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Old 07-09-2014, 06:52 PM   #1
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A little tire pressure help please

After a very rough ride on some roads I got my rig weighed at the Flying J. The weights are 7200 front and 15200 rear. The rig is set up with water etc as we are headed out to Yellowstone for a multi month trip so it is loaded. I looked at the Michelin RV tire chart for my tires--- 255/80R/22.5 XRV. The chart says I can/should run 70 in the front and 8o rear. I have been running 95 all the way around.
The chart weights seem very low but....., it is the chart. What do y'all think of running 80 in the front and 85 in the rears.
Many thanks!
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Old 07-09-2014, 07:13 PM   #2
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A good start

I run my Michelins 5psi over what the chart said and it's worked well for 3 years.

115 in front and 100 in all 4 rears.
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Old 07-09-2014, 07:24 PM   #3
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Go with the chart. Don't second guess the experts.


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Old 07-09-2014, 07:55 PM   #4
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Originally Posted by Muddypaws View Post
I run my Michelins 5psi over what the chart said and it's worked well for 3 years.

115 in front and 100 in all 4 rears.
X2, although our pressures are not as high...95 f and 85 r.
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Old 07-09-2014, 09:17 PM   #5
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The chart is for minimum pressure for a given load. Your left and right weights aren't likely to be the same. Try to find a place to get wheel position weights. Try a moving company. Once you have actual wheel position weights,use the chart and add 5 psi to overcome gauge inaccuracies. Regardless of the tire brand you have the Michelin RV site has a well written document on RV tire pressure and other good information.

Remember under inflation is the leading cause of tire failure. Personally, I run 10+ psi above the chart pressure.
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Old 07-09-2014, 09:28 PM   #6
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Originally Posted by EdB Wingman View Post
After a very rough ride on some roads I got my rig weighed at the Flying J. The weights are 7200 front and 15200 rear. The rig is set up with water etc as we are headed out to Yellowstone for a multi month trip so it is loaded. I looked at the Michelin RV tire chart for my tires--- 255/80R/22.5 XRV. The chart says I can/should run 70 in the front and 8o rear. I have been running 95 all the way around.
The chart weights seem very low but....., it is the chart. What do y'all think of running 80 in the front and 85 in the rears.
Many thanks!
Hi and welcome to the forum.

I like your caution in lowering the pressures and dropping to 85 all the way around and seeing what you think about the ride then makes sense to me.

Rick
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Old 07-09-2014, 09:41 PM   #7
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The best way to get a true reading on coach weights is to have a 4 corner weigh. Mine was done by Weigh to Go at an FMCA Rally.
My tires are new 3/13 through FMCA 295/80R22.5 Mine comes in at 94%(under) in the front and 106%(over) rear Total wt 12470lbs Front 21150lbs Rear and was told to run 105PSI Front and 100PSI Rear. My left rear is heavy but I think some of it is from the new Steel and Copper radiator or it may be the way the wife packs
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Old 07-09-2014, 10:36 PM   #8
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Go with chart +5. Your tires will wear better, be happier, and you'll see (feel) a substantial improvement in the ride.
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Old 07-10-2014, 03:57 AM   #9
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For these kind of situations I made my calculator.
Here a picture of your data filled in .
the tires I googled to be G load and found the maximum load to fill in.
Because 2 tires behind gave absurd high pressure advice , I asumed rear to be dual load so 4 tires on the axle.
then front 82 psi needed with all the reserves, and rear 95 psi. What where the pressures before? Probably even 110 psi.
Because you are sitting at front when driving , you experiŽnce the hard ride of the front axle , rear does not bump to my calculation, but your are not driving in rear seat. Edit: somehow got the idea that you had 95 psi all around , but reading back see you did not give used pressures before.

Here the picture, made with a formula that takes care ( better then the official European and sertainly better then American officially used ) that the deflection stays the same over the whole range of pressure /loadcapacity, wich is the goal of all the calculations. below the pressure advice some extra information that can be handy.
Also I add a reseve if weighed of 10% for things like pressure loss in time , unequall loading etc.

So this pressure , though low for front is sertainly save for your tires and no bumping. So keep the rear at 95 psi but you can savely lower the front to 82 psi with even some reserve.

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Old 07-10-2014, 05:03 AM   #10
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Quote:
Originally Posted by ImagineIF View Post
The chart is for minimum pressure for a given load. Your left and right weights aren't likely to be the same. Try to find a place to get wheel position weights. Try a moving company. Once you have actual wheel position weights,use the chart and add 5 psi to overcome gauge inaccuracies. Regardless of the tire brand you have the Michelin RV site has a well written document on RV tire pressure and other good information.

Remember under inflation is the leading cause of tire failure. Personally, I run 10+ psi above the chart pressure.
why wouldnt you use an accurate gauge? I find it funny to squawk about how important tire pressures are but the one device needed to accurately determine those pressures, youll suffice with "close enough".

Also to claim underinflation as the #1 cause of tire failure... wouldnt you need to know the exact tire pressures/load on every tire prior to failure? Another sweeping statement that has no merit.
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Old 07-10-2014, 07:49 AM   #11
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why wouldnt you use an accurate gauge? I find it funny to squawk about how important tire pressures are but the one device needed to accurately determine those pressures, youll suffice with "close enough".

Also to claim underinflation as the #1 cause of tire failure... wouldnt you need to know the exact tire pressures/load on every tire prior to failure? Another sweeping statement that has no merit.
Fact: Most high volume truck focused tire shops require tire gauges to be checked daily against their calibrated standard. How accurate is your gauge? I know you don't really care, but you asked. I use a Matco digital gauge and it was verified with a calibrated source.

Fact: Under inflation is the leading cause of tire failure according to tire manufactures.

Read my post again, if you can comprehend the message. If not, my message is don't run your tires under inflated. My " close enough" recommendation is to help avoid under inflation.

Your post isn't surprising. Most of your posts are done with attitude and seldom add information that helps the OP.
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Old 07-10-2014, 07:51 AM   #12
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Go with chart +5. Your tires will wear better, be happier, and you'll see (feel) a substantial improvement in the ride.
What he said ! GREAT job on getting it weighed ! Some people do not even go that far.
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Old 07-10-2014, 05:14 PM   #13
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Thanks for the opinions! I am new to this MH thing and have gotten lots of very good information. Have added a rear trak bar, done the CHF, and ordered the Roadmaster steering stabilizer. We had 5th wheels for years and I always checked the weights for the hauler and the 5th wheel. It made life a little easier knowing I was not overloaded. I am sure the lowered pressures will make a difference in the ride
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Old 07-11-2014, 07:50 AM   #14
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Quote:
Originally Posted by ImagineIF View Post
Fact: Most high volume truck focused tire shops require tire gauges to be checked daily against their calibrated standard. How accurate is your gauge? I know you don't really care, but you asked. I use a Matco digital gauge and it was verified with a calibrated source.
My tire gauges are accurate to 1/10th of 1 psi at 30/60/90/120/150 psi. Its not some some toy that gets tossed around.

Quote:
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Fact: Under inflation is the leading cause of tire failure according to tire manufactures.

Read my post again, if you can comprehend the message. If not, my message is don't run your tires under inflated. My " close enough" recommendation is to help avoid under inflation.

Your post isn't surprising. Most of your posts are done with attitude and seldom add information that helps the OP.
My posts most certainly have a contributing factor. I don't use fear or sweeping statements to make my points. When you say things like "add psi to compensate for gauge inaccuracies" well that certainly reads like "close enough" to me.
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