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Old 06-17-2011, 07:39 AM   #43
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110 PSI... Obvious the installer does not know much about RV's. Get the corner weights and check the OEM tire chart for the proper pressures.

Liquid balancing medium... When was the last time you looked inside a tire that had any form of liquid in it. It's a mess. I would hate to be the guy that has to change your flat and unmount the tire to repair it. Don't be surprised if you get a $25 charge to clean up the tire.

Lastly a 265 tire will be just shy of 1" taller so your speedo will be off by about 1.4 mph... 60 - 61.MPH. Also you tires are a tad over 1" wider... I hope you duals have the proper spacing and don't kiss each other when the flex. Did your installer tell you this?

Lastly each tire is about 5 lbs heavier. Also, consider the width of your rim... To narrow of a rim and to wide a tire could case some sidewall problems.
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Old 06-17-2011, 08:12 AM   #44
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I can't believe the installer is a Tire Enginner and knows that the Michelin tire sidewalls flex more than other tires and cause zipper flats. According to my friend who is a retired real tire engineer that flexing of the sidewalls is what you want to happen so the oils and chemicals move from inside the rubber to the outer laying of the tire to help stop cracking. The heating and flexing of a tire being driven cause what is called "blooming" which moves those oils and chemicals around. It is MHs that sit for a long time that don't get this flexing that have problems. Also you DO NOT get zipper flats from a tire inless it is damaged due to an outside source or a too low of an air pressure. I can tell he is a real expert by what he told you to inflate your tires to. You either need to inflate them to the label that is on the wall inside your MH (usually around the drivers seat) or get a tire specific Load and Inflation table and weigh your MH on a truck scale so you have the weight of each axle then look it up on the table. Even better is to get each tire weighed.
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Old 06-18-2011, 05:27 PM   #45
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You either need to inflate them to the label that is on the wall inside your MH (usually around the drivers seat) or get a tire specific Load and Inflation table and weigh your MH on a truck scale so you have the weight of each axle then look it up on the table. Even better is to get each tire weighed.
The only time the label inside your rig is correct is if you have the OEM tires and then only if you're loaded to the max AND loading is balanced. Otherwise use the load/pressure charts published by your tires manufacturer for that size and rating. Take the heaviest position on an axle and use that pressure on all tires on the axle.
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Old 06-18-2011, 05:39 PM   #46
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Please read my entire previous post again because that is what I told him. That label inside the MH is a lot better guidance than what the tire guy told him until he gets it weighed. If you haven't changed the size of the tires then that label is a safe inflation pressure.
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Old 06-18-2011, 07:55 PM   #47
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I can't believe the installer is a Tire Enginner and knows that the Michelin tire sidewalls flex more than other tires and cause zipper flats. According to my friend who is a retired real tire engineer that flexing of the sidewalls is what you want to happen so the oils and chemicals move from inside the rubber to the outer laying of the tire to help stop cracking. The heating and flexing of a tire being driven cause what is called "blooming" which moves those oils and chemicals around. It is MHs that sit for a long time that don't get this flexing that have problems. Also you DO NOT get zipper flats from a tire inless it is damaged due to an outside source or a too low of an air pressure. I can tell he is a real expert by what he told you to inflate your tires to. You either need to inflate them to the label that is on the wall inside your MH (usually around the drivers seat) or get a tire specific Load and Inflation table and weigh your MH on a truck scale so you have the weight of each axle then look it up on the table. Even better is to get each tire weighed.
I always get a laugh out of those that take the "tire guys" advice at a tire store. I guess they figure that working at a place for a few months makes them a better source of information then the engineers that design the tires and do the testing! The manufacturers web site and published manuals are the best source of information. Do some research on the web, especially the manufacturers site and published information.
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Old 06-18-2011, 07:59 PM   #48
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Please read my entire previous post again because that is what I told him. That label inside the MH is a lot better guidance than what the tire guy told him until he gets it weighed. If you haven't changed the size of the tires then that label is a safe inflation pressure.
I did read your entire post, that's why I answered as I did.
The posted pressure is only right IF the rig is loaded to the maximum GVWR and no other time. It is "safe" but not correct. The RV manufacturer has no idea how you will load your rig, all they can do is guess that it will be loaded to it's maximum GVWR.
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Old 06-18-2011, 08:34 PM   #49
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Quote:
Originally Posted by Mike Canter View Post
According to my friend who is a retired real tire engineer that flexing of the sidewalls is what you want to happen so the oils and chemicals move from inside the rubber to the outer laying of the tire to help stop cracking. The heating and flexing of a tire being driven cause what is called "blooming" which moves those oils and chemicals around..
Mike, Outstanding! I (check that - about 60 of us) got the same lecture from the Michelin tire rep at our rally in Myrtle Beach a couple of years ago.
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Old 06-19-2011, 01:13 AM   #50
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Originally Posted by Mr_D
I did read your entire post, that's why I answered as I did.
The posted pressure is only right IF the rig is loaded to the maximum GVWR and no other time. It is "safe" but not correct. The RV manufacturer has no idea how you will load your rig, all they can do is guess that it will be loaded to it's maximum GVWR.
Hi all,

