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Old 06-19-2012, 01:53 PM   #29
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Friday,

Responses to your comments:

* Are you replacing your tires every 5,000 to 12,000 miles? -- YES, we were before switching to 16-inch wheels & tires.

* NEVER going above 65 mph? -- YES, cruising speed is 55-60. Never drive above 65 mph.

* Replacing every 3-4 years? -- YES, previous ST tires failed every year or two (blowout and numerous tread separations).

* I don't know anyone that follows those 'rules', so you can't just pick out the 'inflate to maximum' all the time as gospel. -- YES, many people follow these "rules". Per the Airstream Tire Failure Poll, 40% of owners were running 65 psi (the max sidewall pressure for OEM, load range D tires) at the time their tires failed. Link to Airstream Tire Failure Poll: http://www.airforums.com/forums/f438...oll-76867.html

* Inflating to maximum makes no sense unless that happens to be where the capacity of your trailer meets the capacity of the tire. In your case, you've got a GVWR in the range of 4,500lbs, and tires with a load rating in the 5,400lb range together. Every tire/trailer combination is going to have a different percentage of capacity... so it would make sense that there is room to compensate with air pressure. -- It makes sense if you live in the desert southwest; perhaps not so much if you live in Canada. That extra 900 pounds of load capacity is the difference between a safe roadtrip and sitting on the side of the road waiting for a tow truck.

* My Sequoia tires are stamped 65psi max. Toyota recommends 30psi in the front and 34psi in the back... It weighs 2000lbs more than my trailer... -- Tow vehicles and cars are different from trailers. The weight of most tow vehicles does not usually approach the maximum load rating of the tires. We have load range E tires on our Tundra, which are rated at 80 psi, but we only inflate them to about 55 psi when towing, and less when not towing. I am sure the ratio of the actual vehicle weight versus tire load rating is much lower on your Sequoia than on your Airstream. For example, our Bambi is approximately 84%, while our Tundra is around 41%. That's why we run less than 80 psi in our Tundra tires, AND why we run 80 psi in our Bambi.

* Anyway... my Marathons have around 10,000km on them running 40psi... they gain 2-4psi hot. I'm good with that, but if you get more security from another spec, then do it... my trailer is also very light for a tandem axle... which is one of the reasons I really like the 22'. -- I believe your Airstream has 14-inch wheels with load range D tires that have 50 psi max stamped on the sidewalls. Thus your setup is very different from ours. Our Bambi has only one axle, so we don't have a second tire per side to run on when one of them blows out. Also, it was 113 degrees here yesterday and supposed to be hotter in the coming weeks; and our highways are littered with alligators from people running on under-inflated tires.

From your comments, it appears you are a skeptic that has not yet had a tire failure that damaged your Airstream and left you stranded. I wish you continued success with your setup. However, if you lived in Arizona, you would probably be a convert, too.
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Old 06-19-2012, 04:14 PM   #30
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Friday,

From your comments, it appears you are a skeptic that has not yet had a tire failure that damaged your Airstream and left you stranded. I wish you continued success with your setup. However, if you lived in Arizona, you would probably be a convert, too.
Not a skeptic, but if 40% of tire failures as reported in the poll still happened at max pressure... then pressure itself isn't the cure and might even be part of the problem in some cases, no?

Anyway, my bad, but I went out to look at my tires more closely, and they are "Duro" tires... not Marathons... So, add my name to the 'Marathons suck' list even though I don't have them.

If I lived in Arizona, I wouldn't be spending $7000 to repair all the leaks and water damage and could put that towards new wheel wells when they explode.

