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Firestone Announces the Completion of the Independent Expert’s Analysis
• Dr. Sanjay Govindjee Confirms No Single Factor
• Findings Shared with Public

Nashville, Tenn. – February 2, 2001 – Firestone today announced the completion of Dr. Sanjay Govindjee’s analysis and technical report detailing why the recalled ATX and Decatur-produced Wilderness AT tires, primarily on Ford Explorers, experienced a higher rate of tread separation claims. Dr. Govindjee’s findings and analysis independently confirms that no single factor caused an increase in tire failure.

"In all cases, failure rates for the recalled tires are fractions of a percent and thus determining a single cause for the tire failures is an unrealistic expectation," said Dr. Govindjee, an associate professor of civil engineering at the University of California at Berkeley. "From a mechanical and materials engineering perspective, the phenomena of belt separation in these tires resulted from a crack that grew in the rubber between the two belts. This cracking is influenced by a number of factors, including climate, design of the tire, manufacturing differences at Firestone’s Decatur plant and usage factors."

Dr. Govindjee examined recalled tires to determine what could cause a fatigue crack or belt separation to grow between the two steel belt layers of the tires. His analysis, which included standard testing and new lab and field testing, found that climate played a critical role in reducing the material properties or capacity of the tires. For example, tires from warmer climates showed a substantial degradation in their material properties; further, tires that were run at high speeds, in highly loaded vehicles or at low inflation display pronounced heat build-up. While the effect of temperature on the capacity of the interbelt materials was confirmed, he also found the demands on the tires from extra loading were important in pushing a fatigue crack to grow. Further, his analysis showed that the interbelt material properties of the Decatur-produced tires were substantially different from those at other plants and had a higher propensity to fracture. His analysis also found design differences in the Radial ATX could lead to a higher propensity to fatigue than the Wilderness AT.

Dr. Govindjee focused on a mechanical and materials engineering analysis and, as a result, has some differences in scope and focus from Firestone’s internal investigation, released December 19, 2000, but his overall conclusions provide additional information consistent with the company’s findings.

"Firestone’s technical staff is now thoroughly reviewing Dr. Govindjee’s report as part of our quality assurance and continuous improvement program," said John Lampe, Bridgestone/Firestone Chairman, CEO and President. "We thank Dr. Govindjee for his hard work. I am confident that with our own internal review, combined with Dr. Govindjee’s analysis, we have determined why some of our tires experienced a higher rate of tread separation claims and that our recall in August was more than adequate to protect the public."

Dr. Govindjee used information provided from Firestone and its research center and laboratory, independent laboratories and a survey of material properties from returned tires, analysis of tire loading on the Ford Explorer, analysis of heating factors – which included an analysis of tire inflation pressure, loading and speed – and extensive finite element modeling to determine how these factors affect tire life.
In addition, Dr. Govindjee used field data on Ford Explorers regarding actual dynamic loading or forces placed on the tires by the vehicle. This data was collected at Firestone’s test track in Acuna, Mexico on a 1998 Ford XLT Explorer four-wheel drive. Measurements were performed at four different inflation pressures, four different cargo loads and at different speeds.
Dr. Govindjee was hired by Firestone in September to provide an independent analysis of its recalled tires. While Firestone provided information and data requested by Dr. Govindjee, his work was conducted independently from the company’s own internal review and analysis.

Firestone has provided Dr. Govindjee’s report and findings to the National Highway Traffic Safety Administration and other governmental groups.

"I am grateful to Dr. Govindjee for his untiring efforts in this analysis," said Lampe. "Finding the root cause of why some of our P235/75R15 ATX and Decatur-produced Wilderness AT tires failed was a priority for this company and we know it was extremely important to our customers. Dr. Govindjee’s report provides another step forward in helping put systems in place to prevent the difficulties we encountered last year from happening again. Overall, his independent report supports our earlier findings, which assures me that we have taken the right course and are putting into place the necessary and appropriate corrective actions in building world-class tires, for which this company is known."

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