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05-03-2017, 08:09 PM
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#1
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TrailManor Master
Join Date: Jan 2014
Posts: 893
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Bruce's Hypothesis of RV Tire Blowout
My hypothesis is that steel belted trailer tires fail through work hardening, a metallurgical phenomenon. The steel used is not supposed to work harden, but I think there's a case in which it does. During storage of an RV, the tires are left under load in one position for potentially months at a time. This causes plastic deformation in the steel belts. Then the tire is run, and with new flexing the crystal structure of the deformed steel accumulates strain. Repeated cycles of rest followed by use pin or tangle the crystal structure, which prevents it from flexing and thus hardens and embrittles it. The hardened, brittle steel then breaks as it goes through further flex-rest cycles, and we have a tire with internal breakage of the radial cords.
I suspect that a faster version of this phenomenon is also behind zipper rupture, which effects tires that have been run flat and can then rupture when inflated and kill or injure anyone nearby. Tire shops have developed safety processes for protecting their own operators from zipper rupture.
If this hypothesis matches the facts, we would see broken steel cords in blown tires. Tires with belts that do not work-harden might turn out to be more reliable - Kevlar or nylon, perhaps.
A possible way to avoid the failure mode would be to raise the RV to take the load off of the tires during storage, thus storing them with less deformation.
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05-04-2017, 06:46 AM
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#2
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Senior Member
Join Date: Jan 2015
Location: Colorful Colorado
Posts: 169
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Quote:
Originally Posted by BrucePerens
My hypothesis is that steel belted trailer tires fail through work hardening, a metallurgical phenomenon. The steel used is not supposed to work harden, but I think there's a case in which it does. During storage of an RV, the tires are left under load in one position for potentially months at a time. This causes plastic deformation in the steel belts. Then the tire is run, and with new flexing the crystal structure of the deformed steel accumulates strain. Repeated cycles of rest followed by use pin or tangle the crystal structure, which prevents it from flexing and thus hardens and embrittles it. The hardened, brittle steel then breaks as it goes through further flex-rest cycles, and we have a tire with internal breakage of the radial cords.
I suspect that a faster version of this phenomenon is also behind zipper rupture, which effects tires that have been run flat and can then rupture when inflated and kill or injure anyone nearby. Tire shops have developed safety processes for protecting their own operators from zipper rupture.
If this hypothesis matches the facts, we would see broken steel cords in blown tires. Tires with belts that do not work-harden might turn out to be more reliable - Kevlar or nylon, perhaps.
A possible way to avoid the failure mode would be to raise the RV to take the load off of the tires during storage, thus storing them with less deformation.
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Your theory seems plausible.
Wonder if setting for months in below freezing temperatures accelerates the process or just adds to the stress points.
Friends of ours in the frozen northland (Manitoba) have shown me photos of tire squaring during the winter...only takes a few days for them to acquire a flat portion to the load dependent portion and takes a few blocks of uncomfortable driving to round them back up...must reduce the longevity of the tires.
It seems logical to partially raise the leveling jacks, alleviate part of the load off the two tires on an empty and winterized TT (with some cardboard between the rubber and the concrete).
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05-04-2017, 07:59 AM
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#3
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Site Team
Join Date: Feb 2003
Location: The mountains of Scottsdale, AZ, and the beaches of Maine
Posts: 10,115
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Like many of us, I have accumulated far more tire failures on ST tires than on any other vehicle I have ever owned. I would love to know why, and I kinda like your theory. But let me add one data point to the contrary.
My wife and I spend half the year in Maine, and half in Arizona. While we are in Maine, we leave a 2005 Jeep Wrangler in the garage in Arizona (hot summer!) with weight on wheels. When we are in Arizona, we leave a 1998 Ford Ranger in the garage in Maine (cold winter!), again with weight on wheels. Neither of these vehicles has ever experienced a tire failure. Yes, the tires wear at the normal rate, but they don't fail, as in "come apart". Again, I admit that this is only one data point, but it seems a pretty good one.
As for squaring? We used to call it flat spotting, and I remember it happened a lot when I was kid. But I haven't seen it in a long time, including on the two vehicles mentioned above. I have been told (by a tire guy) that it happened on nylon tires, which were popular back then, but it does not happen on steel-belted tires.
Just my experience. But keep thinking, please. I would love to know why ST tires fail so much more often than P- or LT- tires.
Bill
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05-04-2017, 08:56 AM
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#4
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TrailManor Master
Join Date: Nov 2016
Location: Vancouver BC
Posts: 1,521
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This was very enlightening for me. The article also references differences between ST and LT tires. It makes some very good points against using LT tires on trailers.
https://rvingwithmarkpolk.com/2012/1...s-vs-lt-tires/
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05-04-2017, 08:44 PM
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#5
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Site Sponsor
Join Date: Oct 2004
Location: Southeast of Houston, Texas
Posts: 1,089
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One year when we didn't go camping for a long time I jacked the wheels off the ground when the trailer was in storage. With my tire failure average rate of 1 every 2 years, it was hard to tell if it made any difference....
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05-05-2017, 06:03 AM
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#6
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Senior Member
Join Date: Jan 2015
Location: Colorful Colorado
Posts: 169
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Quote:
Originally Posted by Larryjb
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Nice article, thanks.
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05-05-2017, 10:08 PM
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#7
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TrailManor Master
Join Date: Apr 2014
Location: Orlando
Posts: 2,796
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Suspect it is a combination of low tire pressure and storage. As long as the pressure is kept up (at least 50 psi for my LRDs) the belt should stay in the elastic range. A nylon cap will help also.
__________________
Looking for a 24/17 in or near Florida.
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