It's not often that you see more yellow T-shirts than black ones at a rock concert, but when seven-time Tour De France winner Lance Armstrong is throwing the party, the color of butter rocks.

"This is such a special day for me," the Austin-based sports hero announced Sunday at Auditorium Shores, wearing the red flip-flops of retirement. "10/2 is the most important day of the year for me."

Armstrong was diagnosed with cancer on Oct. 2, 1996.

The event was tagged Lance Thanks Austin, and the overriding theme was there on a proclamation Armstrong gave Mayor Will Wynn, calling Austin "the greatest city on the planet."

Reaffirming that he'll not race in the Tour again, Armstrong pointed to the side of the stage, where his three children and fiancée Sheryl Crow stood, and said, "There are four reasons why I'm not going back."

About 8,000 fans, many of whom rode their bikes and brought their kids and dogs, turned out for Sunday evening's event, which was capped with a set by Crow and band, mixing old faves with songs from her new album, "Wildflower," written in Spain while Armstrong was training last year.

"I'm likin' Austin, Texas," Crow said after her new hometown crowd vibrantly sang along on the chorus to "If It Makes You Happy."

The singer, in black and gold, added, "I can't wait to (move) here."

The three-hour show, featuring a rollicking opening set by Bob Schneider, was a breezy, laid-back antidote to the previous weekend's hot and dusty Austin City Limits Music Festival.

Admission was free, the lone concession gave out ice tea, and fans were urged to bring their own beer and food. Several wheeled in oversized coolers and carried picnic baskets.

Mike Garza of Austin said that he had felt left out by missing the ACL Fest but that he'd gotten a little of the flavor Sunday.

"I'm here mainly for Lance," Garza said, "but the free music is nice, too."

The sound, however, kept cutting out on a 15-minute video that summed up Armstrong's life after cancer. The star wasn't fazed.

"We're just going to flip the format and have fun today," he said, amid shouts of "We love you, Lance!"

His twin daughters, dressed in pink and scarlet, were a constant presence at stage right, with one of them wanting to join Crow onstage.

"Lance may be a big star," Crow said, gesturing to Grace, "but this one is the real star of the family."

At one point, brother Luke had to carry his kid sister, kicking all the way, from center stage.

Armstrong placed this celebration apart from previous post Tour de France sponsor-driven parades and concerts by saying, "This one is truly for you guys."

Armstrong footed the bill for the event, which was originally scheduled for Zilker Park but moved after the ACL Fest taxed the Zilker grounds.

"I did have to pay top dollar for the headliner," he quipped.

Then he turned serious, talking of how he's constantly been asked in the past few weeks how he, a legendarily intense competitor, will continue to challenge himself now that racing is over.

"How am I gonna fill that void?" he asked rhetorically. "Why don't we cure cancer? That's my fight. That's my race."

mcorcoran@statesman.com; 445-3652