How Stock Car Racing Techniques Work

­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.

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Trading paint means coming so close to another car that, well, in a parking lot you'd have to leave a note on the person's windshield. (When you're traveling at 180 mph, however, stopping to leave a note is inadvisable.)

Why would you deliberately bump into another car or brush against it? Basically, because winning a race demands aggressive driving. We'll go into the techniques of bump drafting and bump-and-run on the next couple of pages. Rubbing the car next to you means giving that driver some friction to deal with -- probably making him (or her) slow down, and perhaps letting you get into a more advantageous position. Imagine a foot race in which the sprinters not only run at top speeds but also throw elbows at each other.

­It's possible to be too aggressive. Rising racing star Colin Braun was recently suspended for trading paint; he was already on probation for the same thing. He explains without apology: "I'm going to drive as hard as I can. Contact is always involved in racing, especially on the final lap" [source: Perez].

Is trading paint dangerous? Well, of course. Basically, you're causing minor car accidents on purpose, and at top speed on a crowded track, a minor car accident has the potential to become a major one in the blink of an eye.

The bottom line is, don't trade paint unless you're highly confident in your ability to control your own car. Even then, you have to gauge its appropriateness based on the track, the situation and the other drivers around you.

­Trading paint and drafting are techniques that involve what happens around the car. Another kind of technique is all about what happens inside the car. Read on.

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Inside or outside the car, the action in a race happens on the curves. Curves are the most likely locations for passing, and they're where drivers have to focus most on handling. Taking a curve well means slowing down on the approach and then accelerating smoothly and promptly out of it.

Now consider this: Many stock cars have manual transmissions. Slowing down or speeding up involve shifting gears. On the street, a driver might just push in the clutch for whole turn, but on the racecourse, that's a bad idea. When the clutch is engaged, the engine is idling. Getting back up to race speed will make the car buck, because the engine suddenly has to go from idling to thousands of RPMs. Bucking damages the clutch and transmission, and it makes the car harder to control [source: Romans]. Heel-and-toe downshifting is the solution.

Heel-and-toe technique is basically an intricate seated dance that helps the driver match engine RPMs to wheel speed. You can actually try it in a typical stick-shift street car. Here's how:

­In a stock car race, all that happens in less than a second. And it might happen while someone is rear-ending you -- on purpose. Continue reading to find out about the bump draft.

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Bump drafting may sound like a controversial army practice, but it's actually a controversial stock car racing practice. NASCAR veteran Kyle Perry calls it "positively, absolutely idiotic, period" [source: Borden]. Tony Stewart is equally blunt -- "Somebody else is going to die at Daytona or Talladega" -- and drivers such as Jeff Gordon have petitioned NASCAR to ban the practice [source: Bonkowski].

Other drivers see it as useful, even necessary. Bump drafting can be a way to liven up a very long race and, perhaps, improve your position in a long string of cars [source: Borden].

­So what is it? You already know what drafting is -- tailgating elevated to an art form. Now imagine pulling forward just enough to kiss the bumper of the car in front of you. Bump! That's a bump draft.

Executed correctly, a bump draft nudges the front car forward, which means you get pulled along in its wake. The whole line of cars behind you could gets pulled along as well. And the front car usually has to slow down in response to the bump. (Stock car racers aren't the only ones who use this technique -- police use it to slow down fleeing vehicles in high-speed chases.)

Bumps create opportunities for drivers to pass, breaking up the monotony of a hundred-lap race. But they can also be dangerous, especially for the car being bumped. Its rear wheels lose traction -- that's why the driver has to slow down. Bumps are also more dangerous for both cars on curves, when wheel traction is lower anyway. And some younger drivers bump so aggressively that the technique has been renamed slam drafting.

A bigger danger: The bumped car can go into a spin, and the risk is higher at typical racetrack speeds. If the front car winds up sideways, there's a whole line of cars in position to hit it, and that hit is going to be more than a little nudge. With several high-profile accidents and driver deaths in the past decade, it's no wonder stock car racers and fans are so passionate about bump drafting.

What happens after the bump? You run. Read on to find out how.

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The bump-and-run technique is an outgrowth of bump drafting. It works something like a pick-and-roll maneuver in basketball: Create an obstacle for your opponent so that you can get past him. A bump-and-run maneuver simply means that you bump the car in front of you, and then -- since he'll have to slow down in response -- you rev the engine and pass him at the next corner.

Bump-and-run is just as controversial as bump drafting. Many veteran NASCAR drivers want it banned, and NASCAR races now have no-bump zones.

­Part of the problem is the difference in car bumpers across different stock cars. As the name implies, it's a bumper's job to take a hit. Ideally, a good bumper minimizes or even prevents damage to the rest of the car.

Some stock car bumpers have enough give to make the bump relatively gentle. Others -- notably, those with front steel plates and rear reinforcement -- force all the impact onto the car being bumped [source: Pearce]. That essentially means the force of the hit is out of either driver's control.

In NASCAR, the introduction of the Car of Tomorrow means that all cars have standard bumper heights. That should reduce the danger involved in bumping and running. But on the rest of the stock car racing circuit, drivers and teams are still free to customize their vehicles. So until the moment you are hit, you don't actually know whether it's going to be a nudge or a disaster.

You can take a lesson from the pros, and soften your own bumpers to resemble those of the Car of Tomorrow. Apart from that, your best strategy is the same as it always is: Stay alert, know the track, know the car and drive smart.

To learn more about stock car racing, visit the links on the next page.