Stock Car Aerodynamics - Bad Air?

When you come right down to it, auto racing is applied physics. At roughly 200 mph down the straight at Daytona International Speedway, a Winston Cup car is a melding of thermodynamics and aerodynamics, each science in conflict and concert with the other.

For decades, thermodynamics ruled. Success on a racetrack could be predicted by whichever driver had the most power under the hood. But today, thanks to NASCAR's restrictions and rules tending, there is less horsepower difference from one engine to another, from the pole to the 43rd starting spot, on any given Sunday, no matter what it may say on the valve covers.

Faced with not being able to build a dominating engine, teams began experimenting with how to build a better package around it. Starting with what were once stock cars, the factories began to massage bodywork or build special editions such as the Ford Talladega and the winged Dodge Daytona and Plymouth Superbird to gain an aerodynamic edge. Those cars marked the first skirmishes in what was to become the aero wars of today.

"I was among the first crew chiefs to take a car to a wind tunnel," recalls Gary Nelson, now head of NASCAR's technical development team. "We didn't know what to look for. We weren't even sure what aerodynamics were. We just knew they were important.

"One of the things we recognized was that if a car could go 100 mph with the engine it was allowed, that in order to make it go 200 mph we needed four times the power. We worked all season long to gain five or six horsepower, so we figured that in order to go faster we had to reduce aerodynamic drag," Nelson says. "But it was all such a mystery. You couldn't see air, so it was hard to figure out what to do with it."

When NASCAR began to allow full tube frame cars, the aero battle was joined in full and the giant fans on wind tunnels from coast to coast began spinning. The result was a nip here, a tuck there, maybe just a tad of a curve someplace else. Speeds went up, but handling on big tracks became lethal.

Then, teams discovered they could also use air to help plant the nose. Soon the shape of cars-refined in $2,000-an-hour wind tunnels built for the aircraft industry-became just as important as horsepower.

NASCAR asks manufacturers to design racing bodies that look uniquely different while, under the paint job and decals, are almost identical. And just like you should have learned in high school physics, for every action there is an equal and opposite reaction.

Ask the fans how they compare today's racing to the pre-aero era, and many will say they love the close on-track competition, but feel parity has left the cars circling speedways like a long string of colored pearls. Drivers feel much the same way. The term "aero push" is part of every driver's vocabulary. It's the loss of downforce on the nose of the car. It lightens the force on the front tires and allows them to head for the outside wall in a turn.

Aero push isn't anything new; it is just that today there is a name for it. Now NASCAR apparently is stuck with it.

Geoff Gray has spent time both in the grandstands and the driver's seat, racing everything from delicate sports cars to hefty trucks.

"As a fan, I think the aerodynamic parity has created much closer racing," he says. "The quality of the entertainment keeps fans on the edge of their seats. Twenty years ago you might see two or three drivers together on the track. Now, most of the field is in the same pack."

Still, the Midwest race fan says he would like to see NASCAR find a way to bring more passing to the sport.

"From the fans' standpoint, racing isn't as good as it used to be," says Terry Rabone, who has gone to every race at California Speedway since Winston Cup first began using it as a West Coast stop. "All you hear from the stands is 'aero push, aero push.'"