WILMINGTON, DE, OCT 23 - Wayne Rainey, whose work ethic and bulldog perseverance changed the face of grand prix racing, is celebrating his 50th birthday today.From a dirt track beginning riding Shell Yamahas, he rose to become, first, a factory Kawasaki, then factory Honda road racer, winning the AMA Superbike Championship for both factories along the way.Then he set off for Europe, arriving at the start of the Golden Era of grand prix racing. Over a career that began in 1988 and ended in a gravel trap in Misano, Italy at the end of 1993, Rainey re-defined excellence.His 500cc GP career was spent riding for mentor Kenny Roberts, who once said of Rainey that he was like a bulldog. "Once he gets ahold of something he doesn't let go," Roberts said.Racing a series of increasingly volatile motorcycles, Rainey was part of one of the most decorated group of motorcycle racers ever. Every one of them, from Kevin Schwantz to Mick Doohan to Eddie Lawson to Wayne Gardner, would win the 500cc World Championship and most more than once. Doohan won five titles, Lawson four. Rainey is the last American to win serial World Championships, taking the title every year from 1990 through 1992.A pivotal moment in his career came in Anderstorp, Sweden late in the 1989 season. It was there that a small riding error led to a high-side that essentially sent Eddie Lawson (Rothmans Honda) to the last of his four 500cc World Championships. Rainey didn't forget that lesson and returned in 1990 ready to fight.The 1990 season was arguably his best. Rainey put together a scoring line that looked a lot like what Jorge Lorenzo did for most of this season. He was first or second in every race but two; a third in France and a mechanical DNF in Hungary, where he'd already clinched the title.Rainey later told his biographer, Michael Scott, whose "Wayne Rainey: His Own Story," is one of the definitive biographies of a motorcycle racer, "I just wanted to devastate Eddie (Lawson). I don't think he was ready for a teammate like me. Maybe he thought he could control me, but at that stage I was past being controlled." Looking at Rainey's points run later that night, Kevin Schwantz said, "Just once I'd like to have a season like that."Schwantz vs. Rainey is the last great rivalry of the premier class. With Rainey gone, Schwantz lacked the motivation and racing was no longer fun. Mick Doohan took up the torch and devastated a series of lesser opponents until his career ended in a gravel trap in Jerez. Alex Criville and Kenny Roberts Jr. took solo titles before the Valentino Rossi era began. Rossi has had a number of worth adversaries, but none who were his equal and none would provide the same intensity or longevity of the Rainey-Schwantz wars.Rainey accumulated 24 wins and 65 podiums before crashing out of the lead in Misano, breaking his sixth thoracic vertebrae. To that point in the season he'd won four races and was in front in the championship. By missing the final three races he finished second to Schwantz, appropriately at a gap of 34 points.After a brief retirement, Rainey took up team management, but quickly discovered that his riders didn't share his commitment to winning. He retired to Monterey, California, where he lives with his wife, Shae, and son, Rex, in a house with a view of the Monterey Bay.Rainey wasn't the first American to win a premier class title, nor will he be the last, but the standard he set is one that every rider with even a hint of pride strives to live up to. For that the racing world is eternally grateful.Happy birthday, Wayne.