Recalled Firestone tires mounted on Ford Explorers and other Ford Motor Co. trucks appear to fail more often on the rear driver's side than on other locations.
The automaker is trying to find a reason for the tendency, but says it does not undermine its contention that tread separations cited in complaints are a tire problem, not a vehicle problem.
Rear tire failures are more common than front tire failures, say experts, and are harder for a driver to control, especially in sport utility vehicles like the Explorer that are more prone to rolling over than passenger cars.
The database of Firestone complaints released by the National Highway Traffic Safety Administration shows that most Explorer rollovers have involved a rear tire failure, and a few more of them involved driver, or left, side tires than passenger side. Most complaints about Firestone tread separations have involved Explorers.