Stock Car Aerodynamics - Bad Air?

Gray says NASCAR needs to do less tinkering with the rules once it waves the first green flag of the season. "I know they want tight racing, but NASCAR should set the rules before Daytona and stick with them," he says. "If a manufacturer made a mistake and built a car that isn't as good as the rest, well they have a year to figure it out and make it right for next season," Gray says.

NASCAR got itself into the aerodynamics business because of parity and manufacturer politics. It wanted to find a way to make the on-track performance of each brand of car near equal.

"One of the problems we had was that as cars evolved, they began to change an awful lot," NASCAR's Nelson says. "They each had about the same size engine, but one may have had a much longer hood over it and another had a longer wheelbase. There was so much difference between a Chevy and Ford that we had to keep adjusting the specifications. Then, when they went to front-wheel-drive cars, it became a moving target. It was almost impossible to keep up."

NASCAR increased its control over the shape of its cars and began to get serious about aerodynamics just about the time its teams discovered the advantages of hours spent in wind tunnels coming up with even a tiny improvement.

"NASCAR calls what it has today 'aerodynamic parity,'" says an industry insider. Teams, drivers, and knowing fans call it "common body templates."

"The new Dodge was built using the 2000 Taurus body templates," the insider says. Changes were allowed in the front and rear bumpers and enough variation was allowed on the hood to make it look like a Dodge and not a Ford. The bodies are so close that Ford supplied Taurus sheetmetal to Dodge teams during Chrysler Corp.'s first year back in Winston Cup. Like the Dodge, the next generation Pontiac is based off the Taurus templates.

The industry source says manufacturers at first lobbied against adopting similar body shapes but eventually realized NASCAR wasn't going to back down on the issue.

"Each template is unique," Nelson says. "You can still tell a Dodge from a Pontiac. But yes, they are all very similar."

Right now the quarter-windows are still free for teams to tinker with, but NASCAR is developing its own "greenhouse" specifications that may curb even that bit of variation. The larger greenhouse is being developed chiefly in response to drivers who say the downsizing of today's cars-coupled with more safety gear inside the race cars-makes it difficult to get out in an emergency. But just like a thicker wing on an airplane produces more lift, a larger greenhouse on a race chassis reduces downforce going to the tires. Late-season testing of cars with the new greenhouse showed them the need for more work before the 2003 season begins.

Just like the engines for each track require a unique camshaft and intake and exhaust configuration, the aerodynamic needs also differ.

"At Martinsville you are looking more for mechanical grip. It doesn't matter if the car is rolled over or if the left-front valance is on the ground," says Elliott Sadler, who drove the Motorcraft Ford for Wood Brothers Racing in 2002.

"But at places like Michigan, Indy, and Charlotte, you need to keep the attitude of the car right, to not only get mechanical grip but to get aero grip to try to take care of the push that you hear so much about," Sadler explains. "You want to keep the left-front fender on the ground ... and keep the car as flat as you can."

Sadler says it's tough to describe what "aero push" feels like. "It's nothing that you will feel on an ordinary car. It is like somebody has two jacks under the car and is lifting it off the ground and making it push. No matter which way you turn, it doesn't matter. It's just going to slide."

Kurt Busch, who drives the No. 97 Rubbermaid car for Roush Racing, says the effects of aerodynamics on passing are compounded by tires that last so long cars can run the low groove lap after lap, eliminating one of the chief areas for passing on many ovals.