Rubber Mix Source of Tire Woes

Tuesday, December 19th 2000, 12:00 am

By: News On 6

WASHINGTON (AP) â€” Bridgestone/Firestone Inc. has told government officials investigating 148 U.S. traffic deaths linked to its tires that the problem stems from a faulty design and unique manufacturing process at its Decatur, Ill., plant, The Associated Press has learned.

The Nashville, Tenn.-based company said it would release its findings about why some tires came apart on Tuesday and would not comment beforehand.

Two sources speaking on condition of anonymity said Bridgestone/Firestone officials told congressional investigators and the National Highway Traffic Safety Administration that the Decatur plant uses a different process to mix rubber that has resulted in the tread peeling off the tire, causing the accidents.

One of the sources works on Capitol Hill; the other is an official familiar with the report. Both spoke late Monday.

The tire maker also told investigators there was a problem with the wedge area of the tire, located near the shoulder where the tread meets the tire wall. And it continued to blame Ford Motor Co. for recommending a lower inflation pressure.

The company's recall, which began in August, is one of the largest in U.S. history. The tire problems have been subject to high-profile congressional hearings and investigation and prompted Congress to pass an overhaul of U.S. tire safety regulations.

As reports of traffic deaths mounted over the summer, the company was unable to explain why so many tires came apart on the road.

The report backs up the company's contention that the problem is concentrated in Decatur.

The current recall is concentrated on â€” though not limited to â€” tires made in Decatur.

In its report, Firestone blames the failures on a complex combination of factors, including temperature and type of climate they're used in, loading of the vehicles, speed, place of manufacture, shoulder design and tread design.

And Firestone still insists that the lower inflation pressure recommended by Ford Motor Co. played a role in the tire failures.

Bridgestone/Firestone also says that the Explorer's weight increased beginning in 1992, requiring a higher inflation pressure that left a small margin of safety for the tires, the congressional source said.

Ford recommended that Firestone tires on the Explorer sport utility vehicle be inflated to 26 pounds per square inch, while Firestone recommended 30 psi.

A Ford spokesman, Ken Zino, said the auto maker is continuing its investigation and has yet to come up with a root cause for the failures. He said the Explorer's weight has not changed significantly.

``In our discussions with both NTHSA and Firestone we discussed tire design and manufacturing problems, and we still don't see the Explorer as the issue,'' Zino said.

NHTSA links 148 deaths and more than 525 injuries in the United States to separations, blowouts and other tread problems in Firestone's ATX, ATX II and Wilderness AT tires, 6.5 million of which were recalled during the summer, many made at the Decatur plant. Many of the tires were standard equipment on the Ford Explorer.

Ford and Firestone officials briefed NHTSA on the status of the investigation last week. Firestone officials met Monday with congressional investigators, while Ford officials plan to meet with them Thursday.

The Decatur plant uses a process known as pelletizing, where rubber pellets are blended with a lubricant to create the rubber that coats the steel belts of the tire.

This process is unique to Decatur. Other plants use a slab system that does not involve pellets.

The lubricant apparently causes a breakdown in the tire that can cause separation of the tread, the sources said.

But the vice president of the United Steelworkers local 713 at the Decatur plant said it isn't fair to drop the whole problem on the doorstep of one factory.

``I feel like they're questioning our workmanship,'' Harland Smith said. ``We have tires out there with 80,000 miles on them. ... We have workers at our plant that drive on them same tires and never took them in for the recall.''

Smith believes the tire failures more likely came from overall design problems and more significantly from the lower inflation pressure recommended by Ford.

``Underinflating the tires puts more heat and stress on them,'' Smith said. ``Most of the failures happened in hot states down south.''