Doping allegations may be bringing down yet another larger-than-life sports great.

Disgraced cyclist Floyd Landis is accusing Lance Armstrong of using performance-enhancing drugs, a charge that could unseat him as the straight-laced face of competitive cycling.

Some of Landis’ claims:

• He used human growth hormone, testosterone and other substances years before being stripped of his 2006 Tour de France title.

• He was in charge of checking on blood at Armstrong’s apartment for transfusions to potentially mask drug use.

* Armstrong, 38, and coach Johan Bruyneel, 45, bribed an official to toss test results that showed the cycling great was blood doping.

• He accused 16 others in the cycling world of doping

Armstrong vehemently denied the charges Thursday.

“We have nothing to hide. We have nothing to run from,” said the seven-time Tour de France champ, who suffered minor injuries while racing in California yesterday. “Floyd lost his credibility a long time ago.”

Landis, 34, said he made  his confession to “clear his conscience” and because he doesn’t “want to be part of the problem anymore.”

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As the shadow of doping scandals grow, the integrity of sports is eroding, experts said.

“Elite sports has become an ethics-free zone, and one reason elite athletes lie so well is because they don’t feel guilty,” said John Hoberman, author of “Testosterone Dreams: Rejuvenation, Aphrodisia, Doping.” “They say, ‘This is what you expect of us, what you want us to deliver,’ which are essentially inhuman achievements.”

The use of performance-enhancing drugs in general seems to be a new norm, whatever the ethical implications, local cyclists said.

“A lot of people feel that most anyone who won anything at the turn of the millennium doped,” said Schuyler Shepherd, 20, of Bushwick, who works at a Union Square bike shop. “So a lot of people don’t have issues with that Lance doped but more his response. He’sbeen so confrontational.”

As cycling officials investigate Landis’ claims, sports fans will continue to weigh what constitutes cheating.

“There’s scuffing a baseball, and there’s getting involved in a systematic program to willingly alter your body chemistry,” said Dan Schmalz and Andy Shen, of cycling website nyvelocity.com, in a joint statement. “One seems more innocent and far less dangerous than the other.”

The AP contributed to this story.

emily.ngo@am-ny.com