Tony Stewart and Ryan Newman have wrecked during the final Daytona 500 practice, tearing up Stewart-Haas Racing's two cars before Sunday's season-opening race.Newman, the defending Daytona 500 winner, lost his right rear tire Saturday and his car spun out of control. Stewart, his car owner, was trailing tightly around Daytona International Speedway and couldn't avoid running into him.Newman's crew has pulled out a backup car.