INDIANAPOLIS -- With straightaways only 50 feet wide and turns banked at fewer than 10 degrees, negotiating the venerable Indianapolis Motor Speedway's ribbon-like asphalt at speed is already the perfect recipe for single-file racing. But add to that the turbulence from running directly behind another car, and it compounds the problem of passing.

Greg Biffle felt it first-hand near the conclusion of Sunday's Brickyard 400.

“

These race cars are hard to pass on this track. It seemed like the guy that got out front had a big advantage and we needed to be out front.

”

-- GREG BIFFLE

With four fresh tires, Biffle may have had the fastest car on the track over the final 15 laps. But stuck behind eventual winner Jamie McMurray and second-place Kevin Harvick, "dirty air" did in any chance Biffle had of getting to the front.

While McMurray was running without turbulence, Biffle was struggling with the aerodynamic effects caused by the rear spoiler, used for the first time Sunday on NASCAR's current chassis design at Indianapolis.

"It's really unbelievable, the difference," Biffle said. "It's like you've got brand-new tires when you're out front and like you've got 20-lap tires when you're six car-lengths behind a guy. The thing just stops. It just slides all four tires.

"I was behind Kevin and just sliding the front and sliding the back right up against the fence and I just couldn't get the gas down. I just couldn't get enough of a run to get to him."

Jimmie Johnson wasn't a factor after handling problems put him well back in the field, but he also noticed how hard it was to pass cars all day.

"My car wasn't driving right, so it's tough to say, "Johnson said. "But I didn't see many people moving forward. You'd get one or two positions and that was it. I think it's more difficult to pass with the spoiler just because there's no air coming below the wing like we used to have. The spoiler just kicks the air higher and it makes a bigger hole behind the car."

How critical was track position? Of the six cars which opted for two tires on their final pit stops, none finished worse than 11th. Track position directly figured into the decision made by McMurray and crew chief Kevin Manion to take only two tires on their final pit stop, although McMurray was kicking himself for what he felt was a poor restart that allowed Harvick to edge back in front just as the final caution came out on Lap 147.

"When I got out in front, I honestly didn't think anybody would catch me," McMurray said. "[Harvick] hadn't been as good as us all day. I thought I'd be able to drive away from him. I got really tight. Kevin got up underneath me. I kind of let him go because I was going to try to cross over going into [Turn 1].

"As soon as I let off the gas, the caution came out. I was pretty frustrated." (Continued)