July 8 (Bloomberg) -- Lance Armstrong’s Tour de France comeback looks good after he pushed into second place. Now he’s working with Damien Hirst, the U.K. artist known for pieces including a diamond-encrusted skull, to get his bike in shape.

Armstrong, just off the pace after five of 21 stages, wrote on his Twitter social-networking feed he was “speechless” after seeing Hirst’s design on the bike’s frame. He didn’t give details. The artwork features butterflies, according to Hirst’s business manager Frank Dunphy.

“Damien has made a gift of the design” to promote Armstrong’s cancer charity, Dunphy said in a phone interview. “We’ve known Lance Armstrong for some time.”

The bike will be used for the final stage of the race, which ends July 26 in Paris, Dunphy said.

Armstrong, 37, is seeking a record-extending eighth Tour title after coming out of retirement. So far, he has been using a black-and-white Madone bike from Trek Bicycle Corp. with yellow detail on the wheels and the name of his charity, Livestrong.

Armstrong survived testicular cancer before winning seven straight Tour titles through 2005.

Damien Hirst, who raised 111.5 million pounds ($178 million) selling his works at Sotheby’s London in September, joined an investment group in 2007 that bought his platinum, diamond-crusted skull for $100 million. He’s also preserved cows in formaldehyde and sold spot paintings. Last year, he said he would stop making the spin and butterfly paintings that are among his top-selling works.

To contact the reporter on this story: Alex Duff in Madrid at aduff4@bloomberg.net.

Last Updated: July 8, 2009 12:06 EDT