Tuesday, July 5, 2022

MENU

RV Tire Safety: Simple question: Why do tires fail?

Why do tires fail? In reality, tires fail for a relatively small number of root cause reasons that can be discovered. However, it does require detailed and sometimes exhaustive investigation. By “root cause,” I mean the initiating feature or condition that eventually led to the failure. Too often people confuse the tire’s ending condition with the initiating or “root cause” reason for the tire to end up in the condition they are observing.

For the last few years of my 40-year career as a tire engineer, my primary job duty was to investigate failed tires that had conditions that were hard to understand or provided confusing and sometimes contradictory evidence as to the root cause for their condition. With that background, I have developed some guiding principles for the most likely reasons for tires to fail.

Most likely reasons for tires to fail, in no special order:

  1. External Damage. These include punctures, cuts, impacts, wheel and valve failures and similar conditions.
  2. Run Low Flex Failure. This is best described by the failure of the tire sidewall due to excessive flexing. The flexing is the result of operation when the tire is significantly under-inflated.
  3. Belt and Tread Separations. This is when the belts of a radial tire detach from the body or from each other and/or when the tread rubber detaches from the top belt.
  4. Manufacturing Defect. For the purpose of this discussion, this would be when components of a tire were not manufactured to intended specification.

The “why” for some of these are obvious, such as the External Damage category.
Others can be further traced to various contributory reasons.

Run Low Flex Failure is a more accurate description of what some incorrectly call “blowout.” When a tire loses significant inflation air, they flex much more than the body cord can tolerate. Excess heat is generated which can, in extreme cases, result in the polyester actually melting. I showed examples of what this can look like in THIS post. Polyester is used in most Passenger, ST-type and LT-type tires. Steel body tires are used on most Class A RVs, and the steel can fatigue. I covered “zipper” failures and steel fatigue in THIS post.

Belt and Tread Separations occur primarily because the rubber around the belt cords or between the belt rubber and the tread rubber isn’t strong enough. It can be weak for a variety of reasons. Some might be design, some might be manufacturing and some weakening can be caused by cumulative improper service conditions.

Tires made by a reputable company

Now let’s talk about tires made by a reputable company. That would be one that has tire stores and dealers with physical stores. Also, it sells tires that have a warranty of two or more years.

If this tire is subjected to thousands of miles of lower inflation or higher loading or operation at higher speeds or stored in full sunlight, it is reasonable to expect the strength of the belt and tread area rubber to lose a good portion of its strength primarily due to the increased operating temperature of the tire. If this tire is in service on a tandem axle trailer, then there is also increased Interply Shear, which can overload the belt area rubber. The combination of the above may result in a belt or tread separation.

Another possibility is a Manufacturing Defect. These usually occur in small numbers as tires are built in batches. So the substitution of the wrong type of rubber may cause tires to fail. It is important to understand that in almost all cases, this type of “defect” usually shows up at early life of the tire.

It is also very important to understand that, unlike some lawyers, engineers deal in facts and logic. Simply having a tire fail is not in itself proof of a defect. But, all too often, that is the position that those in the legal profession seem to jump to. That approach may result in a nice payout to the lawyer. However, it will not result in product improvement as there has been no determination or identification of the actual initiating “defect.”

Possibility of design weakness

Finally, there is the possibility of a design weakness. I do not believe that anyone is intentionally designing tires to fail. However, this sometimes may occur when the performance goals of the manufacturer are limited to meet the bare minimum for strength and durability and the focus is primarily on low cost. There is no absolute way to identify these tires. But I do believe there are indicators when looking for tires that are made to a higher standard of quality and durability.

I would consider a tire company reputable if it had a chain of stores across the country. If the tires carry the name of the manufacturer and have a multi-year warranty—the longer the better—then they probably have higher durability requirements than those established by DOT.

Maximum speed for tires

For ST-type tires, I would look for tires with a Speed Symbol of “L” (75 mph) or SLOWER. Now, a side point about speed. I did a POST some time ago focusing on speed, and strongly recommend you read it. I do not think I would recommend any tire for general use that does not have a speed rating molded on the sidewall. Few people realize that ST tire loading is based on the assumption of 65 mph Max operation speed.

I do hope this post will help some to have a better understanding of what can contribute to tire failure, and consider what you can do to lower the chances of having such a failure.

Have a tire question? Ask Roger on his new RV Tires Forum here. It’s hosted by RVtravel.com and moderated by Roger. He’ll be happy to help you.

Read more from Roger Marble on his blog at RVtiresafety.net or on RVtravel.com.

 ##RVT1049

Comments

Subscribe
Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

8 Comments
Newest
Oldest
Inline Feedbacks
View all comments
Bob Weinfurt
2 months ago

I bought an old class C seven years ago. At that time the tires were only as few years old. I’ve kept them covered while parked, properly inflated, and fortunately haven’t hit any thing on the road. They’re now eleven years old and still look like they did back then. If something happens to one of them, I’ll know it’s time to replace all of them.

John
2 months ago

We had 3 tires go bad, first a blowout. Next I noticed a vibration and it was tread separating (we got our spare put on before the blowout). Then another blowout. First was in Apr 2016, next in August 2019, then finally in Nov 2020. All 3 were in the same position on our Winnebago Aspect 26A. I believe it was heat from the engine exhaust pipe, which went from the centerline to the passenger side of the coach, at the very front of the rear wheel well. We have since had the exhaust line rerouted, now goes aft to just forward of our generator, and the new exhaust pipe is just beside our generator exhaust pipe. So far, so good.

Bob Weinfurt
2 months ago
Reply to  John

Good thing you saw that. It sure can cause a tire to run hot.

TIM MCRAE
2 months ago

I can’t agree that quality is guaranteed by nationwide branded dealerships.

Quality name brand tires, yes, but most if not all the name branded dealerships are franchises who supplement their high cost of ownership with over pricing and scam services. And you are limited in your tire brand choice.

I buy quality warranted name branded tires from national tire installation chains so I can get warranty, road hazard warranty, and free service in any city.

I have used all the big ones. Discount Tire was my go to for 30+ years but that has changed.

Honestly, Walmart is now my favorite for passenger cars and Toads.

I have not yet had to replace tires on a class C or A as I seem to upgrade before the tires age out!

So I am looking for recommendations on national truck tire service.

Thanks

TIM MCRAE
2 months ago

Thanks Roger! Good article.

However, Belt & Tread Separation are symptoms not causes.

They are the result of improper inflation, loading, manufacturing or design, and road hazard.

wanderer
2 months ago

Don’t understand this part.
“I would consider a tire company reputable if it had a chain of stores across the country.”
I know of only one company (Firestone) that has a chain of stores. If there are others which we don’t realize are owned by a tire company, please fill us in.

TIM MCRAE
2 months ago
Reply to  wanderer

Goodyear

Gary Broughton
2 months ago

In 45 years we only had 2 flats and they were road debris.
I didn’t go by the 5 or 7 year tire replacement. If they looked bad and needed changed we changed. I’d have 40,000 or more miles on them. And I kept a good spare.
We had 2 friends that had tire problems all the time, one had 3 flats on one trip. They never checked their tires for air or damage.
You hit potholes, debris, curb’s and don’t look back at your tires.

Sign up for our newsletter

Every Saturday and Sunday morning. Serving RVers for more than 20 years.