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Old 12-10-2015, 11:51 AM   #113
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Originally Posted by Rocinante View Post
Hey, I just went out looking on the InterWebs for Michelin tire info and came across a new-to-me model, the Michelin Defender M/S 235/75R15 109T XL. I started a thread here so we can chat about it. Looks promising.

If you're already using this tire, please chime in. General thoughts also welcome, as always.
We have the Defenders on our '99 Sienna, been running them a couple of years now, no problems. I don't think I'd put them on a trailer unless there's an LT version.
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Old 12-10-2015, 12:51 PM   #114
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Whoops, Michelin customer service line just said the Michelin Defender M/S 235/75R15 109T XL won't be available until March 2016.

Rocinante is winterized / in storage and her GYMs still look good, so we should be able to wait for that model unless we're forced to do something with her tires before then.
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Old 12-10-2015, 02:17 PM   #115
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The safety factor came from some reasonable thought and with tongue planted firmly in cheek. As to the demand for low cost, not so. An AS is not a low rent acquisition.

Thanks for clarifying the design parameters for tires. Pat
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This promotional video is from Hankook but the process shown is basically what is in every tire made today (Michelin, Goodyear, Bridgestone, and even the "cheap" imports) follows.
Materials will vary but I think you can see that with the weakest part controlling the probability of failure it is impossible to use normal materials engineering and come up with a safety factor as one would with something made of metal like a bridge.

The "aging" rate of rubber is temperature variable with the rate doubling with every 10įC (18įF) increase in temperature so the rate is definitely not linear.. The temperature is the temperature of the rubber not just ambient. Running faster will increase the rubber temperature.
Hand held IR guns do not give the temp. of the critical interior structure of the tire so you can not predict.

Rubber crack and tear resistance changes with age and temperature. Older and hotter are worse. BUT age is not simply calendar age. A tire in the South may have same calendar age as one in North but the physical properties can be only half as good due to the accelerated aging.

I have covered Age in a number of posts on my home page web site blog.
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Old 12-10-2015, 02:26 PM   #116
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It would help if those posting tire size included all the letters and numbers that make up the complete tire size.

As I posted on Sept 11, 2011 in my blog on RV Tire Safety

"A quick review of some on-line RV forums show the problem of incomplete tire size information. Current posts mention:
225/75R-16E 235/80R 16s LT235/85R16E 225/75R/16E 235/80R16E 235/75R15 XL

None of these “sizes” provide what I consider the complete size nomenclature.
Here are some facts from the Tire & Rim Association industry standards book that point out why having all the information is both helpful and important.

P235/75R15 105S (Standard Load -35 psi @ max load)
2028# 35 psi 112mph on a Passenger car
1844# 35 psi 112mph on a SUV, TT or P/U (no Dual)

P235/75R15 XL 108R (XL = Extra Load)
2183# 41 psi 106 mph on passenger vehicle
1985# 41 psi on TT

LT235/75R15 101/104Q LRC
1985#single 1820# Dual 50 psi 99mph

LT235/75R15 LRC
1512#single 1377# Dual 50 psi 85mph

ST235/75R15 LRC
2340#single 2040# Dual 50 psi 65mph"
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Old 12-11-2015, 08:13 AM   #117
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"Andy - For the avoidance of doubt as they say, you are talking about this tire?

http://www.tirerack.com/tires/tires....TR5LTXMS2OWLXL"


Sorry I did not get back to this thread sooner. To answer your question, this is the tire we use on most Airstreams.

The Defender looks to be a slightly different tire, it weighs 2 pounds more on its spec. This can mean it is even more durable as there is more structure in it. Also though there is more unsprung weight though not very much.

Once they are available I will put a set on a high mileage unit to test but in the mean time it might be better to stay with the one that is proven.

Interesting we had a customer on the Newfoundland Caravan last summer. His Michelins were 4 or 5 years old on his 30' Classic with plenty of miles on them. He mentioned other tires were dropping like flies but not a problem with his.

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Old 12-11-2015, 08:44 AM   #118
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When I used my individual wheel scales, our 2014 Classic had one tire loaded at 1,921 pounds with the other three over 2,034 pounds for a total weight of 8,059 pounds supported by the four tires. In our application, the current 15" Michelin LTX (P) 235/75R15 XL tires that are sidewall rated at 2,183 pounds @ 50 psi but have to be derated to 1,985 pounds for trailer use would be overloaded.

