With the cycling season kicking into high gear, the strongest doping allegations yet against Lance Armstrong surfaced yesterday in a barrage of detailed messages from Floyd Landis, the disgraced rider and former teammate who finally confessed to years of cheating himself.

In a series of e-mails sent to sponsors and sports officials, Landis alleged Armstrong not only joined him in doping but taught others how to beat the system and paid the former president of the International Cycling Union to keep a failed test quiet.

"We have nothing to hide," Armstrong said at an impromptu news conference before the fifth stage of the Tour of California.

"Credibility," the seven-time Tour de France winner said in Visalia. "Floyd lost his credibility a long time ago."

In two e-mails obtained by The Associated Press, Landis also admitted for the first time what had long been suspected — that he was guilty of doping for several years before being stripped of his 2006 Tour de France title.

"I want to clear my conscience," Landis told ESPN.com. "I don't want to be part of the problem any more."

Neither Landis nor his family returned repeated messages from the AP.

Landis alleged that Armstrong and longtime coach Johan Bruyneel paid former UCI president Hein Verbruggen to cover up a test in 2002 after Armstrong purportedly tested positive for the blood-boosting drug EPO. The UCI denied changing or concealing a positive test result.

ARMSTRONG CRASHES

Lance Armstrong crashed during the Tour of California yesterday, sending him to the hospital for precautionary X-rays on the day he was accused of doping by Floyd Landis.

The cyclists were on a two-lane road outside Visalia a few miles into the race when a rider in the main group skidded on some gravel and fell, causing others, including Armstrong, to crash. Armstrong resumed riding but had to quit the race because of his injuries.

"I tried to give it a go but my eye was swollen so I couldn't see properly and the pain in the elbow prevented me from holding the bars for the remainder of the stage," Armstrong said. "It was a relief to learn there were no breaks."

Michael Rogers of Australia took the overall lead with his second-place finish in the 121.5-mile fifth stage that ran from Visalia to Bakersfield. Peter Sagan of Slovakia won the stage in 4 hours, 52 minutes and 58 seconds.

AUTO RACING

KANAAN FASTEST

Tony Kanaan ran a fast lap of 226.775 mph yesterday before rain ended Indianapolis 500 practice about 45 minutes early.

Paul Tracy had the second-fastest lap at 226.322 mph, Hideki Mutoh was third at 226.230 and Marco Andretti was fourth at 226.108. Scott Dixon had the fastest lap the previous two days, but was just the 13th-fastest yesterday.