DETROIT (AP) _ Ford Motor Co. officials said Thursday that new information indicates Firestone tires are more prone to tread separations than those made by Goodyear.
Firestone officials challenged the report, which was released in advance of Tuesday's congressional hearing to examine the safety of Firestone tires and the Ford Explorer.
Ford based its findings on an analysis of government and internal research along with claims data provided by Bridgestone/Firestone Inc.
The automaker said that between 1995 and 1997, its Explorer sport utility vehicles were fitted with equal numbers of Firestone and Goodyear tires as original equipment.
Ford said there were 1,183 tread separations associated with the 2.9 million Firestone tires, and just two with an equal number of Goodyear tires.
Ford said the research indicates the disparity in performance was due to differences in tire construction despite using the same specifications as set out by the automaker.
Richard Parry-Jones, Ford group vice president for global product development and quality, said Firestone tires ran hotter than Goodyear tires because thinner layers of protective rubber were used between steel belts.
``To run at a cooler temperature is a tire's first line of defense against tire failure,'' he said.
Parry-Jones said the strength of the bond between steel belts, known as ``peel strength,'' was lower in Firestone tires compared to Goodyear tires and other brands tested.
Bridgestone/Firestone spokeswoman Jill Bratina said Ford was using incorrect data to justify its current replacement program.
``What they don't tell you is that data is related to the tires that were involved in the August 9th recall. We took responsibility for those tires and took them off the road,'' Bratina said.
The more important issue was what happens after tread separation, she said, adding that accident crash data shows Ford Explorers _ the world's best-selling SUV _ are more likely to roll over at that time than other SUVs.
``When the tread separates on a tire, the driver should be able to pull over, not roll over,'' Bratina said.
Ford last month began replacing 13.5 million Firestone tires that were not included in last year's government-directed recall of 6.5 million tires used mainly as original equipment on Explorers.
The federal government has linked at least 174 deaths and more than 700 injuries to the tires, some of which experienced tread separation.
In some of the accidents, Ford SUVs rolled over, giving rise to speculation about the vehicle's safety.
Firestone has asked the federal government to investigate the safety of the Explorer.
The automaker has maintained the problem is with the tires, not its vehicles.