ORIGINAL EQUIPMENT ON A 1998, FORD, LT225/75R16 SIZE, DOT: VD111XD437. TIRE DISINTEGRATED WHILE DRIVING AND COMING THROUGH BOTTOM OF VAN, INJURING A PASSENGER. SPARE TIRE WAS PUT ON VEHICLE, AND TREAD SEPARATED AT HIGHWAY SPEEDS, CAUSING DAMAGE TO VEHICLE. FIRESTONE HAS BEEN NOTIFIED. *AK