Jimmie Johnson led both practice sessions today for Sunday's Pennsylvania 500 at Pocono Raceway, turning in a speed of 167.292 mph to top the charts in the first practice session. Johnson led happy hour with a speed of 165.795.

NASCAR Sprint Cup Series point leader Tony Stewart wrecked on the second lap of the first practice, forcing the Stewart Haas Racing team to take out it's backup car. The two time champion will now start from the rear of the field on Sunday.

Stewart experienced similar circumstances before winning the Pocono 500 in June. He was scheduled to start from the pole after qualifying was rained out, then wrecked his primary car in practice.

"I screwed up," Stewart said after the incident this morning. "I got in too deep and got loose and couldn't save it. I tore up a really good race car today."

Kevin Harvick, Mark Martin, A.J. Allmendinger and Dale Earnhardt, Jr. placed second through fifth fastest in the final practice.

The Pocono 500 is slated to take the green flag at 2 p.m. ET tomorrow.

 Sunoco Red Cross Pennsylvania 500 Practice 2

 Sunoco Red Cross Pennsylvania 500 Final Practice

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