Brazil's Helio Castroneves won pole position for the Indianapolis 500 in Saturday's time trials, outfighting Australian teammate Ryan Briscoe to give Roger Penske a record 15th Indy pole.

Two-time Indy 500 winner Castroneves, found not guilty last month on US federal tax evasion charges, drove his Honda-powered Dallara to a four-lap qualifying average of 361.883km/h around the 4km oval.

"What a great day. After all that has been happening in my life, to be on pole position here, it's incredible," an emotional Castroneves said.

Castroneves, the 2001 and 2002 Indy winner who won a US television 'Dancing with the Stars' title, telephoned his sister and manager Katiucia, also acquitted on tax charges, as qualifying ended and his pole spot was secured.

"After all that we've been through, she helped me through this. This is what I know. This is my life. This is racing. And I have to thank the fans for their support. Without them I don't have the strength to do this."

Only the top 11 spots in the 33-car field for the 24 May race were at stake Saturday with time trials Sunday for the next 11 spots, next Saturday for the last 11 places and 17 May for slower cars to bump their way onto the grid.

Chaotic speed search

Indy's unique qualifying system created a chaotic speed search on Saturday with every car given three attempts, tempting drivers to pull qualified cars from the lineup to make a late bid at improving grid position or challenge for pole.

Briscoe posted the early time to beat but Castroneves bumped him off the pole.

"You don't want to bump your teammate off, but it's the Indianapolis 500. We do everything we can," Castroneves said.

Briscoe, whose car is also owned by Indy legend Penske, tried to return the favour.

He made the biggest gamble by pulling the second-fastest qualified car from the lineup in the final minutes of qualifying to take a run at the pole.

A poor first lap doomed the bid but Briscoe recovered to hold onto his spot in the middle of row one, although with a slower speed average at 360.703km/h.

"You can't say we didn't try," Briscoe said. "Great drive by Helio. I came into a big gust of wind at the start on the backstretch and that killed all four laps. But it's great for Team Penske, 1-2 on the front row."

Patrick far off

Scotsman Dario Franchitti, the 2007 Indy winner who missed last year in a failed stock car bid, was on the outside of row one.

"It would be nice to get on the pole but I've won from third before," said Franchitti. "Honestly, that was about all the speed the car had in it."

Defending race and Indy-car champion Scott Dixon of New Zealand was fifth and will start in the middle of row two, flanked inside by American Graham Rahal and on the outside by Brazilian veteran Tony Kanaan.

Row three features Brazil's Mario Moraes, American Marco Andretti and Aussie Will Power with Danica Patrick on the inside of row four and England's Alex Lloyd beside her after taking the final spot in the last minutes of qualifying.

"I've never been this far off at Indy," Patrick said. "It really just was slow."

Lloyd bumped Japan's Hideki Mutoh on the penultimate attempt of the day and withstood a bid from countryman Justin Wilson, who had an earlier run thrown out for wrongly positioned ballast and was too slow in his deadline attempt.

"We lost the balance in practice. We were struggling," Lloyd said. "We went back to the garage and went out there and just nailed it. The car felt great. I'm thrilled to be on day one."

Dutchman Robert Dornbos crashed in a morning practice session while separate incidents in the afternoon claimed England's Dan Wheldon and Frenchman Nelson Phillippe. All three escaped unharmed and planned to try to qualify later.