15" ST Failure to 16" Replacement..a journey

[Silvertwinkie]

Jack has "E" rated tires, with the upgraded Classic rims, and is inflating them to the recommended and proper 80 psi.

I have "D" rated Maxxis tires and I inflate to the recommended 65psi. Now I could inflate to 60psi and still be well within load capacity, but what is the point? Then I would be by the book under inflated, even after the tires warmed up slightly during use.

If a manufacturer states inflate to 80psi, I doubt very seriously that they haven't taken into consideration on any tire put into service that it may increase a lb or two in pressure during use. Additionally, I would find it hard to understand how a tire manufacturer would state fill to a specific psi, and particularly on a trailer tire not understand the physics involved with the tires in pivoting turns.

As far as I am concerned, Jack has followed best practice in the inflation to 80psi. I would NOT recommend inflating much less than the psi he has been filling, mainly because his slide is gonna be close to 10k lbs in trailer weight and inflating to say 75lbs is gonna cut it really close. See attached Maxxis chart.

Now I do agree that since this is the second failure on the same axle, only this time both tires on the axle (and a different tire brand than the first failure), that perhaps the axle and/or hub(s) are having issues (out of alignment, etc) and that as the tire ages, the stresses become too much for them.

BTW Jack, I checked and Maxxis has a 5 year warranty on the tires FWIW.

I think that the 16" rim with the LT tires are not a bad move, but remember that you will prob need 5 rims and 5 tires since you have to get a spare....and as has been pointed out, any tire subjected to high stresses will eventually fail, possibly even the 16" LT tires.

My suggestion would be to make sure the hubs and axles are properly aligned and possibly add some centramatics to the mix. Either way though, sounds to me like new rubber across the board is unfortunately in your near future.

[HowieE]

What size tire and how many does he have? What is the running weight of the trailer? Really can't determine the correct pressure till we have that information.

[Silvertwinkie]

Looking at the chart I provided, he has ST225/75R15s like many of the wide body Airstream models have installed (up until recently-- I heard Airstream is putting 16"LT tires on trailers now---NOT VERIFIED).

Additionally, since its not a 19' Bambi or smaller and that he does not have a tri-axle 34 footer, we can safely say he has two axles, meaning 4 tires.

Looking at the Airstream site, his trailer has a wet weight of approx 9100lbs.

Filling his tires to 75PSI will give him 445lbs per tire extra capacity (1750lbs for all 4) beyond what he carries wet. @ the 80lbs he inflates to, he has 555lbs per tire extra (2200 for all 4).

Now keep in mind that many of the wide bodies starting after mid 2005 came with upgraded axles, and the 30' slide was then rated at 10,000lbs GVWR, which at 75lbs of pressure would leave only 333lbs of extra capacity per tire.

Now one could argue will a customer load a trailer utilizing every pound of the NCC?! Odds are probably not, but I know for a fact that the old numbers were somewhat conservative. For example, my hitch weight was higher that the specs, and my NCC being a 2004 was woefully low and very easily exceeded prior to Airstream upping the axles from 6000 to 7000, thereby increasing the GVWR from 6300 to 7300lbs. I would suspect other wide body Airstreams would be in a similar position of having a low NCC prior to the mid 2005 axle upgrades on all wide body trailers (including the 30' slide up until it was discontinued).

Bottom line, my vote would be to stay as close to 80psi as possible...79psi if it made folks less excited. If Jack didn't have the slide out, one of the heaviest Airstream trailers built, I might have different feelings on the subject, but he did mention he was fully loaded, so my guess is that he was at or maybe even slightly beyond the stated 9100lb GVWR. If he had a tri-axle 34 footer my thoughts might also be different since there are 6 tires, but he has two axles and a slide....a very heavy combo.

My vote is beside needing new tires at this point, that he have the axle checked for being within spec and possibly adding centramatics as well. I firmly do not believe his issue is with tire pressure as he has followed the manufacturers instructions on both sets of tires, and the only issue he seems to continue to have is on the one axle.

[Gene]

The tire pressure wars are engaged.

When you buy a car or truck the recommended pressures are on a sticker and they are always less than the maximum pressure on the tire. Maximum means maximum, not the proper pressure for the load.

Certainly low pressure is worse than high pressure, but every vehicle has a proper pressure for the load. I suggest using the tire tables and call the tire manufacturer and ask them what they think. Michelin does not recommend maximum pressure, but the pressure for the vehicle and load. Part of this can be a little guesswork too.

Tire stores and Airstream will put maximum pressure in if the tire is not the standard tire for the vehicle and they have no easy guidance from a sticker. Maybe it is because they don't have to look it up and time is money to them. Maybe they think it will avoid liability. When I had tires installed at JC, they put the maximum pressure in and then I let the excess out.