I'm sure the Airstream fairly will shoot one of my tires out soon enough, and you can say 'Told you so'... as everything else seems to have happened this year...
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Old 06-19-2012, 05:06 PM   #31
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2004 30ft slide just upgraded to 16" Michelin LT load range E tires at Airstream during Alumapalooza. Love the way the trailer rode and handled on the way home. Airstream inflated tires to 80psi. I have done My own research and think that pressure is to high. I am basing this on published Data I found. Michelin as well as other tire makers publish working radius data for the various tires. I didn't find this data for the Michelins until I had driven home. The radius of the tire was about .75 inches to great. This means I need to deflate the tires to match the given radius measurement for the load the trailer currently has. If I increase the load and the measurement decreases below the given data I would increase pressure. This method does away with the need to weigh the trailer and then find the psi on the load charts. Once You know the working radius data
just inflate or deflate the tire as needed for a given load to obtain the correct working radius.
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Old 06-19-2012, 05:50 PM   #32
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HUH? I would like to see that data. Jim
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Old 06-19-2012, 06:54 PM   #33
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Data varies per tire manufactures. I first found it for Marathons and found it for Michelin Rv(Motor Homes) Tires ,looked awhile to find it for the tires I have.
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Old 06-19-2012, 06:56 PM   #34
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Trying to upload pdf again.
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Old 06-20-2012, 02:25 AM   #35
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In a search of the Internet, it appears that "loaded radius" is a measurement related to tire deflection during dynamic testing. It is unclear whether this dimension is a measurement directly related to optimum tire loading; and it appears that the loaded radius could just be a reference for evaluating typical tire clearance for specific applications. If this is the case, it would be better to use the tire inflation charts instead of loaded radius dimensions, assuming one has decided to inflate tires to a value less than the maximum pressure printed on the sidewall.

Ctdair, could you please quote your source and text where a technical document states that the "loaded radius" of a tire should be measured and used as a reference to adjust tire inflation to match tire loading?

I am puzzled why one would deflate tires that were installed (and inflated to 80 psi) at the Airstream factory, and for which others have indicated that new Airstream tire placards indicate pressure to be 80 psi. The logic that drives owners to deflate tires escapes me, and perhaps it is time to sit on the side and await the details for new tire failures on the Airstream Tire Failure Poll. I encourage all who have tire failures to share their data on the link below:

http://www.airforums.com/forums/f438...oll-76867.html

Thanks,
Phoenix
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Old 06-20-2012, 04:22 AM   #36
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Searched for the original article can't find right now. Using the load /psi chart and knowing the weight carried by the axles ( all 4 tires on cat scale pad)
the psi chart shows 50 psi for my current tires , why run at 80 based on that?
Given the measurement I obtained at 80 psi It only can decrease as I release pressure to get down to 50 psi I am betting it will get to the loaded radius figure. Tires also publish revolution per mile, using the diameter It comes up under that number using the loaded radius comes up over. I will post measured height when I deflate to 50 as that is what the load chart shows.
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Old 06-20-2012, 04:47 AM   #37
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Ok just deflated tire and checked measurements. My height at 80psi was .25 high not .75 as originally stated. Bad memory. at 50 psi it is just about right on the money. These measurements are subjective as I don't have the exact center marked. Also just checked the cat scale tickets 7800# on the axles , so I fall in between the data on the chart 50 psi is just under but 55 is over by several hundred pounds. If i could determine the exact center reliably then I could inflate to say 51 or 52 psi and measure again. Hope that helps.
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Old 06-20-2012, 08:14 AM   #38
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Quote:
Originally Posted by Phoenix View Post
I am puzzled why one would deflate tires that were installed (and inflated to 80 psi) at the Airstream factory, and for which others have indicated that new Airstream tire placards indicate pressure to be 80 psi. The logic that drives owners to deflate tires escapes me, and perhaps it is time to sit on the side and await the details for new tire failures on the Airstream Tire Failure Poll. I encourage all who have tire failures to share their data on the link below:
Thanks,
Phoenix
Your puzzlement might be alleviated if you would accept the 1,000s of man years that the tire companies have put into testing and studying the physical properties of tire compared to the 1/2 hour it took Airstream's lawyer to write that statement that appears on the side of your trailer.

The inflation charts give a convenient means to inflate your tires so the proper Load Radius can be achieved without physically measuring the height.

