In 2007, Alan Gustafson and his fellow Hendrick crew chiefs made racing the car of tomorrow look easy. The Gustafson-led No. 5 crew won the first-ever COT race at Bristol, while the No. 48 and No. 24 teams won seven of the season’s 15 remaining COT events. But no matter how well last year might have gone, the No. 5 team is still getting to know this car, and, in particular, the splitter.

“Going from the valence on the old car to the splitter was a huge shift aerodynamically,” Gustafson says.

So, what’s the big deal?

Essentially, the combination of new rules and a new nose has changed the way cars produce downforce.

“In the old cars, there were no rules about what kind of springs you could run up front, so we’d use real soft springs and build the cars to get a lot of travel,” says Murray Timm, fabricator for the No. 5 team. “That puts attitude in the car where the nose is down and the back is up. The more attitude we added, the more downforce the car produced.

“With these cars, they [NASCAR] mandate springs and heights and took the travel out. So the splitter is the only thing left that produces downforce.”

Teams can adjust the splitter — pushing it fore and aft or skewing it so one side sticks out further than the other — all within NASCAR’s regulations, of course — but chasing the splitter is an exercise in diminishing returns.

 “The longer it is, the more area for high-pressure air, which creates more downforce,” Gustafson says. “But what that leads to is teams running at maximum length almost all the time. Everyone will run it as long as possible at the intermediate tracks and short tracks. At superspeedways, you’ll see some, but not all, cars at minimum.”

The No. 5 team might run most races with the splitter sticking out six inches but the team will tweak it over the course of a race weekend.

“We’ll run a very short splitter for qualifying trim,” Gustafson says, “but then we’ll slide them back out.”

The jutting shelf has impacted more than just the car’s handling, the No. 5 team has had to tweak its pit stops.

“The biggest thing we’ve had to adjust is the front tire changer’s routine,” Gustafson says. “You’ve got to be really careful not to catch your hose on that thing. As you watch the tire changer come around the front end, they do a dramatic whip of the gun and if you don’t know, it may look like it’s just for show. What they’re trying to do is give the hose enough slack to go around the nose without getting stuck.

“Then, when he gets up to come back, we have someone behind the wall who pulls that slack back out of the hose so it won’t snag.”

The row of turnbuckles on the splitter has also forced the team to take a new approach to keeping the grille clean.

“On the Monte Carlo, we’d have the tire carrier swipe the grille as he came by,” Gustafson says. “Now, we have splitter rods in front of the grille so there’s no easy way to get to it. Most of the time, the tire carrier can’t even try to brush it off because he could get his hand stuck. And that would be bad for everyone.”

Consequently, Gustafson and his crew have had to learn to be more tolerant of trash on the grille.

“That’s one reason why we run a sloped opening. We try to get the high-pressure air on there so the trash will just fall away,” he says.

“Also, we can’t run our tape as tight initially because we have to allow for more trash build-up.”

While the pit crew reworks its routines, the drivers also have a few more things to keep in mind. In addition to the alien handling of the new car, Gustafson has learned to remind drivers to be more careful getting on and off the track.

“At Bristol and Dover, you really need to watch the transitions. The driver has to be more conscious,” he says. “Coming into pit road, they need to be careful to ease down the transition. Road-courses are hard, the curbs have bent some of the struts on the splitter. Really, we just have to remind the driver to stay cool and take care of the car.

“If you’re at Daytona and a big wreck happens, Casey [Mears, driver of the No. 5 in 2008] may need to dive down to the apron, and that could potentially damage the splitter,” he says. “And if the splitter fails, you lose more of your front downforce. You can’t be competitive without it.”

With that in mind, the No. 5 team comes to every track with a full complement of extra splitters.

“We bring three to five a weekend,” he says. “That’s probably too many, but it’s better to be ready for the worst-case scenario. We’ll take six splitters to Daytona testing. If everything goes well, we’ll use two a weekend — one for practice and one for the race.”

This article first appeared in the March 2008 issue of NASCAR Illustrated.