Floyd Landis, who went from cycling's pinnacle to its depths to an unexpected role as the catalyst for a federal criminal investigation of his former team leader Lance Armstrong, told ESPN.com Monday night that he is retiring from the sport effective immediately.

Landis, 35, has been unable to land a salaried job in cycling since he went public last May with explosive allegations of organized doping involving Armstrong and other prominent cyclists and team officials, focusing on 2002-04 when Landis rode for the U.S. Postal Service team. He raced a handful of times as an unaffiliated rider during the 2010 season but said Monday he wants to move on with his life.

"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."

The 2006 Tour de France winner had his title stripped a year later after an arbitration panel upheld the results of a positive test for synthetic testosterone in a urine sample taken after a key stage of the race. Landis continued to maintain his innocence and unsuccessfully appealed the findings through one more round of arbitration. He spent his life savings and more than $1 million he raised from supporters on the legal wrangling and emerged broke and divorced but still outwardly defiant.

As the months went on, however, Landis privately began to consider telling the truth about his own doping past and the environment that he said fostered it. Last spring, he became convinced he was being blacklisted from being hired by an elite team or competing in top races and began sending e-mails detailing allegations against Armstrong and others to cycling officials and race organizers. Then he went a step further, meeting with U.S. anti-doping officials and federal investigators.

In May, the e-mails were leaked to several media outlets. Landis personally outlined his charges and his own culpability for the first time in a lengthy interview with ESPN.com, reversing years of dishonesty by admitting to extensive use of banned blood transfusions and drugs during his prime. Landis also revealed the ways in which he said riders beat more sophisticated testing.

Armstrong and everyone else named by Landis has continued to vehemently deny his allegations. However, federal authorities decided the claims warranted expanding an ongoing probe of performance-enhancing drugs in U.S. cycling. Investigators led by U.S. Food and Drug Administration special agent Jeff Novitzky began reviewing documents and interviewing former teammates and associates of Armstrong. Several have been subpoenaed to testify before a grand jury hearing evidence in Los Angeles, where the U.S. Attorney's Office is backing the inquiry.

Landis said he has considered calling it quits many times in recent months, "but I just couldn't follow through with it."

To underscore his intentions, Landis forwarded ESPN.com a copy of an e-mail he sent to U.S. Anti-Doping Agency chief Travis Tygart requesting that he be removed from the pool of athletes subject to doping controls.

"I don't want it to come across that I'm quitting because I'm bitter," Landis said.

But he added that he is disillusioned with what he termed systemic corruption and hypocrisy in cycling and said he is pessimistic that real progress can be made in changing its doping culture.

"I'm relatively sure this sport cannot be fixed, but that's not my job, that's not my fight," he said.

Bonnie D. Ford covers tennis and Olympic sports for ESPN.com.