BIRMINGHAM, Ala. — Mike Helton has seen Talladega Superspeedway's capacity expand in boom times and shrink along with the crowds at one of NASCAR's signature tracks, moving in tandem with the sport's ebbs and flows. The speedway cut its seating capacity nearly in half in recent years, going from 140,000-plus to 78,000 as the sport dealt with a recession and the challenge of getting fans back in the stands when they can watch at home on flat-screen TVs. "We want to be relevant, and Talladega wants to be relevant," said Helton, NASCAR'spresident, who ran Talladega Superspeedway from 1989 through 1993.