I have been touting the use of Inflation Charts here for several years. I have to admit that I do not feel that many people have accepted the results of extensive testing history but all to many prefer to continue to drink the cool aid. The results of the testing conducted over the past 100 years is there in print for those who want to use it. I think that many prefer this approach because they are correct in the knowledge that under inflation will cause a blow out, thinking they will err on the high side for some false sense of security.

Yes in Jacks case he is very close to 80 psi for his rig but 80% or more of the rest are running down the road with overinflated tires.
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Old 06-20-2012, 08:30 AM   #39
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While I haven't weighed my Classic SO, I do have a pretty good handle on the weight of my camping gear, since I weighed my 27' Safari back in 2002. At that time it looked like we carried about 500 lbs. of camping gear, clothing, food etc. The trailer did not have any water in any of the holding tanks.

Fast forward to my Classic which was built before the higher capacity frames were implemented by Airstream. My maximum weight based on Airstream's ratings is 9,100 lbs. Based on the CCC rating which is on the label which takes into account water, propane and other options, I only have 555 lbs. of net cargo weight. I dare say I probably was pushing close to 9,100 lbs of weight. This is exactly why I upgraded to E rated tires which have a rating of 2,830 lbs at 80 psi. I feel fairly confident that I in no way exceeded the weight capacity of the tires. Technically the D's that were originally on the Classic still should have been able to carry the weight. The E's give me some reserve capacity over 2,540 which gave me some comfort level over the D's ratings.

Bottom line it looks a lot like the ST tires when dealing with high loads seem to break down faster than their LT counterparts. Failure of a Marathon D rated at the end of its 4 year life and now failure of the Maxxis E at the beginning of year 4. And to top this all off, I only carry this type of load once a year for about 220 miles. The return trip is always minus 60 gallons of water. I watch tire pressures like a hawk and my trailer is stored indoors. No UV issues here.


You have those dreaded ST tire blues. Your tires have tread separation. You are lucky you caught it before one of them blew and caused body damage. High pressure, low pressure, tight turns, it makes little difference. Hot weather and freeway driving means those puppies are going to blow. Maxxis' last longer than GYMs. Mine lasted three years before one of them blew in the middle of Navaho land.
Properly load rated LT tires are designed for hot weather and freeway driving. I switched to them and so should you.
Maxxis E's at 80 lbs and 1000 lb spring bars rattled my fillings and shook up my poor little Airstream. You and your trailer will notice a difference with LT tires and lower inflation pressures.
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Old 06-20-2012, 08:52 AM   #40
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Thanks for the info, jim
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Old 06-20-2012, 09:41 AM   #41
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Originally Posted by Phoenix View Post

I am puzzled why one would deflate tires that were installed (and inflated to 80 psi) at the Airstream factory, and for which others have indicated that new Airstream tire placards indicate pressure to be 80 psi.
It is easier to inflate to maximum than to determine the proper psi for every trailer. Tire shops and Airstream do not want to bother to do the work to look up tire weight capacities and compare with the GVWR of the trailer. That takes time and time is money.

They know underinflation is much worse than overinflation and therefore, CYA is the operative rule.

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Old 06-20-2012, 11:37 AM   #42
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I've just gotten off the phone with Airstream and their asking price is $368.95 per tire and wheel. $43.49 per wheel for shipping. The tires would arrive mounted and balanced. I'd probably sell my existing wheels either here on the forum or through E-Bay or Craigs list. I wouldn't try to sell the two remaining Maxxis tires that are on the rear axle unless someone felt that in lighter duty use, they would have a couple of years of life in them.

I'm still weighing the options of mail order pricing for the tires and wheels, then the cost of local balancing and mounting. Right now the difference in my time and effort and shipping charges might make the direct order from Airstream not that far out of line. Right now the low cost tire offer with free shipping is offset by the cost of shipping the wheels and then another $95 worth of local charges just to mount and balance the new tires.

Jack
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