Ford Motor Co. on Thursday defended its decision in May to replace 13 million Firestone tires free of charge.
Ford said new safety data show that the tires, manufactured by Bridgestone/Firestone Inc., had a higher propensity to shred in comparison with other brands.
Ford released the data Thursday, one week in advance of a U.S. congressional hearing on tire safety.
Ford and Bridgestone/Firestone, a subsidiary of Japan's Bridgestone Corp., have been locked in a high-stakes battle over the safety of Firestone tires after Bridgestone/Firestone was forced last summer to recall more than 6 million Firestone tires that had been mounted mainly on Ford Explorer sport utility vehicles.
The battle escalated in May when Ford announced it would replace 13 million Firestone tires mounted on all Ford vehicles as a precautionary measure.
Bridgestone/Firestone responded by announcing it was ending all business ties with Ford.
Ford said new data reveal that the treads on Wilderness tires manufactured at two U.S. Bridgestone/Firestone plants that were not subject to last year's recall were more likely to shred after more than four years of use than other comparable brands.
The Wall Street Journal said Thursday that Ford had registered 168 cases of Firestone tires shredding on Ford cars other than the Explorer.
Ford also said the Explorer -- which Bridgestone/Firestone claims has a tendency to roll easily -- had a much lower accident rate than other sport utility vehicles.