Decatur Only Source Of Problem Tires--Firestone

NASHVILLE, Tenn.--Bridgestone/Firestone will not expand its recall of suspect Firestone tires. Instead, it is reporting that its own investigation is centering on the design of its previously recalled tires and the manufacturing process at its Decatur, Ill. facility.

The company has been resisting efforts from the National Highway Traffic Safety Administration and various consumer groups to include other suspect tires--including those made at other Firestone plants--in the recall effort.

In addition to Firestone’s own analysis, an examination by Dr. Sanjay Govindjee, the independent materials expert retained by the company, is ongoing. He did not offer an opinion on Firestone’s latest report.

“No one is more interested in finding the answer than we are,” said John T. Lampe, chairman, chief executive officer and president. “Our technical team reports that we are concentrating our efforts on a number of factors, including tire design, the tire’s components and external factors, all of which warrant further examination,” he said.

Lampe added that as the company continues to search for the cause or causes, it will provide periodic updates on the status of the company’s internal analysis.

A clear difference appears to exist between ATX and same-size Wilderness AT tires, Lampe said.

As part of the company’s analysis it is examining every aspect of the tire’s design, including tread design and the placement of the tire’s components within the makeup of the tire itself.

This is a significant area of examination because, according to the company, its data shows a clear difference in the rate of tread separation claims between the P235/75R15 Wilderness AT tire and the same size Radial ATX. These Wilderness AT claims are less than one-tenth of that experienced by the P235/75R15 ATX tire made in Decatur. The disparity in the rate of tread separations between the two tires has led the company to closely analyze how the two tires differ in design.

In addition to examining the differences in the individual design of each tire, the company said it is taking a hard look at the various components and materials that comprise each tire, including the interbelt material which is an important factor in the strength between the steel belts. The interbelt area includes the steel cords that are made into two belts coated with rubber and a strip of rubber between the edges of the two belts. The company is looking closely at the interbelt area because that is where tread separations tend to occur.

Beyond its focus on tire design, Firestone is also examining the manufacturing process employed at its Decatur plant. Specifically, the company is analyzing how its Decatur-made Wilderness AT tires perform in relation to those Wilderness AT tires made at its other plants. A review of the company’s claims data shows that its Wilderness AT tires made in its plants in Wilson, N.C. and Joliette, Quebec, have a much lower number of performance-related problems, a claim disputed by some consumer safety advocates who maintain that the entire line of tires is suspect.

While the claims rate for its Decatur-made P235/75R15 Wilderness AT peaked in 1996, the first year the tire was produced at that plant, that rate was still significantly lower than the ATX claims rate. The rate of claims for the Wilderness AT tire dropped in 1997 and continued to decline in subsequent years, according to Firestone.

Running on an under-inflated tire significantly increases the heat and stress that the tire experiences, especially when carrying heavy loads, traveling at high speeds or driving in high-temperature climates. Proper tire inflation is important because all tires can lose about 1 pound per square inch of pressure per month.

The company said it is looking at factors that generate excessive heat and weaken the tire’s construction in the belt-edge area, making the tire more susceptible to failure.

According to Firestone’s data, “the vast majority of claims on the recalled tires involve a rear tire, and the clear majority of those claims involve the left rear tire.” In order to fully understand this phenomenon, Firestone said it must fully understand how the loading or stress from a vehicle affects the overall strength and performance of the tire.

“Based on the company’s review to date, our technical teams believe the performance issue with the tire ultimately will be the cumulative effect of tire design, tire components and the interaction of the tire with the vehicle,” said Lampe.