RV Tire Safety: “The tire failed because it is defective.” Maybe not…

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By Roger Marble
“The tire is defective.” I hear that statement quite often and will admit it is a bit of a “hot button” for me. For a good part of my 40 years as a tire design engineer I was tasked with doing forensic-level tire inspections and issuing “white paper” engineering summaries of the findings of the results of my inspection of tires that had failed. My inspection was not simply looking at the tire and saying “Yup, it failed.” I was expected to learn and identify the reason, the “root cause” for the failure, and to issue a report to management or even the auto company engineers.

In a number of cases the report could be as simple as: “The tire suffered a belt separation at x thousand miles. The separation initiated between the two steel belts on the serial side and progressed until the tire failed. The bead area showed signs of under-inflation/overload.” Or: “The tire suffered a Run Low Flex Failure which resulted in the melting of the polyester body cord” – as seen here:

Melted tire body cord

It would never be acceptable for me to say: “The tire failed so it obviously had a defect.”

I gave a short list of examples in my post of Sept. 20, 2015. Improvements cannot be made in tire production or in the manufacturing of any product if you only say: “There was some defect” – for without knowing and clearly identifying the actual defect, there is no way to know what material or process needs to be changed or improved to make the product better.

While simply saying the tire had a “defect” means you can’t be sure that simply replacing the tire with a new one or even a new tire from a different manufacturer will prevent a reoccurrence of another similar failure.

Tire failures come from a number of different root causes. Some have nothing to do with the tire itself. These can include wheels that are porous like this one:

Porous wheel

Other wheels can develop cracks so they leak air, or are even the wrong size as seen here. I have previously covered the variety of “failures” that involve leaking valves.  Many failures are from external causes, as seen in these examples.

Now, some may feel that because I worked in the tire industry I always want to blame the consumer, but this is not the case. In fact, I am personally responsible for one recall of more than 8,000 tires based on my inspection and research that identified the root cause for the failure was a tire plant manufacturing error due to an improper identification tag on a pallet of a specific rubber compound. Others had already seen the tires and decided they were “defective,” but they stopped there and did not make the effort needed to properly identify exactly what the “defect” was.

While I understand that consumers really are only interested in getting back on the road, if the reason for the failure was not something in the tire you can end up with another tire failure in your future.

If you have a failure and really care about the facts, I may be able to help. First you need to keep the tire if possible. Get good overall picture IN FULL SUNLIGHT. Also get some close-up pictures, close enough that you have no more than about 12″ of the tire in each shot. Email the pictures to me at tireman9(at)gmail.com and I will be happy to work with you so we might learn the real cause.

 

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

 ##RVT975

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Bill Massicotte
7 days ago

Thanks to you from all RV’ers for your knowwledge, expertise, and willingness to help.
We cannot ask for anything more!
Bill M.

Wayne
8 days ago

I found it interesting that the bead wire can stretch and break when a tire is mounted on an oversized wheel diameter. I would have guessed it to be tougher than that. Is it the stretching force from the air pressure or flexing of the wire that causes the wire to get hot and fail?
I have had very little tire trouble even using tires well past the recommended calendar age, and I attribute that to the information I have learned from your articles. Thanks

Roger Marble
8 days ago
Reply to  Wayne

Well first the bead wire is “High Tensile” so it doesn’t stretch before breaking. The force from inflation is way below the force needed to break bead wire unless you are talking 3 to 5 times the max tire inflation.
The slope of the wheel becomes a wedge and the side force applied by the tire mounting machine can be sufficient to break the bead wire but it is the “Wedge” effect that multiplies the forces.

It is also possible that in an effort to get the tire to “seat” that a person will increase tire pressure to many times the stated max inflation pressure. Many tires have a safety warning on the sidewall with a stated max pressure. NOTE this is not the pressure associated with the Max load.

Last edited 7 days ago by Roger Marble