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Old 01-02-2016, 09:29 AM   #85
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Quote:
Originally Posted by Tireman9 View Post
Very interesting. If a tire is specified under US standards it would have a P or LT prefix and if Extra Load P type would have the words Extra Load and letters XL molded on sidewall as part of the size designation.
XL is a US designation not European.

In Europe they have passenger tires and "commercial" tires. The Commercial being similar to our light truck tires. There is no XL designation recognized by ETRTO (European version of the US Tire & Rim Association.

According to DOT regulations a tire must meet either TRA or ETRTO to be legal for sale and use on US highways. A tire company may not pick and choose parts of the different regulations and be in compliance with DOT regulations.

If your tire has no P or LT in front of the "235/70R15" characters and has no XL after the "235/70R15" then it would be a European Commercial tire intended for use on trailers or trucks and would have no de-rating.

If it has "XL molded after the tire size then it would be not in compliance with Federal Regulations which require a tire MFG to specify which standards the tire is to be tested under.

It would clear this whole topic up if you could post pictures of the complete tire size, and the actual load and inflation information molded on the sidewall.

A Load Index of 109 is the single load on a TRA LT235/70R15 LR-D tire according to TRA
I do not see an XL version of a P235/70R15 in the 2010 TRA standards book I am looking at right now.
Checking my copy of ETRTO I find a passenger 235/70R15 in both "Standard" load 36 psi max and "Reinforced" rated for 42 psi. These had Load Index of 103 & 107.
There is of course no "XL" in European standards.
In the Commercial section of ETRTO standards I do find a 225/70R15C (not a typo no 235) with a Load Index of 109 at 375 Kpa (54 psi)

So I have no Idea what you were told when you bought the tires.
Thanks for your input on this.

I wasn't told anything. I'm merely sharing information from Tire Rack's website. Have a look at the tire specs tab. You'll see there are no "P" tires listed for either tire line I mentioned.

Michelin Defender LTX M/S

Goodyear Wrangler All-Terrain Adventure with Kevlar

This is the tire I'm specifically speaking of-
Michelin Defender LTX M/S 235/75/15 109T XL
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Old 01-02-2016, 10:15 AM   #86
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While the tire captioned above

http://www.tirerack.com/tires/tires....WLXL&tab=Sizes

shows a rating of 2,271 pounds at 50 psi and the 30' International Airstream trailers have axles rated 4,500 pounds per the 2015 Parts Manual, any derating required by

*********************************
49 CFR 571.110
Tire selection and rims and motor home/recreation vehicle trailer load carrying capacity information for motor vehicles with a GVWR of 4,536 kilograms (10,000 pounds) or less.

S4.2.2.1
Except as provided in S4.2.2.2, the sum of the maximum load ratings of the tires fitted to an axle shall not be less than the GAWR of the axle system as specified on the vehicle's certification label required by 49 CFR part 567. If the certification label shows more than one GAWR for the axle system, the sum shall be not less than the GAWR corresponding to the size designation of the tires fitted to the axle.

S4.2.2.2
When passenger car tires are installed on an MPV, truck, bus, or trailer, each tire's load rating is reduced by dividing it by 1.10 before determining, under S4.2.2.1, the sum of the maximum load ratings of the tires fitted to an axle.

S4.2.2.3
(a) For vehicles, except trailers with no designated seating positions, equipped with passenger car tires, the vehicle normal load on the tire shall be no greater than 94 percent of the derated load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire.
(b) For vehicles, except trailers with no designated seating positions, equipped with LT tires, the vehicle normal load on the tire shall be no greater than 94 percent of the load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire.
****************************

would mean the weak link in the suspension is the tire. The tire would be under rated for the load.

Legal implications of that fact could be interesting in the event of an issue of damage to the trailer from tire failure or an accident involving others.

The sue happy lawyers are out there looking for business.

I think that tire load rating would be workable for the 3,800 pound rated axles used on 25' to 28' Airstream models.
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Old 01-02-2016, 11:15 AM   #87
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The new Michelin Defender LTX M/S 235/75/15 109T XL is a "Euro-metric" sized tire, not the "P" designation tire it replaced. None of the new Michelin Defender LTX M/S tires are "P" tires. Kind of strange to me, but I guess this is a new trend in tires. GoodYear Wrangler All Terrain Adventure tires are designated the same way.

From Tire Rack-
"If there isn't a letter preceding the three-digit numeric portion of a tire size, it signifies the tire is a "Metric" size (also called "Euro-metric" because these sizes originated in Europe). While Metric tire sizes are primarily used on European cars, they are also used on vans and sport utility vehicles. Euro-metric sizes are dimensionally equivalent to P-metric sizes, but typically differ subtly in load carrying capabilities."

