The addition of a VHT traction compound worked in the bottom lane on the concrete surface at Bristol Motor Speedway.

But the use of the TrackBite in the top lane on the asphalt at Charlotte Motor Speedway remains an unknown, as the track tries to widen the groove to give drivers racing options for Sunday’s Coca-Cola 600 on FOX at 6 pm ET.

“We’ll find out,” said Ryan Blaney, driver of the No. 21 Wood Brothers Ford Fusion. “It’s kind of uncharted waters, to be honest with you.  Bristol is a lot different, a lot shorter race track, we’re not going as fast… a concrete race track. You don’t know how that substance they use is going to combine with asphalt. I’m curious to see how that does, and it’s very heat-activated.

“At Bristol, we’re going to be running the bottom regardless. That’s why it worked so well on the bottom there, and here I’m wondering what it’s going to be like when we’re running 200 miles an hour into the top lane (at Charlotte) and hoping it’s hot enough to stick. So that’s going to be a little sketchy at first, but, like I said before, I thought NASCAR had to make a move on that side of it to get us off the bottom of the race track or at least give us options.”

In Thursday’s opening practice, where teams were concentrating on preparation for qualifying later in the day, no one ventured into the top lane—at least not on purpose. Trying to run the bottom, Kyle Larson inexplicably pushed up into the outside wall when his car tightened up.

Larson’s No. 42 Chip Ganassi Racing Chevrolet SS bounced off the SAFER barrier, damaging the right side of the car but not enough to require a backup Chevy.

Dale Earnhardt Jr. also got into the VHT sealer, but not by design.

“I got into it by accident,” said Earnhardt, whose No. 88 Chevrolet SS slid up the track. Earnhardt, however, made a nice save and kept the car off the wall.

Drivers should learn a lot more during Saturday’s two practice sessions, when they start running the outside groove on purpose.