I just posted my recent experience setting tire pressure on another thread, but it also seems relevant to current discussion. So, with apologies for the partial cross-post...

I spent a fair amount of time of telephone with RV manufacturer and tire manufacturer. Eventually, I got transferred to an engineer at the tire company. He was pretty surprised, as most "end-users" never make it to him. He told me that he was not supposed to answer questions regarding tire use from the general public, but he was reluctantly willing to hear me out on what I'd learned so far, and let me know whether I was barking up the wrong tree.

Basically, what you need to do is to weigh each side of each axle (2 axles for standard RV, 3 axles for tag-equipped, so you'll end up with either 4 or 6 measurements). Then, for each axle, take the higher of the two measurements, and double that to get the "axle-load", which you can find on your tire manufacturer's chart to calculate your optimal tire pressure. You may want to add some weight in anticipation on your next fuel stop or water fill, if either tank is mostly empty. Make sure to select the dual-tire pressure for the dual-axle tires!

After all that math, you'll be tired, so go to sleep! :-)

In the morning, before the tires warm up, and before driving on them, inflate (or deflate!) each tire to the calculated optimal pressure for the axle. Update your TPMS alert settings if you use one, and hit the road.

Never never never just take someone's word for your tire pressure, nor believe printed guidance that doesn't take your unique load, fuel level, water level etc. into account. It's usually not their home and family that are riding on them...

Safe travels!
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Old 06-19-2011, 03:03 PM   #51
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It's almost time to retire. I mean re-tire--I am retired.
I've got the original Michelin 235-80-22.5 tires, 7 years old, and other than moderate sidewall cracking, I've had no issues with these particular tires.
My replacement choices are Michelin again, or Bridgestone or Toyo. That's all I can find locally. The Michelins will run me $500 more than the Toyos and $200 more than the Bridgestones.
Now, cost is a factor, but not the only one. When I look at the tire specs for the size I need, the weights are quite different.
Michelin - 78.9 lb.
Toyo - 89.3 lb.
Bridgestone - 92.7 lb.
For 6 tires that is from 62.4 to 82.8 pounds total more than Michelins.
Has anyone else considered the weight difference in selecting new tires? Maybe 60-80 pounds isn't that big a deal, but still... And more unsprung weight adds to suspension wear and tear and maybe quality of ride.
I'm leaning to Michelin again just because of weight. I was going with Toyo until I did my research.
We had toyos and Good Years When we re tired we researched the whole gamut and elected to go with Bridgestone and Firestone Tires. Since then we have met several others who did same and all are quite pleased with the wear and the ride. And the price was the best we could find. JW
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Old 06-22-2011, 04:51 PM   #52
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I just picked up 4 235/80/22.5's at Sams Club yesterday. $1346.08 out the door. Then went to truck shop and had them mounted for $30.00 each.
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Old 06-22-2011, 04:52 PM   #53
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Forgot to say they were Michelin XRV's
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Old 06-22-2011, 06:58 PM   #54
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Hi all,

