Jimmie Johnson talks to a crew member before practice for Sunday's NASCAR Sprint Cup series Coca-Cola 600 auto race at Charlotte Motor Speedway in Concord, N.C., Thursday, May 22, 2014. (AP Photo/Terry Renna)
Greg Biffle waits by his car before practice for Sunday's NASCAR Sprint Cup series Coca-Cola 600 auto race at Charlotte Motor Speedway in Concord, N.C., Thursday, May 22, 2014. (AP Photo/Mike McCarn)
Austin Dillon prepares before practice for Sunday's NASCAR Sprint Cup series Coca-Cola 600 auto race at Charlotte Motor Speedway in Concord, N.C., Thursday, May 22, 2014. (AP Photo/Mike McCarn)
Brian Vickers climbs into his car before practice for Sunday's NASCAR Sprint Cup series Coca-Cola 600 auto race at Charlotte Motor Speedway in Concord, N.C., Thursday, May 22, 2014. (AP Photo/Mike McCarn)
Kevin Harvick talks to a crew member before practice for Sunday's NASCAR Sprint Cup series Coca-Cola 600 auto race at Charlotte Motor Speedway in Concord, N.C., Thursday, May 22, 2014. (AP Photo/Terry Renna)
Matt Kenseth waits in his car before practice for Sunday's NASCAR Sprint Cup series Coca-Cola 600 auto race at Charlotte Motor Speedway in Concord, N.C., Thursday, May 22, 2014. (AP Photo/Terry Renna)
Brad Keselowski, center, signs autographs before practice for Sunday's NASCAR Sprint Cup series Coca-Cola 600 auto race at Charlotte Motor Speedway in Concord, N.C., Thursday, May 22, 2014. (AP Photo/Mike McCarn)
Jeff Gordon talks to crew members before practice for Sunday's NASCAR Sprint Cup series Coca-Cola 600 auto race at Charlotte Motor Speedway in Concord, N.C., Thursday, May 22, 2014. (AP Photo/Terry Renna)
Kyle Bushc, left, talks with Dale Earnhardt Jr, right, before practice for Sunday's NASCAR Sprint Cup series Coca-Cola 600 auto race at Charlotte Motor Speedway in Concord, N.C., Thursday, May 22, 2014. (AP Photo/Mike McCarn)
Jimmie Johnson prepares before practice for Sunday's NASCAR Sprint Cup series Coca-Cola 600 auto race at Charlotte Motor Speedway in Concord, N.C., Thursday, May 22, 2014. (AP Photo/Mike McCarn)