Stock Car Drafting
Like so many other good things, drafting was discovered accidentally by a moonshiner.
Junior Johnson went from narrow escapes from the feds to narrow escapes from fellow stock-car racers. He noticed that whenever he got right behind another car, he was able to go faster. He suspected the front car lowered wind resistance for the back car by "creating a situation, a slipstream kind of thing." His technique helped him win the 1960 Daytona 500, even though his car was slower than some other cars on the track [source: Tierney].
Other drivers began imitating Johnson's technique, and drafting was born. Stock car racing went from a combination of luck and horsepower to an intensely technological, strategic sport.
What actually happens in drafting? There's a sort of aerodynamic symbiosis at work. It begins when the trailing car gets within inches of the front car's rear bumper. The front car creates a low-pressure area -- a draft -- that essentially acts like a vacuum and pulls the back car forward.
Doesn't that make the back car more of a parasite? Not quite. The back car is so close to the front car that it reduces turbulence for the front car. Just like on an airplane, turbulence happens when powerful rotational (that is, nonlinear) currents of air buffet the vehicle and interfere with its maneuverability [source: Leslie-Pelecky].
The combined effects of drafting mean that a pair of cars driving one behind the other can go as much as five miles per hour (about eight kph) faster than either car driving alone. Add another car behind the trailing car, and the effects get even more pronounced [source: Tierney]. Drafting is the reason so many stock car races turn into long lines of cars circling the track in close formation. You're less likely to see drafting in short-track races, however, as the shorter track reduces the advantage of its effects.
Obviously, whenever two speeding vehicles are separated by mere inches, drivers must be incredibly precise. To draft, you have to know and trust your car's handling. And if you want to change your position in the line of cars, you have to be strategic. On the next pages, we'll look at some of the strategies -- heel and toe racing, bumping, and bumping and running.