Bruce's Hypothesis of RV Tire Blowout

BrucePerens · 05-03-2017, 08:09 PM

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.

stormpeakco · 05-04-2017, 06:46 AM

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.

_____________________________________________
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).

**Bill** · 05-04-2017, 07:59 AM

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

**Larryjb** · 05-04-2017, 08:56 AM

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/

**wbmiller3** · 05-04-2017, 08:44 PM

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....

stormpeakco · 05-05-2017, 06:03 AM

Quote:

Originally Posted by Larryjb

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/

____________________________
Nice article, thanks.

Padgett · 05-05-2017, 10:08 PM

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.

scrubjaysnest · 05-06-2017, 07:44 AM

According to the tire folks I have talked with it's caused by the lack of use. This results it the oils in tire compound drying out which leads to cracking or tread peals. I like Bruce's idea better I think. When we had the TM we only had tire failures if we went over 4 years from the manufacture date.

**wbmiller3** · 05-07-2017, 08:54 PM

We've had three camping trips this year but nothing planned until the fall. I think I'll jack the trailer up in the garage to take the weight off the tires. Under the "it can't hurt and might help" rule.

Brittany Dogs · 05-14-2017, 09:36 AM

I like the "not used much" theory where trailer tires don't get used much and tend to get old then the oils dry out and the tire fails under the heat of travel.

I just replaced my tires this year and I'll give a short "ha ha" story. I ordered Marathons 225-75R15 D from my favorite local shop where I always get my car tires. I asked for the newest date code or I have a right of refusal. They came in at March 2016 and I said I'll call you back. Called another shop and they said they would only get the same tires from the same master distributor as my favorite shop. Called Mavis and they said they can order a Sept 2016 date code. So I went with that.

When I jacked up the TrailManor to take off the tires, which by the way, I have concluded that tires can only come off if you open the unit up and remove the skirts. At least on my unit that is. Anyway one side tire came off easy, the other side was very difficult. Every one of the lug nuts caused me to see stars and bust blood vessels. The impact wrench was unable to do the trick however I had a compressor that has a small reserve tank.

I go to Mavis and the tires they ordered were 205 in size. Thanks a lot guys you ordered the wrong tire. They said they fat-fingered the code. I left and called the first shop who still had my March 2016 tires. I was unhappy with the date code but heck, I have a trailer that is jacked up and needs tires. I get home with the new Marathons and lug on one of the tires just to see the side wall say "inflate to 50 psi" and the "ahh nuts" moment made me realize that first shop also ordered the wrong tires. I need load range D. They sold me LR C. Called them up and the jerk said you got C's because they no longer make D's. That was a lame attempt to just get me to go away. Needless to say I got rather firm worded with the guy, putting it nicely, and then said he found two LR-D tires for me at another store 150 miles away. It will take two days to get them in. I finally have the right tires after this ordeal. Not really a "ha ha" story but I did use 10 years worth of cuss words in one day.

The old tires that came off, after six seasons of camping, looked almost new. I only do 1000 miles a year. Tons of tread left but no way I was going to put a seventh season on them because I don't want to risk a blowout. The sidewall was in great shape too. It helps to keep the trailer in the garage when not in use.

Anyhow I never get six or seven years off of car tires which are exchanged every three or four years. So maybe that's why car tires rarely blow out.