The battle rages on in the semifinals of the #ChampsOfThe500 bracket challenge, with voting to decide the championship finalists concluding at noon ET Friday.

Sixteen legendary Indianapolis 500 winners were initially selected to square off in the 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. Fans can vote for their #ChampsOfThe500 once an hour while each pairing is open by visiting ims.com/champsofthe500. 

Drivers competing in the semifinals include the only four-time winners in Indianapolis 500 Mile Race history – A.J. Foyt, Al Unser and Rick Mears – and the only one entered in this year's race who could join the elite four-timers club, Helio Castroneves. The pairings pit Foyt against Castroneves and Unser against Mears.

Fans can vote each hour 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 semifinal survivors advance to the championship round of voting that begins May 16. Show your Indianapolis 500 pride and vote hourly for your #ChampsOfThe500.

#ChampsOfThe500 Semifinal Pairings:

May 9-13: A.J. Foyt vs. Helio Castroneves; Al Unser vs. Rick Mears

Note: Voting ends at noon ET May 13. The driver receiving the most votes in each pairing advances to the championship round. Vote at ims.com/champsofthe500.