PUSHING THE ENVELOPE

To hasten the development of the new Gen-6 race cars, it's important for race teams to test the limits of their capabilities. Robin Pemberton, NASCAR's vice president of competition, says the sanctioning body is pleased with the teams' willingness to do just that.

"We expect the teams to continue to push the limits of their equipment, and that's what important," Pemberton said after the first session of practice at Las Vegas. "I think early on there were concerns over reliability on parts and pieces, because we've pushed the envelope out there with cambers and things of that nature, the rear-end housing… the left-front camber maximum was increased.

"So it's up to the teams to continue to push and make their cars drive the best that they can. So far, everyone seems to be doing their job. Speeds are right in the range that we expected to see for the first day."

In fact, speeds increased throughout the sessions, with Greg Biffle posting the day's fastest lap (189.427 mph) late in Thursday's second practice. Kasey Kahne's track qualifying record from March 2012 is 190.456 mph.