Louis Meyer and Helio Castroneves

The next two first-round matchups in the "Champions of the 500" bracket challenge is open for voting. Vote between now and noon ET April 24 to determine who will join A.J. Foyt and Bill Vukovich in the quarterfinal round.

Sixteen of the greatest Indianapolis 500 winners – legendary names ranging from Shaw to Montoya, Rutherford to Franchitti – 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. In the first bracket showdowns that began April 18 and ended earlier today, Foyt, the four-time Indianapolis 500 winner, received 83.4 percent of the votes to defeat two-time winner Juan Pablo Montoya, who had 16.6 percent, and two-time winner Bill Vukovich edged three-time winner Wilbur Shaw, 55.5-44.5 percent.

The current pairings up for vote consist of all three-time winners: Helio Castroneves vs. Louis Meyer and Mauri Rose vs. Bobby Unser.

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.

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 vs. Louis Meyer; Mauri Rose vs. Bobby Unser

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.