The National Highway Traffic Safety Administration denied the petition of Bridgestone/Firestone for a defect investigation of the Ford Explorer Feb. 12.
The data does not support BFS's contention that Explorers in general or two-wheel-drive Explorers from 1995 and later in particular, are more likely to roll over when a tire tread separates than other sport-utility vehicles, according to NHTSA.
This represents a major blow to Bridgestone/Firestone, which had hoped for the safety agency to back its position that the design of the Ford Explorer is at least as much to blame for the rollover accidents that killed 271 people as the failure of Firestone tires mounted on the vehicles.
The same day, however, the U.S. Seventh Circuit Court of Appeals agreed to hear the firms' appeal of an Indianapolis district court judge's certification of a product liability class-action suit against Ford and BFS.
Both companies said they were ``pleased'' with the decision. ``We believe the law is clear and look forward to an opportunity to present our case,'' a Bridgestone/Firestone spokeswoman said.
The Nashville, Tenn.-based tire maker petitioned NHTSA last May 31 for an investigation into the Explorer. This action came nine days after Ford announced the unilateral replacement of 13 million Firestone tires-a move Bridgestone/Firestone said was unnecessary-and 10 days after BFS publicly severed ties with the auto maker.
BFS based its petition on a study it commissioned from Dennis Guenther, an Ohio State University engineering professor. Mr. Guenther found in his research that the Explorer was prone to oversteer, which in turn made it more likely to roll over after a tread separation.
In October, NHTSA complained that Firestone hadn't turned over further promised data, while BFS said Mr. Guenther's research was ``ongoing'' and would be given to the agency as it became available.
After receiving the BFS data as well as information from Ford and the agency's own Office of Research and Development, NHTSA found Mr. Guenther's tests ``objective and performed under acceptably controlled conditions.''
Mr. Guenther's finding that model year 1995 and later two-wheel-drive Explorers had less understeer than other Explorers was ``literally accurate,'' according to NHTSA's technical memo on the matter.
``However, data reflecting tests of a more representative sample of SUVs by (NHTSA) and Ford show that the level of understeer of these Explorer models is greater than or similar to those of many other contemporaneous SUVs,'' the agency said.
NHTSA also concluded that ``the available data do not support Firestone's assertion that the Explorer loses much of its understeer when fully loaded.''
Explorers aren't unique among SUVs in developing oversteer after a rear tread separation, the agency said. Of 25 SUVs tested by Ford, 20 showed oversteer characteristics in that circumstance.
``A vehicle cannot be found to contain a safety-related defect...solely because it has not been designed to preclude linear range oversteer following an unexpected, catastrophic event such as a tread separation,'' the agency said.