DETROIT Ford Motor Co. is recommending that Explorer owners add more air to their Firestone tires, a day after the tire manufacturer criticized the automaker in congressional testimony as setting the air pressure too low.
Ford released a letter Friday saying it was raising its recommendation to 30 pounds per square inch from 26 psi .
A Bridgestone/Firestone Inc. executive told Congress on Thursday that the 26 psi level Ford recommends for Explorers is lower than what Bridgestone/Firestone suggests and makes the popular sport utility vehicle less safe.
"We now know that at 26 psi there is a low safety margin for the Explorer as compared to some other SUVs," Bridgestone/Firestone executive vice president John Lampe said.
Bridgestone/Firestone last month recalled 6.5 million ATX, ATX II and Wilderness AT tires, most of which were original equipment on Explorers. Federal investigators are investigating the possible role of the tires in wrecks that resulted in more than 100 deaths and 400 injuries.
A lower air pressure gives tires more grip and a softer ride, but causes them to wear faster and creates more internal heat because of greater friction with the road. Ford has said it set the recommended pressure for Explorer tires at 26 psi in 1989 to improve stability and ride, and that Bridge-stone/Firestone had agreed with the recommendation at the time.
But experts for trial attorneys suing the two companies have speculated that heat from the lower pressure weakened the bond between the tires and their treads. Thousands of people, most of them Explorer owners in warm-weather states, have reported tread separations, blowouts and other problems with the tires.
Ford has consistently blamed the problems on Firestone and said the design of the Explorer was not at fault.