I'm not sure what difference it makes, but the absence of the "P" on the sidewall may make a few Airstreamers a bit more comfortable using this tire.
Oops. I messed the aspect ratio up. 75 not 70.
Sorry
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Old 01-02-2016, 01:55 PM   #88
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There is some interesting information coming up. IMO as I stated in my blog post of March 2 the selection of the name "LTX" for a line of tires that appears intended for use of SUV and other "multi-purpose vehicles" but they do not seem to be providing sufficient information to the potential customers.

There are some tires in the LTX design that are clearly Passenger tires as they carry the "P" letter prefix. There are also others that are clearly Light Truck tires as they carry the "LT" letter prefix and now they are introducing "Euro-Metric" design tires that appear to be intended for passenger car use and not commercial use as they do not carry the "C" suffix after the rim diameter.

Compounding the confusion is the information from Tire Rack web page that may or may not be 100% accurate. There is also the potential of confusion of the de-rating of the tire load capacity when the tire is used on multi-purpose vehicles & trailers.

My primary technical contact at Tire Rack retired this past summer so I need to develop a working relationship with a technical resource at Tire Rack. I also need to contact the technical dept at Michelin as there may be some confusion between ETRTO standards and DOT regulations.

I am hoping to get a clear understanding of the inflation, speed and load limits for the different type tires in the Michelin LTX line. I would strongly urge that purchase decisions be held up untill there is a document issued by Michelin on the three different type LTX tires when used in RV service.
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Old 01-02-2016, 07:43 PM   #89
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Quote:
Originally Posted by franklyfrank View Post
LT means Light Truck, LTX designates Light Truck Extra load.
I have these Michelins on my 30' International 15" LTX - 108T high speed. They are awesome tires. At 50 PSI they are rated for 2,150 lb.
I can cruise at 70 MPH and not have any anxiety about trailer tires separating.
Hardly ever have to add air like with the crapola Goodyear Marathons AS installs on these expensive trailers.
ARRGGG!! All these letters and numbers are making my head swim. I'm having a little trouble keeping things straight. We need an "dizzy" emoticon. Maybe this one.

Frank, if you don't mind me asking, which Michelin's are you using currently?

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Old 01-03-2016, 07:34 AM   #90
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Allow me to second Tireman9's comment about the confusing use of letters in the names of some Michelin's tires. But they are not alone. Other tire manufacturers use the letters "LT" on some tire lines where there are P type tires in the mix.

The key to all this is separating the name of the tire from the size. Like the Ford Galaxy, or the Chevy Impala, a Goodstone Fire Eagle isn't about fire or birds - and that applies to the letters as well.
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Old 01-03-2016, 10:20 AM   #91
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Quote:
Originally Posted by Jim & Susan View Post
ARRGGG!! All these letters and numbers are making my head swim. I'm having a little trouble keeping things straight. We need an "dizzy" emoticon. Maybe this one.

Frank, if you don't mind me asking, which Michelin's are you using currently?

Jim
Jim I am using the tire I referenced above. Michelin LTX MS/2 108-T.
These tires are great! I did my research as well. The AS 30' GVW is 8,800 lb. The most I was ever load this trailer to was 7,800 lb. we mostly cruise at 7,000 lb and that is with the water tank full. Well withing the capacity of the tires.
What I have found on these forums is that people have a tendency to over analyse issues and as they say over analysis induces paralysis. BTW Tire Racks web page is the most confusing of them all. You want to research Michelin go on their website and , what I did stopped in at the dealer afterwards and got the straight story. The 108-T is the Speed rating on the Michelin. I run Michelin's all the way around, truck and trailer. I had a major tire separation last year with one of the Good Year garbage tires. $ 9,300 damage to the trailer, two trips to AS in Jackson Center it was nightmare. Henceforth I will only run Michelins period!
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Old 01-03-2016, 10:23 AM   #92
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Jim I am using the tire I referenced above. Michelin LTX MS/2 108-T.
These tires are great! I did my research as well. The AS 30' GVW is 8,800 lb. The most I was ever load this trailer to was 7,800 lb. we mostly cruise at 7,000 lb and that is with the water tank full. Well withing the capacity of the tires.
What I have found on these forums is that people have a tendency to over analyse issues and as they say over analysis induces paralysis. BTW Tire Racks web page is the most confusing of them all. You want to research Michelin go on their website and , what I did stopped in at the dealer afterwards and got the straight story. The 108-T is the Speed rating on the Michelin. I run Michelin's all the way around, truck and trailer. I had a major tire separation last year with one of the Good Year garbage tires. $ 9,300 damage to the trailer, two trips to AS in Jackson Center it was nightmare. Henceforth I will only run Michelins period!
PS: I have the original 15" wheels and the tires fit nicely on the trailer. They have to order them in because no one stock these in 15
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Old 01-03-2016, 11:46 AM   #93
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Michelin Defender LTX M/S 235/75-15 109T XL

