Tire Pressure Help

[Andy Silven]

Ok everyone I'm lost and it seems that after talking to Michelin on the phone and even the Tire store I purchased my new tires from they wont give me the precise psi for the tire possibly due to liability. I have been told to put 120 psi front and back by the tire store I think that's to high and the Newmar coach label states 120 psi is max, so I'm running 110psi front and back. I have a 2003 Kountry Star 38' Diesel with Michelin Energy XZA2 Radials - 275/70R22.5 Michelin claims 85 psi front and back each tire by the weight I gave them but with out giving them exact weight of each tire?, I think that is to low and will cause damage to the tire or even a blow out. The coach is fully loaded with what we take on trips with a front weight of 9150 lbs and the back weight is 15,650 lbs, full take of deisel, 1/4 tank H2O, I'm unable to weigh each individual tire due to the way the state scale is set only front and back. Thank You so much in advance for any help.

Andy S
Oregon

[BattChief]

From the Michelin load table, they are telling you correct. Many will add 5 psi for a safety factor, but the maximum pressure will give you a harsh ride and poor driveability. Try Here for the michelin load table.

[GaryKD]

Hi,
We have the same tires and almost the same coach. I carry 90 PSI in the rear and am at 20K gross axle weight. The front is at 11.5K and I carry 100 PSI. This is with full fuel and water. Empty waste tanks. Propane is full.


Michelin says 85 PSI is the minimum regardless of low weight.

[Ricci]

Hi Andy - If you take the axle weight and add 5% to cover side to side variances you will be in pretty good shape. So front axle is 4803lbs. Use that off the chart for your tire type and size. Some add an extra 5% to the pressure figure as a safety margin. Repeat for the rear axle. I would not run under 90 pounds on a 120 lbs tire.

Tom

[jadatis]

Have put your given data in my made calculator.
First looked at this site of Michelin to determine the maximum loads single and dual of your tires.
Michelin RV Tires | View Michelin RV Tires load and inflation tables for motorhomes and recreational vehicles. | Michelin RV Tires
Single maxload 6940 lbs AT 130 psi !!!.
Dual maxload 6395 lbs At 120 psi .
So different At pressure for S and D.
Never seen it before but asumed it no error so yust filled that in.
But check it yourselfes on the sidewall, then you should find this difference.


Then the axleloads you gave, I asumed to be weighed fully loaded , so with persons and all the stuff in it as you go on trip( you gave fully loaded but all the persons in it?)
So if this is not the case , give what you added after weighing, and I will try to add that , but less accurate, and thats what why tiremaker and shop wont give an advice, you cant hold me responcible either.

Front 9150 lbs +10% added gives advice pressure of 93 psi so make it 95 psi. with this pressure a combined overload and unequal load R/L possible of 900 lbs before damage to most loaded tire on the front axle.
Rear 15650 lbs +10% added gives advice pressure of 79 psi so make it 80 psi. With this pressure a combined over and unequal load of 1545 lbs possible before damage to heavyest tirepair.

This if all is 100% acurate given and measured, wich is never possible.

Hope you now realise why most wont give an advice , its because of the responcibility that they have when someone goes over this loads or uses higher speeds .

I am save here in Holland , its much more difficult for you to sew me.

[Craig36]

For what its worth, the sticker behind the drivers seat in my 2007 KSDP 3910 says 120 PSI front and 95 PSI in the rear. I called Newmar, and was told that is what they recommend with the Michelin tires that came on the rig.

I am sure if you weighed your wheels as suggested, it would vary some... but I think the factory spec is a good compromise.

[D Lindy]

The only way to TRULY get the required tire PSI is to weigh the coach, and then look at the tire makers inflation chart. All these stickers on this coach and that all show the max pressure for the tires. GET IT WEIGHED. FWIF you'd get better responses postine the the Motor Home general thread. A lot of coach's come with Michelins not just Newmars.

[MTK46]

It's very interesting that what Monaco says to inflate the tires to is what mine should be after I weighted it. Has Bridgestones on it now & I have Toyos coming. Both charts show the same for my weight. 110 on front 100 on duals & 90 psi on tag.