Floyd Landis at the New Pathways for Pro Cycling conference in Australia (Image credit: kathryn Watt)

Floyd Landis has turned his back on cycling. He is retiring immediately and moving on to other things, he told espn.com.

His doping disclosures last year have kicked off a major US investigation, but he is pessimistic about the outcome. "I'm relatively sure this sport cannot be fixed, but that's not my job, that's not my fight," Landis said.

Landis has been unable to find a new team, and is quitting for that reason. “I don't want it to come across that I'm quitting because I'm bitter,” he said.

"I've spent five years trying to get back to a place that I can never really go back to, and it's causing more stress than is worth it," Landis said. "There must be more to life than this.

"I've been riding my bike a lot, trying to figure out life, which is the same reason I did it to start with, so I've come full circle. I'll always ride my bike. But I'll never start on a line on a road and try to get to another line on a road faster than another guy. That's over."

Landis won the Tour de France in 2006, but lost the title after testing positive for testosterone during the race. He maintained his innocence and put up a major public defence, before finally losing the fight.

In the spring of 2010, however, he changed his mind and started talking with investigators and cycling officials about doping in cycling.

He eventually went public with the information, confessing to year-long doping practices, and exposing the doping practices of various teams with which he had been associated. All those named by him have publicly denied the charges.