The new model Michelin tire captioned above has a slightly higher load rating, but would still be maxed out on a two axle Classic. Both the old and new 15" Michelins would work fine on a tri-axle Classic.
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Old 12-11-2015, 08:50 AM   #119
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Originally Posted by Andrew T View Post
"Andy - For the avoidance of doubt as they say, you are talking about this tire?

http://www.tirerack.com/tires/tires....TR5LTXMS2OWLXL"


Sorry I did not get back to this thread sooner. To answer your question, this is the tire we use on most Airstreams.

The Defender looks to be a slightly different tire, it weighs 2 pounds more on its spec. This can mean it is even more durable as there is more structure in it. Also though there is more unsprung weight though not very much.

Once they are available I will put a set on a high mileage unit to test but in the mean time it might be better to stay with the one that is proven.

Interesting we had a customer on the Newfoundland Caravan last summer. His Michelins were 4 or 5 years old on his 30' Classic with plenty of miles on them. He mentioned other tires were dropping like flies but not a problem with his.

Andrew T
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I would be very careful is equating total tire weight to durability unless you have access to the actual tire build specification, which I doubt considering Michelin secrecy. Tire weight difference could simply be more tread for longer wear.
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Old 12-11-2015, 10:44 PM   #120
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I would be very careful is equating total tire weight to durability unless you have access to the actual tire build specification, which I doubt considering Michelin secrecy. Tire weight difference could simply be more tread for longer wear.
Allow me to second that. There is no correlation between tire weight and tire durability.
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Old 12-12-2015, 12:32 AM   #121
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Be that as it may, the previous Michelin tire is rated at 108T and the new Defender is rated at 109T. Don't know what that means for "durability", but it does mean the new Michelin Defender tire is rated to carry slightly more weight. Right?
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Old 12-12-2015, 06:25 AM   #122
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Be that as it may, the previous Michelin tire is rated at 108T and the new Defender is rated at 109T. Don't know what that means for "durability", but it does mean the new Michelin Defender tire is rated to carry slightly more weight. Right?

Sort of.

What's being encountered here is the difference between the American way of calculating load carrying capacity (ala The Tire and Rim Association - TRA) versus the European way (ala European Tyre and Rim Technical Organization - ETRTO). Not only is there a difference because of the measuring systems (English vs Metric), but there is a slight difference in the formula. For practical purposes, it isn't a difference at all. In other words, that alone does NOT have an effect on durability as the tire design would be the same in both cases.
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Old 12-12-2015, 06:33 AM   #123
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But the weight safety margin would be greater.
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Old 12-12-2015, 10:34 PM   #124
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US vs. European tire rating

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Originally Posted by CapriRacer View Post
Sort of.

What's being encountered here is the difference between the American way of calculating load carrying capacity (ala The Tire and Rim Association - TRA) versus the European way (ala European Tyre and Rim Technical Organization - ETRTO). Not only is there a difference because of the measuring systems (English vs Metric), but there is a slight difference in the formula. For practical purposes, it isn't a difference at all. In other words, that alone does NOT have an effect on durability as the tire design would be the same in both cases.
Interesting! So you are saying that for a given tire design, if the manufacturer labels it with a "P" they have to use the TRA formula and units, and if they label it without a "P" (or LT or ST) they have to use the ETRTO formula and units. AND they can come up with a different load rating, higher for an ETRTO tire?
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Old 12-12-2015, 11:45 PM   #125
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Another China Bomb!

Luckily, looks like that one is still "unexploded!" I'll tell you what happened....all ST tires are made in Asia now days. They are all JUNK! The best money that you will ever spend, if you are planning on towing, will be to replace all your ST tires with 16" LT tires, preferably USA made. Then if you run the max pressure listed on the sidewall, you will never have to worry about your trailer tires again. It's just that simple! Everyone tries to explain this with some "educated guess." Really, it's just not that hard. Look around at all the other "great" products we get from China..... lol.
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Old 12-13-2015, 06:07 AM   #126
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But the weight safety margin would be greater.
Not exactly. Remember the construction of the tire is exactly the same - so when the tire is applied to a vehicle, it doesn't matter what which standard was applied - the tire behaves the same.

Put a different way, when a tire is properly designed, the tire engineer can apply either standard and label the tire accordingly. It will pass the tests regardless.

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Interesting! So you are saying that for a given tire design, if the manufacturer labels it with a "P" they have to use the TRA formula and units, and if they label it without a "P" (or LT or ST) they have to use the ETRTO formula and units. AND they can come up with a different load rating, higher for an ETRTO tire?
Not exactly. LT and ST standards are TRA. ETRTO uses a "C" (for Commercial) after the numbers in place of LT and doesn't have an equivalent of an "ST" designation. Plus there is another standardizing organization JATMA (Japanese Automobile Tire Manufacturers Association) that also doesn't use the letters for passenger car type tires (and they have a third different formula).
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