Drafting strategy involves more than simply knowing where to place your car on the track, and it often has less to do with aerodynamics and more to do with driver's knowledge of the competition's mind. Drafting strategy is where a race becomes a mental challenge as well as a battle of speed and guts. The lead driver can step on the brakes, come within inches of the following driver, and deprive them of the air needed to cool the engine. And just like that, one competitor goes down. The following driver can also pull a similar tactic, inching up on the car ahead in order to disrupt the flow of air over the lead car's body. Remember, that airflow is critical for keeping the lead car's tires stuck to the track surface. Without it, and maybe with a little help in the form of a bump, the lead car can lose traction, skid into an outside lane and quickly drop 10 places (or more) during a race. Teams, sometimes official but often an informal collaboration, use the power of drafting to rocket members past the competition, vie for the best track real estate and even steal the race lead at a moment's notice. All's fair, it seems, in love, war and drafting.
The two-car draft is the most basic draft pattern and the one most often used by a team. Pulling within a car length of a lead car benefits the trailing car by reducing drag. That same reduction also benefits the lead car as the presence of the trailing car reduces the pressure drag off the back of the lead car. The result is a speed increase for both drivers.
Brett Bodine, now the director of cost research for NASCAR's Research and Development Center, began his career as a NASCAR Truck Series driver. He said the drag created by the boxy truck designs, as well as less horsepower than Cup Series vehicles, put drafting at the top of the strategy list.
"You see two cars side-by-side, you know there's a big hole behind them and if you can get in that you can accelerate faster," Bodine said, adding that, in the truck series, the vehicles punch bigger holes in the air, allowing for even more acceleration in the draft position. "When you see that, you have to start planning your moves, take advantage of what's being offered."
As you may have guessed, the more cars involved in a draft the less drag each vehicle will experience. Bodine has seen and experienced this phenomenon, firsthand. "Three cars will run faster than two, and five cars will run faster than three," he said. This is why cars often run in drafting packs and lines, each gaining a few more miles per hour from the car in front and behind as pressure drag is reduced. This can have a profound effect on the overall running of a race.
Bodine also said lead drivers often shift from one drafting lane to another as need dictates. Whatever lane they lead will go just a little faster than the one they just left. "This is especially true at tracks like Talladega," Bodine said. "You'll see a guy at Talladega moving around and you know that whatever line he gets in front of moves faster."
And if a driver makes a mistake and falls out of the drafting line it could spell doom for their chances in the race. "If you fall out of that line, if you have to go to the pits for a problem, you're probably going to get lapped," Bodine said.
The basic physics of the draft -- from the two-car draft to draft lines -- can be used by teams to accelerate their drivers or stall the competition by depriving them of reduced pressure drag. But it's not so simple streaking down the track at nosebleed speeds. Bodine said the days of practice leading up to a race allow each driver to get to know the other cars. "You want to know exactly what your car can do on the track every second of the race," he said. "You want to know who you can draft behind, what your car will do in the curves and stretches, and how it will react. There should be no surprises."
This means finding the sweet spots on a potential lead car's bumper for the draft, and in more advanced driving situations where to place your car in front of or behind another car to deprive them of downforce, increase their drag, or even rob them of an opportunity to pass.
If you think you've heard it all, well then you'd better get ready for the next page. That's where we take a look at the more "sophisticated" side of drafting.