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Old 04-19-2016, 12:02 PM   #1
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Interesting tire PSI discussion

I'm sitting at TCI Tire Center, and just overheard a conversation between two other Class A owners. One is a nice looking Rexhall on a F53 chassis, the other is a big Wanderlodge LXI (No it's bigger then my 40', but not sure if it is 45'.).

The gent with the Wanderlodge commented that he runs 115 PSI on the Drives/Tags, and 120 PSI on the Steers. Said he had bumped up the Steers to larger rims with 315/80's, and left the Drives/Tags at 12R's.

He said all of these PSI's were much higher then his weight indicated he needed to run with. But, he felt higher PSI's meant less sidewall flexing, and thus reduce possibility of sidewall cracking.

The other gent said he runs per the Manufacture of the Tire PSI charts + 5 PSI. Said he felt it gave him some contingency, and that he usually did not need to fuss with the PSI while on trips. And, that he knew his coach road better. (And yes, the F53 is not known for boulevard cruising ride as it is. And having had a F53 before, I understand doing all that you can to reduce front end harshness of ride!).

Why post this? Well, I was looking for opinions on if the Wanderlodge owner was correct in his opinion of less sidewall flex, and therefore reduced sidewall cracking?

Opinions?

And best to all,
Smitty
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Old 04-19-2016, 01:14 PM   #2
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Only thing that will stop Michelin sidewall cracking is don't buy them.
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Old 04-19-2016, 01:37 PM   #3
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The only reason I'd consider completely ignoring the manufacturers inflation pressures (as determined by the load on the tire) is if the recommended pressure is so low that it gives you a squirm instead of running a straight track in a crosswind or when passing a large truck. I increased my tag axle tire pressure about 15psi over recommended and still get a comfortable ride, but the rig tracks well. Tires at max inflation pressures give a very harsh ride.

I've been using Michelin's for over 11 years and do not have sidewall cracking issues, but I do not store the rig outside in the sun and run a lot more miles than probably 95% of RV'ers do. Our 2013 has 60,000 miles in 3 1/2 years.
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Old 04-19-2016, 02:44 PM   #4
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Got a fe minutes of idle time with the tire Laszlo the tire dude! (Meant as a complement, as he has been helping RV'ers for along time, and is well respected in the industry in general.)

His view was that the flex around when wheel area, which is designed to flex, would not be reduced much (if any) at all by bumping up PSI.

The Wanderlodge gent is gone now, and I never did get a chance to talk with him, as he was on a business call from the sound of it the majority of the time he was here.

So, while interesting to have heard his perspective. Think I'll stick with what Michelin and the tire pro's recommend. Oh, and when I told Laszlo that I ran about 10% over contingency, he said he saw no problem with that at all for how us RV'ers do our thing. (I assume of course, he also would have specially said to never go over the max pressure of the tire or rim!).

New shoes on now, and alignment in process. All I need now is for my fellow RV brothers and sisters to send money to the OnDRoad tire funds.... Ouch, even with FMCA prices, and only 6 out of 8 tires going on!

Best to all, travel safe, have fun,
Smitty
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Old 04-19-2016, 05:06 PM   #5
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There's a tire guru on another forum that advises to use the chart for the actual weight, then add 10%.
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Old 04-19-2016, 08:42 PM   #6
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LOL! Cracks on the sidewalls are not caused by flexing of the tire. Cracks are caused by the Sun, UV rays will cause what is called Sun Rot. If you do not cover your tires they will start cracking or checking between four and five years.

If the tires were built light for a softer ride which was the intention of the Michelin XRV tires for RV's, you will experience blow outs. They have improved that blow out problem in the last two years, but about five years ago it was head lines all the time on RV forums calling them zipper blow outs.
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Old 04-19-2016, 10:31 PM   #7
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Hey Smitty,
You know, once I weighed our coach, ready for travel, with both of us in it, I consulted the Michelin tire pressure guide, I found out what I was supposed to be running and, have ran those pressures (front and rear) and, have not added any 5 psi or 10 psi ever. Our coach, the Itasca Horizon 36GD with the C-7 CAT, has been running down the road, true and straight, handling has been superb, no leaning, wandering, porposing, what so ever. There is no odd tire wear, no "rivering", no cracking on any of the side walls that so many of the Michelin owners report on here. I don't have even ONE crack, in all six tires. And mine are the XRVs.

We purchased the coach with 40K on the clock and, it's presently sporting 63K. Now, I will admit, it sits in its cave when not in use and that is a completely sealed garage, not a double-open-ended breezeway. So, it may be helping those Michelins to preserve themselves by keeping any form of the elements off of them when the coach is not being used.

