Dave Zabriskie powered to a dominating individual time trial victory and three-time Tour of California winner Levi Leipheimer was second to cut teammate Chris Horner's overall lead to 39 seconds Friday after the sixth stage of the 2011 Amgen Tour of California.

Zabriskie, the Garmin-Cervelo rider who has finished second overall three times in the event, completed the 15-mile course in 30 minutes, 36 seconds. Leipheimer, riding for Team RadioShack, finished in 30:50, and Team HTC-Highroad's Teejay Van Garderen was third in 31:16.

Horner, who took the lead with a solo mountaintop win in the fourth stage, finished sixth today -- 50 seconds behind the winner. Horner began the day with a 01:15 lead over Leipheimer.

The seventh stage Saturday is a 75.8-mile mountain leg from Claremont to Mount Baldy.