Parnelli Jones and Al Unser

The first-round matchups in the "Champions of the 500" bracket challenge open for voting now feature some of the most legendary names in Indianapolis 500 Mile Race history -- including two drivers with the same name. Vote now until noon ET April 27 to determine who will join Helio Castroneves, A.J. Foyt, Bobby Unser and Bill Vukovich in the quarterfinal round.

Sixteen of the greatest Indianapolis 500 winners – revered names ranging from Mears to Montoya, Shaw to Wheldon – were selected to square off in a digital voting platform running through May 23, leading to the historic 100th Running of the Indianapolis 500 presented by PennGrade Motor Oil on May 29. The current pairings up for vote are: four-time Indianapolis 500 winner Al Unser against his friend and former boss, 1963 Indy 500 winner Parnelli Jones; and two-time winner Al Unser Jr. vs. three-time winner Johnny Rutherford.

Fans can vote for their #Champsofthe500 every hour during the contest by visiting ims.com/champsofthe500, and are encouraged to tout their votes by using the hashtag #Champsofthe500 in Facebook and Twitter posts. The voting contest runs in conjunction with Legends Day Honoring Champions of the 500 presented by Firestone at Indianapolis Motor Speedway on May 28.

In the first bracket showdowns that ended April 21, four-time Indianapolis 500 winner Foyt defeated two-time winner Juan Pablo Montoya and two-time winner Vukovich edged three-time winner Wilbur Shaw. Voting that ended April 24 featured all three-time race winners, with Castroneves (52.4 percent of the vote) topping Louis Meyer (47.6 percent) and Bobby Unser (74.6 percent) defeating Mauri Rose (25.4 percent).

The Round of 16 features a pair of bracket showdowns running three days each and concluding April 30. The eight winners by popular vote advance to the quarterfinal round, with the semifinals and championship round to follow. Show your Indianapolis 500 pride and vote for your #Champsofthe500.

#Champsofthe500 First-Round Pairings:

April 18-21: A.J. Foyt def. Juan Pablo Montoya; Bill Vukovich def. Wilbur Shaw

April 21-24: Helio Castroneves def. Louis Meyer; Bobby Unser def. Mauri Rose

April 24-27: Al Unser vs. Parnelli Jones; Al Unser Jr. vs. Johnny Rutherford

April 27-30: Rick Mears vs. Dan Wheldon; Mario Andretti vs. Dario Franchitti

Note: Voting begins and ends at noon ET on the designated days; drivers receiving the most votes in each pairing advance to the quarterfinal round to follow. Vote at ims.com/champsofthe500.