Quote:
Originally Posted by Tireman9 View Post
I would strongly urge that purchase decisions be held up untill there is a document issued by Michelin on the three different type LTX tires when used in RV service.
The particular tire we started this thread about won't be available until March 2016, per Michelin. Hopefully, they will publish a full set of specs by then which will either compliment or correct Tire Rack's early publication.

Meanwhile, we're pleased to hear from those who've already had great results on Michelin's existing 15" tire with a 108-T rating on trailers that don't exceed those de-rated specs. It appears the new 109-T would just handle a bit more load, per the rating.
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Old 01-03-2016, 02:15 PM   #94
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Quote:
Originally Posted by franklyfrank View Post
Jim I am using the tire I referenced above. Michelin LTX MS/2 108-T.
These tires are great! I did my research as well. The AS 30' GVW is 8,800 lb. The most I was ever load this trailer to was 7,800 lb. we mostly cruise at 7,000 lb and that is with the water tank full. Well withing the capacity of the tires.
What I have found on these forums is that people have a tendency to over analyse issues and as they say over analysis induces paralysis. BTW Tire Racks web page is the most confusing of them all. You want to research Michelin go on their website and , what I did stopped in at the dealer afterwards and got the straight story. The 108-T is the Speed rating on the Michelin. I run Michelin's all the way around, truck and trailer. I had a major tire separation last year with one of the Good Year garbage tires. $ 9,300 damage to the trailer, two trips to AS in Jackson Center it was nightmare. Henceforth I will only run Michelins period!
Thanks Frank. I couldn't agree more, over analysis seems to be a real issue when it come to "trailer" tires, regardless of what letters precede or follow the name/size/whatever. The tires I have now are Maxxis and I've had no issues with them, however, it's time to replace them, and I want to step up to a Michelin, and maybe get ahead of a potential problem in the near future. I've never had a problem with the Michelin brand on any car/truck I've ever owned. Just to be fair, I've never had any tire "fail" outright.

There is much negative discussion here (and elsewhere on the internet) about "trailer" tires. The only conclusion I can draw from this is that "trailer" tires are simply poorly designed and built (respects, please, to tireman9 and capriracer, I mean no disrespect whatsoever, gents).

The point to all of this is to move on to a different scenario. A well respected company with a long track record of quality, Michelin.

OK, boys and girls, I'm off my soapbox now. Thanks again, Frank.

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Old 01-03-2016, 02:37 PM   #95
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So my Maxxis 225/75/15 tires with no prefix or suffix is a European rated light truck or trailer tire. Ten ply rated according to the Maxxis web site.
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Old 01-03-2016, 02:42 PM   #96
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Correction. In another part of their website they do use th ST prefix. My fault
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Old 01-03-2016, 02:44 PM   #97
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The level of confusion in this thread could indicate that some marketing types have succeeded in their efforts to "pull the wool" over the eyes of the consumer.

Using tire size & type nomenclature as part of a tire design name on tires where the type tire is not really of the type implied IMO has little advantages and clearly, intentionally? has disadvantages.

Another bit of confusion comes from the short hand nomenclature some posters use when describing the tire they are talking about i.e. discussing a tire as a 108-T.

Unless a reader of this thread has read and understood all 90+ posts there could easily be some confusion. De-rating of tire load capacity when applied to trailer or multi-purpose vehicles such as SUV or pickups applies to passenger tires. Since this de-rating is part of DOT regulations it does not matter where a tire is designed or made but that it is sold for use on US highways.
The Michelin Defender LTX M/S 235/75/15 109T XL is clearly a passenger type tire so it's load must be de-rated but there are tires with Service Description of 109 T that do not need their load capacity de-rated when applies to TT or SUV I just have to hope that everyone that reads this thread understands when load capacity needs to be de-rated.
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Old 01-03-2016, 03:03 PM   #98
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So what's the difference? I guess what I'm asking (maybe?) is what difference does it make? If the side-walls of the tire can handle the rough conditions of trailer towing, eg, like a LR C/D/E tire, what does it matter? I think I understand de-rating, but my camper is very light by modern standards (<4000 lbs), so weight shouldn't be an issue with the above captioned tires (I think).

Respectfully submitted, I much value your input here, tireman.

Jim
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