Six Sprint Cup Series drivers, including Jimmie Johnson, have gone to back-up cars after crashes in Wednesday's practice sessions at Daytona International Speedway.

Clint Bowyer and David Reutimann were in an accident in the first practice. Bowyer blew a tyre and clipped Reutimann, who was then hit from behind by Derrike Cope.

Bowyer and Reutimann will have to go to the rear of the field in their Gatorade Duel races Thursday that set the line-up for Sunday's Daytona 500. As long as they don't change cars after the qualifying races, they can start the Daytona 500 where they qualify Thursday.

Unlike Reutimann and Bowyer, Cope does not have a guaranteed spot in the 500 field and must qualify for the race on speed Thursday.

Matt Kenseth led the practice session with a speed of 194.254 mph. He was followed by Kyle Busch, Brian Vickers, Jeff Burton and Carl Edwards.

In the second practice, Mike Bliss spun into Joey Logano, and Johnson and Denny Hamlin were collected in the accident. Only the damage to Hamlin's car was minor enough for him to avoid going to a backup car.

"There was nowhere to go," Logano said. "When you see a car get loose like that, you pretty much throttle down and hope you avoid it. I just didn't make it."

Johnson, Logano and Bliss will start at the rear of the field in the Duels. They will be allowed to keep their starting positions for the 500 that they earn Thursday.

The fastest in the final practice was Marcos Ambrose, who turned a lap of 193.403 mph. Busch, Reed Sorenson, Logano and Kenseth rounded out the top five.

Meanwhile Nationwide Series practice had no accidents during its two-hour session Wednesday, just a lot of attention on rookie Danica Patrick. Patrick finished 26th in the drafting practice.

Fastest was Tony Stewart, who posted a speed of 184.695 mph. The rest of the top five were Scott Lagasse Jr., Bliss, Steve Wallace and Greg Biffle.

by Sporting News / NASCAR Wire Service