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Friday, January 10, 2020

"I never hit a pothole"

The title for this post is a direct quote made by many people who have suffered some tire failure. If you think about this claim for a moment and then think about the road conditions we all see in our day to day driving experience one has to wonder just where these people are driving.

In our life as drivers, I am sure that all of us have hit some objects other than simple 1" deep pot hole. Some objects could include bricks, lumber, railroad tracks, curbs, and puncturing or cutting objects such as nails or screws.

Here are some examples of tire damage I discovered in my work. The first three were each submitted with a written claim that the tire was "defective" so I can only assume the driver made little or no effort to inspect the tire or wheel for evidence of what might really have happened.
The last tire, with the wooden stake through the tread was submitted with a claim that the tire was defective because it was "making noise". IMO the noise would have been from the wood hitting the pavement at speed.

I have no expectation of changing the minds of those who want to make a claim of never hitting a curb or pothole or another object. I do want to relate the findings I recently discovered in a technical paper on tire forensics and impact damage.

In the paper, the reference studies involved a process of obtaining a couple dozen both new and used tires P type, LT type and sizes appropriate on Some Class-A RVs. The rim diameters ranged from 14" to 19.5". Tires came from 8 different tire companies. Each tire was inspected and no externally visible signs of damage were found.  Each tire was run on the appropriate DOT laboratory tests to confirm the tire was in good condition. Each tire was then mounted and hit with a heavy pendulum to simulate hitting some object or pothole on the road using a machine like this from STL company

 The tires were again visually inspected and any evidence recorded. Finally, every tire was run on a drum durability test under a load until failure occurred.

Failure Rate  100%
Miles to failure for new tires   1,826 mi  to  41,400 (avg. 11,586)
Miles to failure for used tires  5  mi      to    7,458   (avg. 2,092)

Can anyone here list every object they knowingly or unknowingly hit over the past 2,000 miles?

I know that I have posted a number of times that tires do not always fail at the instant of impact or damage. Clearly, these above studies confirm these observations.

Some reference material for those interested:
Price, V & Follen,G (2019). Road Hazard Impacts: Their Influence on Radial Passenger Tires and the Forensic Signs They Leave Behind
Bolden, G. C., Smith, J. M., & Flood, T. R. (2001). Impact Simulations in the Lab. Tire Technology International.
Bolden, G. C., Smith, J. M., & Flood, T. R. (2005). Impact simulations - what happens when a tire/wheel impacts a road hazard. Tire Technology International, 44.
Bolden, G. C., Smith, J. M., & Flood, T. R. (2006). Structural Impact Damage Under Varying Laboratory Conditions. Tire Technology International, 10.
Gent, A. N., & Walter, J. D. (2005). The Pneumatic Tire. Washington: National Highway Traffic Safety Administration, U.S. Department of Transportation.
Giapponi, T. R. (2008). Tire Forensic Investiagation Analyzing Tire Failure. Warrendale: SAE International.
McClain, C. P., & DiTallo, M. A. (2001). Tire Examination After Motor Vehicle Collisions. In K. Baker, Traffic Accident Collision Investigation (9 ed.). Evanston, Il: Northwestern University Center for Public Safety.
Tire Industry Association. (2005). Passenger & Light Truck Tire Conditions Manual.


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