Armstrong spoke briefly at the sunrise start of the ride, telling the crowd he's faced a "very difficult" few weeks. But he did not otherwise mention USADA's report detailing evidence of performance-enhancing drug use by Armstrong and his teams or the sanctions.
International Cycling Union (UCI) President Pat McQuaid has scheduled a Monday news conference in Geneva where he's expected to announce if the sport's governing body will accept or appeal the sanctions to the Court of Arbitration for Sport.
"I've been better, but I've also been worse," Armstrong, a cancer survivor, told the crowd, repeating a line from his remarks at Livestrong's 15th anniversary celebration Friday night.
Armstrong wore a black t-shirt instead of the charity's signature yellow derived from the yellow jerseys given to the winner of the Tour de France.
"Live strong, be safe," Armstrong said before the first riders left the gate.
Armstrong stepped down as chairman of Livestrong on Wednesday. That same day, most of his personal sponsors, including Nike and brewing giant Anheuser-Busch, dropped their contracts with him or said they would not renew when current deals expire.
USADA has said Armstrong should be banned and stripped of his Tour de France his titles for what the agency called "the most sophisticated, professionalized and successful doping program that sport has ever seen" within his U.S. Postal Service and Discovery Channel teams.
The USADA report said Armstrong and his teams used steroids, the blood booster EPO and blood transfusions. The report included statements from 11 former teammates who testified against Armstrong.
Armstrong denies doping, pointing to hundreds of passed drug tests. But he chose not to fight USADA in one of the agency's arbitration hearings, saying the process was biased against him. Former Armstrong team director Johan Bruyneel is also facing doping charges, but he is challenging the USADA case in arbitration.
Tour de France director Christian Prudhomme is waiting on the UCI's decision before removing Armstrong's name from the record books as the race prepares to celebrate its centenary edition next year.
Armstrong won consecutive Tours from 1999-2005. Prudhomme said the Tour will have no official winners for the seven races Armstrong won if he is stripped of his victories by the UCI.
USADA has said the Tour titles should not be given to other riders who finished on the podium. The agency said 20 of the 21 riders on the podium in the Tour from 1999 through 2005 have been "directly tied to likely doping through admissions, sanctions, public investigations" or other means. It added that of the 45 riders on the podium between 1996 and 2010, 36 were by cyclists "similarly tainted by doping."
Several riders at Sunday's event, which organizers said raised $1.7 million, said they support Armstrong completely or separate his cycling career from his charitable work. Livestrong has raised about $500 million to fight cancer and support victims since it was founded in 1997.
"If he did it, he should face the consequences," said Sonya Garrison, who was riding in memory of her grandfather and to support a friend with cancer. "But this is for the cause. More people are here for the cause than just for him."
Rider Steve Weinberg said he's "still a Lance fan" regardless of the doping charges.
"I think everyone was doing it back then," Weinberg said, noting Armstrong's passed drug tests. "That whole thing needs to go away."