For our trailer I ran 68 lbs. in the Michelins, but found the edges were wearing a little faster and that indicates I needed more air, so I increased it to 72. These are for Load Range E tires.

For your Classic, Jack, you may need pretty close to maximum.

Gene

[jcanavera]

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.

[Friday]

Originally Posted by Phoenix

There are lots of conflicting opinions regarding proper pressure for trailer tires. Please see below, before deciding for yourself:

Discount Tire: Trailer Tire Facts - Discount Tire

Extracts from above link:

* Underinflation is the number one cause of trailer tire failure.

* Always inflate trailer tires to the maximum inflation indicated on the sidewall.

Costco recommendation is identical.


On our single axle, 19-foot Bambi, we run 80 psi in Michelin XPS Ribs (225/75x16 LT, load range E).

We had Goodyear Marathons (ST, load range D) and Maxxis (ST, load range E) tires both fail (blowouts and tread separation) before switching to Michelins about 1.5 years ago. Absolutely, no problems since then, in about 3-4,000 miles.

Are you replacing your tires every 5,000 to 12,000 miles? NEVER going above 65 mph? Replacing every 3-4 years?

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.

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.

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...

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'

[overlander63]

Originally Posted by Silvertwinkie

Looking at the chart I provided, he has ST225/75R15s like many of the wide body Airstream models have installed (up until recently-- I heard Airstream is putting 16"LT tires on trailers now---NOT VERIFIED).

Additionally, since its not a 19' Bambi or smaller and that he does not have a tri-axle 34 footer, we can safely say he has two axles, meaning 4 tires.

Looking at the Airstream site, his trailer has a wet weight of approx 9100lbs.

Filling his tires to 75PSI will give him 445lbs per tire extra capacity (1750lbs for all 4) beyond what he carries wet. @ the 80lbs he inflates to, he has 555lbs per tire extra (2200 for all 4).

Now keep in mind that many of the wide bodies starting after mid 2005 came with upgraded axles, and the 30' slide was then rated at 10,000lbs GVWR, which at 75lbs of pressure would leave only 333lbs of extra capacity per tire.

Now one could argue will a customer load a trailer utilizing every pound of the NCC?! Odds are probably not, but I know for a fact that the old numbers were somewhat conservative. For example, my hitch weight was higher that the specs, and my NCC being a 2004 was woefully low and very easily exceeded prior to Airstream upping the axles from 6000 to 7000, thereby increasing the GVWR from 6300 to 7300lbs. I would suspect other wide body Airstreams would be in a similar position of having a low NCC prior to the mid 2005 axle upgrades on all wide body trailers (including the 30' slide up until it was discontinued).

Bottom line, my vote would be to stay as close to 80psi as possible...79psi if it made folks less excited. If Jack didn't have the slide out, one of the heaviest Airstream trailers built, I might have different feelings on the subject, but he did mention he was fully loaded, so my guess is that he was at or maybe even slightly beyond the stated 9100lb GVWR. If he had a tri-axle 34 footer my thoughts might also be different since there are 6 tires, but he has two axles and a slide....a very heavy combo.

My vote is beside needing new tires at this point, that he have the axle checked for being within spec and possibly adding centramatics as well. I firmly do not believe his issue is with tire pressure as he has followed the manufacturers instructions on both sets of tires, and the only issue he seems to continue to have is on the one axle.

I just went out and walked the lot, and the only Airstream on the lot with Michelins is the Eddie Bauer. It has 16" load range E tires, and the pressure on the placard is 80psi.
The other Airstreams all had Marathons, and the recommended pressureis 65 for all load range D tires, and 50 for load range C tires. Yes, some of the smaller double axle Airstreams have 14" load range C tires. All specify the maximum for the load range.

[jcanavera]

I'm getting some tire quotes at this point for the Michelin LTX M/S 225/75R 16 E rated tires. Looks like the best I have found on the Internet is $792 plus $95 shipping. Michelin is offering a $70 rebate on the purchase of 4. Local Sams Club is selling for $229.88 each.

The Tredit site shows the T02 wheel with an offset of 0 degrees. Looks like I need the 16" wheel with the 6-5.5 bolt pattern. T02

Airstream is selling a wheel/tire package that can be shipped from their store. They are working me up a price and shipping cost at this time.

I'm looking at local pricing too. Local and state sales taxes run between 6.5 to 8.5%. It may cheaper to pay the taxes than the shipping.

Jack

[Phoenix]

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.

[Friday]

Originally Posted by Phoenix

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...

[ctdair]

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.

[xrvr]

HUH? I would like to see that data. Jim

[ctdair]

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.

[ctdair]

Trying to upload pdf again.

[Phoenix]

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

[ctdair]

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.

[ctdair]

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.

[HowieE]

Originally Posted by Phoenix

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.

[handn]

Originally Posted by jcanavera

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.

[xrvr]

Thanks for the info, jim