In the morning, before the tires warm up, and before driving on them, inflate (or deflate!) each tire to the calculated optimal pressure for the axle. Update your TPMS alert settings if you use one, and hit the road.

littlec
I'm not sure if it is the engineer stating the quote above, or your rendition. However, I still take exception to it. The tire manufacture charts will give you a range of pressures for different weights. As previously stated, 110 psi may not be the correct setting, but if it is the maximum tire pressure on the sidewall, then that is a pressure that can be set. If so, then, depending on altitude and temperature and the pressure is above 110 psi, it may be necessary to reduce pressure back to that setting. If however, the pressure falls to say to between 100 and 105, it may not be necessary to increase pressure IF the pressure that it reduced to are still withing the manufactures rating.

Using the following chart:

255/80R22.5 LRG XRV, XZE

--------70---75---80---85---90---95---100--105--110
Single 3875-4070-4300-4440-4620-4805-4975-5150-5205
Dual---7050-7410-7720-8080-8410-8820-9050-9370-9610

Single - 5205 at 110 PSI
Dual - - 4805 at 110 psi (using dual range divide by 2)

Let's assume that you have a steer axle at 9400 pounds, with 4700 pounds attributed to each wheel. Also remember that for every 1000 feet of altitude there will be a .48 psi change, and for every 10 degrees of temperature there will be a 2 percent change in PSI.

So, under the assumption of 9400 pounds:

Front Axle Wheel Wt. 4700 pounds each

PSI-- Wt.------Total--Diff--(-30)New PSI

95---4805--x2--9610---210---5.7----89.3
100--4975--x2--9950---550---6------94
105--5150--x2--10300--900---6.3----98.7
110--5205--x2--10410--1010--6.6----103.4

As you can see, if you were to put 95 psi in, you would be okay unless there was 30 degree drop in temperature, then you would be under inflated. With a pressure set at 100 psi, you would have 550 pounds of cushion, and with a 30 degree drop in temperature you would be at 94 psi, and still just under mfg specs.

So what I do is find a comfortable cushion, inflate to that PSI rating, and just forget about it. I do check my tires every time I start to move just to insure they are withing specs, but I don't have to inflate/deflate unless something drastic has happened.

Happy trails.
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Old 06-22-2011, 07:43 PM   #55
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You might be interested in this UV protector made for Michelin. It is interesting that it is the ONLY tire shine that is approved by Michelin. Mmmm they paid to have it made so they approve it. (lol) I bought two bottles of it at $7.99 a bottle which is not too bad. They tell you not to spray it on the tire but to spray it on a rag or sponge and wipe it onto the tire.

Michelin Wheel & Tire Care Products

I tried to buy some, they said all they had left was in kit containing stuff I didn't need/want. They had no idea if or when it would be produced again. Michelin used to say to use 303, then they came out with their own product (rebottled 303?) and 303 was no longer approved. Guess I'll use 303 since I can't get the approved stuff anymore.
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Old 06-23-2011, 10:55 AM   #56
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Regarding unsprung weight, consider holding a 5 pound weight at arms length and moving it up and down as fast as you can. Now change that to a 10 pound weight and try it. Your springs and shocks are having to deal with that same change in force and momentum, so it is harder on them.
That is what I thought you meant by "Unsprund weight"

Now consider this....

Take a pair of those octogon shapped end dumbells, 5 pounds , Put your hands on them and without moving them do some pushups.

now use 50 pounders and do the same thing

Any difference

The tires are not supposed to be going up and down, if they are properly balanced they remain on the ground at all times, not bounding like the weights in your analogy but sitting on the road. Like mine

The weight of the tire is a non-factor in suspension life.

Might affect MPG, oh about .0001 MPG I'd say.

What it will affect is tire heating, Tread life or other tire related things, it may also affect the ride (Be a bit stiffer) and handling.

However without a very serious cross sectional analysis of the tire (So I know where that extra weight is) and a whole bunch of research (So that I know what it means) I'd be hard pressed to comment on just what effect it has.
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