Yep, I feel for ya on the price of these darn tires. I may "stretch" the 7 year plan for mine since they're in such fine shape. The DOT dates are 3410 for all six of them so, I've got a while yet. Anyway, take care partner.
Scott
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Old 04-20-2016, 01:23 AM   #8
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I'll throw out my two cents. Tires are made to be driven and the rolling and flexing would cause the oils to do what they're suppose to do, keep the rubber supple. A reason to run the tires over the suggested PSI is to make the run cooler.

I sold tires for many years and I'm a nut about watching and maintaining my tires. Whne I bought my Dutch Star new, it had 120 PSI in the front tires and road to rough for my liking. After weighing it, I settled on 110 PSI. After a short time I could see the tires were wearing (underinflated). I added another 5 PSI and they are wearing like they should.

Tires adjustment can be pretty critical and at the price of them, it's worth paying attention.

Side Note:.....Tires prices went through the roof when oil hit a $100.00 a barrel several years ago. The manufactures blamed the cost of oil on the 50%-75% price increase, often $200.00 more per tire. I looked in my new tires and didn't see a whole barrel of oil floating in there. Funny thing, now at $30.00 a barrel, tires haven't come down at all in price?????
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Old 04-20-2016, 01:33 AM   #9
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Quote:
Originally Posted by RayChez1 View Post
LOL! Cracks on the sidewalls are not caused by flexing of the tire. Cracks are caused by the Sun, UV rays will cause what is called Sun Rot. If you do not cover your tires they will start cracking or checking between four and five years.
On our Dutch Star I never covered the tires, they went 8 years before cracking (and then only right around the lettering) became evident.
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Old 04-20-2016, 01:35 AM   #10
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Originally Posted by Dutch Star Don View Post
Side Note:.....Tires prices went through the roof when oil hit a $100.00 a barrel several years ago. The manufactures blamed the cost of oil on the 50%-75% price increase, often $200.00 more per tire. I looked in my new tires and didn't see a whole barrel of oil floating in there. Funny thing, now at $30.00 a barrel, tires haven't come down at all in price?????
Strange isn't it!
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Old 04-20-2016, 06:37 AM   #11
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Strange isn't it!

Not so much. The big increases were due to the tariffs imposed by the current administration on imported truck tires from China. (2009).

USA manufacturers were therefore able to increase the prices on their domestically produced products.

It is all about preserving the profit margins.

The lower oil prices are just icing on the cake for the manufacturers IMHO.
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Old 04-20-2016, 11:24 AM   #12
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I probably should have posted a 'Sorry!' up front, as I've been in 'tire mode' it seems for almost a year now! The 'Sorry!' was for posting another thread on tire PSI!

It was just interesting to hear his perspective, and the other guy was saying comments like 'I can see that.' or 'Well that seems logical.'.

Appreciate the confirmation that the Wanderlodge Gent's opinions were not necessarily sound!

Our new shoes are on, and I'll be tweaking the PSI until I feel they're where I want them. (As mentioned, I start with the weight to manufacturers PSI number, add 10% to this, and usually round up to the next '0' or '5' number, for ease of remembering. I then go drive the coach for several hundred miles, and look for signs of wear concerns. (I used the chalking method on our Bounder with GY G670's, and Laszlo asked me if I had ever heard of that yesterday as we were shooting the breeze.). I'll spend a bit more time on this go around, due to the tire sizes going to 295/80 from 12R's.

Anyways, best to all. Keep your PSI's within range, exercise frequently, cover and or use UV protection (My tires have Aerospace 303 on them.), keep your TPMS set properly - then go have some fun!!!
Smitty
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Old 04-20-2016, 05:40 PM   #13
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more than confused about tire pressure

So, need some help and seems there's a lot of folks with some great and I'll admit confusing input so I'm hoping I came to the right place!! I have a 38F Fleetwood pusher that has the Michelin, no boo's please, XZE2+ 275/70 R22.5's that are just over a year old. The Michelin chart says the maximum tire load single psi should be 130 and for dual 120. Suggestions on what to run them at then?

I'm certain there's going to be more than a few opinions on the subject but based upon what I'm reading the guy who I bought the RV from was obviously full of it.. He ran them at 95 PSI!! I took them to 105 but sounds like that might not be right. Look forward to the input even if I need to be taken out behind the shed. Only way to learn sometimes.

Thx.
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Old 04-20-2016, 07:18 PM   #14
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SWADoug-

Setting proper tire pressures begins with a four-corner weighing of your coach, as it will be loaded for travel/use. Have you done that, and if so, what were the results?
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