4980 5180 5390 5590 5800 6000 Now, using the above chart, I have concluded that my front tires should have 95 psi, and my rear tires should have 85 psi.After reading in forums, these pressures seem low? Most seem to be running in the 100-110 psi range?Can someone advise me if I have interpreted the Goodyear chart correctly, and these seem to be the right pressures for my tires?(Sorry, I can't get the formatting right to display the chart info.)Thanks

Yes, you figured correctly at 95 and 85 pounds. Now if I were doing it, I would run 100 pounds in all the tires for the sake of simplicity. After all, the tires are going to age out before they wear out so even wear is not a concern. Also, with the little extra air pressure the front tires will run a little cooler and it should not effect the ride quality.

Filled the data in my calculator and made a special map for you on my one drive in the examples map of motorhome RV map.This uses the list from goodyear for your sise and H-load , but there are 2 , botom is for G159 wich gives 2 LI steps lower maximum load then the one above.In case of daubt always use the lowest maximum load or highest AT-pressure ( here 125 psi instead of the common 120).All this filled in gives next picture .Notice that this is for maximum speed of 75m/h, you can even use higher pressure with lesser deflection , the deflection that would be needed for 99m/h , and then still no bumping .This would need Front 132 psi and rear 108 psi, and would give maximum reserve for things like pressure loss in time and misreadings of pressure and weight and misyudging of weight, etc, and then still no bumping and still acceptable gripp.So dont be affraid to use these high pressures , tiremakers allow 20 psi above At-pressure of here 125psi , and you must be having metal valves wich can stand above 145psi cold pressure.Your map is placed in my examples map here at front with your name . If rightclicked you can download the complete map to your computer. Leftclicking opens it , and I will also put a picture of Goodyears list in it with your tires highlighted.The examples map with your map at front.

You're running the coach pretty light considering how much room you have between measured weight and GVWR. You read the chart correctly but if you had the coach weight checked with the rig more or less empty then you might run into under inflation problems later. What you could do is use the numbers, 95 and 85, as never go below pressures but inflate the tires up to the maximum front and rear axle load limits if you have a concern for the low numbers.

Your numbers are correct and most of us go 5 pounds over the base pressure. Over the years I've had to increase the pressure as we keep too much stuff.In Oregon I do corner weights because they leave the scales on even though the weigh station is closed and you can get off to the side.

Also seached the tire sises and loadkind from Michelin.Will give both pictures in this post and below that will give my idea what has been done here.First the goodyear data and now same sise from Michelin.What to my opinion has been done by goodyear is that the tire was originaly calculated in maximum load for 9 bar wich is conversed to 130 psi.this gives single 6940 lbs maxload = LI 148, wich is also given at Goodyear list list at top for 125 psi.Later they realised that for 125 or 120 psi the maximum load has to be recalculated to lower.The G159 list gives 6610 lbs maxload at 125 psi wich is Loadindex 146. If you look at Michelin list at 125 psi you see 13460 axle = 6730 a tire loadcapacity wich is yust below LI 147/6780 lbs so rounded down to LI 146. So this strongens my opinion to use the lower maxload tire in the goodyear list.

Yet another tire pressure question. | Good Sam Community

14 Replies

Ivylog
Explorer III
Apr 29, 2015
Your numbers are correct and most of us go 5 pounds over the base pressure. Over the years I've had to increase the pressure as we keep too much stuff.
In Oregon I do corner weights because they leave the scales on even though the weigh station is closed and you can get off to the side.
Dale_Traveling
Explorer II
Apr 29, 2015
You're running the coach pretty light considering how much room you have between measured weight and GVWR. You read the chart correctly but if you had the coach weight checked with the rig more or less empty then you might run into under inflation problems later. What you could do is use the numbers, 95 and 85, as never go below pressures but inflate the tires up to the maximum front and rear axle load limits if you have a concern for the low numbers.
jadatis
Explorer
Apr 29, 2015
Filled the data in my calculator and made a special map for you on my one drive in the examples map of motorhome RV map.
This uses the list from goodyear for your sise and H-load , but there are 2 , botom is for G159 wich gives 2 LI steps lower maximum load then the one above.
In case of daubt always use the lowest maximum load or highest AT-pressure ( here 125 psi instead of the common 120).
All this filled in gives next picture .

Notice that this is for maximum speed of 75m/h, you can even use higher pressure with lesser deflection , the deflection that would be needed for 99m/h , and then still no bumping .
This would need Front 132 psi and rear 108 psi, and would give maximum reserve for things like pressure loss in time and misreadings of pressure and weight and misyudging of weight, etc, and then still no bumping and still acceptable gripp.

So dont be affraid to use these high pressures , tiremakers allow 20 psi above At-pressure of here 125psi , and you must be having metal valves wich can stand above 145psi cold pressure.

Your map is placed in my examples map here at front with your name . If rightclicked you can download the complete map to your computer. Leftclicking opens it , and I will also put a picture of Goodyears list in it with your tires highlighted.
The examples map with your map at front.
Grandpere
Explorer
Apr 29, 2015
Yes, you figured correctly at 95 and 85 pounds. Now if I were doing it, I would run 100 pounds in all the tires for the sake of simplicity. After all, the tires are going to age out before they wear out so even wear is not a concern. Also, with the little extra air pressure the front tires will run a little cooler and it should not effect the ride quality.

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Yet another tire pressure question.

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