DRIVING SOUTH ON I-5, AT APPROX 70MPH, REAR TIRES WENT FLAT. FIRST, REAR PASSENGER TIRE BLEW TO SHREDS AND SIDEWALL SEPARATED. CAR STARTED TO FISHTAIL AND REAR, DRIVER SIDE, TIRE WENT FLAT, PROBABLY ROLLED OFF OF THE RIM. DEALERSHIP LOOKED AT TIRES AND CONFIRMED THAT TIRE IS DEFECTIVE, DAMAGE NOT CAUSED BY ROAD HAZARD. HAVE NOT YET SUBMITTED PROBLEM TO FIRESTONE. IN PROCESS OF FILING CLAIM. CURRENTLY HAVE POSSESSION OF ALL FOUR TIRES. REPLACED ALL ORIGINAL TIRES 'CAUSE WIFE IS AFRAID TO DRIVE VAN.*AK