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Sunday, October 22, 2023

"Blowout" really Puncture, Runlow and Cutting impact

 This tire was presented as just a "Sudden Blowout" with a claim that the tire "must have been defective"

This is what the tire looked like when I got it.

We can see the severe damage to the tire tread area in picture #1

In the next two pictures we can see the puncture to the air chamber which allowed air to leak out.

Here we see the small nail from the inside.  
In picture #4  between the 2 arrows we see the "rutting" caused by the wheel flange digging into the lower side of the tire. This is evidence of many hundreds of miles run with significant loss of air.

In picture #5 we see the cut steel filaments. 
In the last picture we see more cut steel filaments. Note the lack of the "cup / cone" configuration normally found in steel that has failed from being cut by some external object and not from overload or stretching.

 My conclusion was that the tire was run while not properly inflated for many hundreds of miles due to the puncture and a lack of proper maintenance. 
This would lead to weakening of the tire structure. Hitting some sharp object. the weakened tire was cut and the tire suffered a fatal failure.

Sunday, October 15, 2023

Why you should not spin your tires. A forensic analysis

 I have mentioned a few times that toward the end of my career as a Tire design Engineer I became a specialist in failed tire inspection. In my RV tire seminars I have likened this work to what was shown in the TV series CSI.

I will be sharing the results of  a few of my inspections over the next few weeks and months but will start off with one of the more exciting types of tire failure. I was not involved with the tire seen in this video but it provides the evidence on why it is recommended that if your car or truck is stuck in mud or on ice you should not spin your tires. The video is just entertainment.

I believe this truck was part of some entertainment at some auto event but it shows what can happen when you exceed the speed capabilities of a tire. The wire in the tire bead that holds the tire on the wheel can fail at excessive speed.

Here are some pictures of a tire I did receive as part of my job.

This is what the tire looked like when I received it.


As you can see it looks

like the tire was "shattered".

This is very unusual as

normally tires fail from either 

a sidewall failure from being run low on air, or have a belt detachment due to long term overloading and excessive heat.

This picture shows the broken steel of the belts and does not show signs of a detachment between the belts.


When steel fails from tension the steel shows a narrowing of the filaments as easily seen in this shot of the tire bead wire. This is classical "Cup - Cone" tensile failure of steel

Here is what the bead wire looked like.

A close (microscopic) examination of the steel filaments shows the signature "Cup-Cone" shape as seen in this Electron Microscope comparison of tensile failure vs a cut filament as seen in the lower right.

This is one of the PowerPoint slides I use in my RV Tire seminars.

So the bottom line is that if you are stuck on mud or ice and your car or truck does not have "limited-Slip" differential if one tire stops and the other spins the spinning tire can easily exceed the high speed capability of the tire.

So do not "spin" your tire in an effort to get moving. I would also recommend against showing off at car shows.