The premise of drafting itself is simple. Two or more cars/trucks racing along on a track of any size will follow each other around the speedway as if one is tied to the rear bumper. Why? The draft. The vehicle in front punches a hole in the air as it moves, roiling the air as it passes over, around, and through the vehicle in front of it. The second vehicle in line, by staying directly behind the leader, can use a principle of fluid dynamics—the vacuum—to “suck” along behind the lead vehicle, thus saving fuel and wear and tear on the engine and other components.

Despite that relatively straightforward explanation, NASCAR Winston Cup driver Ricky Rudd put it in plainer terms: “Basically, you take two cars that can run 190 mph by themselves, but nose-to-tail they can run 200 mph,” Rudd says. “It’s sort of cheating the air. When you put two cars together, you reduce the drag tremendously, therefore the cars will run quicker together.”

Let’s begin with a solo car, if a car is on the track by itself, there’s pressure on the front because of the air flowing over the front of the car. There’s air pressure over the top, bottom, and back, which is caused by the flow of air over the car. If you have two cars nose to tail, then it changes the airflow and the resulting pressure on both of them. Visually, you can imagine the turbulent wake of air coming off the first car, and that changes the airflow on the car behind dramatically.

There is no longer the smooth streamline of high-speed air over the nose of the car behind. The airflow still pretty much goes over the top of the second car and down to hit the spoiler, so the rear down force is not a lot different, but the front down force and drag are very different on the car that’s behind. There’s much, much less drag.

The car that’s in front also has a different airflow—it is still about the same. The airflow over the back is very different because of the car behind. It backpressures the airflow over the roof of the front car so it may or may not hit the spoiler. Both cars have less drag, the front car has less rear down force, and in the rear car, the front down force is much more variable. Both cars have a lot less drag, and the down force—the down force balance front to back—is very different.”

Stay In Line!!!!

If I had to explain drafting, the first thing I would say is that what you see on the in-car cameras on television doesn’t do it justice. None whatsoever. In simple terms, the car in front opens a big hole in the air. The car behind him is in a void, so it has no resistance to the front end of the car, and that makes the car feel like it’ll run faster. It will run faster until you pull out and hit the air.

1. The art of drafting is a complex science, but to the race fan it can be as simple as one, two, three. For example, this graphic demonstrates what can happen to an eager driver who is in a tight draft. Graphic one shows the tight draft on a track like Talladega or Daytona.

2. Graphic two shows the second car in line (green car) stepping out in an attempt to pass the first car. Problem is, that unless others go with him, it will lead to graphic three, which results in the cars behind the leader closing the gap.

3. When the gap is closed, as illustrated in graphic three, the eager driver (green car) has been hung out to dry, which results in the draft train passing him and shuffling him to the back of the pack. If, on the other hand, the green car stepped out and had help, then the leader (red car) would be the one shuffled to the back of the pack.

OK, now that we have a working definition of drafting and how is it used. Why is the “slingshot” move, seen at many thrilling races at Daytona and Talladega, important? The slingshot procedure at Daytona is a good example of how drafting can affect your performance. The slingshot is when the second car is higher on the track than the lead car and gets a lot of momentum and speed.

It then gains more momentum and speed by gradually making a left turn and going through the wake of the first car and has even less drag. He/she then pulls to the bottom of the track and passes (zooms by) the lead car. What’s going on there aerodynamically is that the slingshot car is acting like a solo car when it’s up high. It has much less drag, and it’s also going downhill. This is almost always done in the corners so that it has a lot less drag when it passes the wake of the first car. It also has enough momentum to go ahead and pass the first car.”

Got all that? The slingshot is simply a matter of taking the air and using it to your advantage. That’s the essence of drafting—using every scrap of air to get past the driver in front of you. Horsepower becomes a slave to physics, and using the draft well can mean as much as a whole tank full of nitrous oxide when it comes to short bursts of speed.

Any Secrets?

OK, now that we’ve established what the draft is and how it can be applied, let’s ask another question: Is there a big secret to it? It’s an invisible wave. It’s not just riding that wave and taking advantage of it; it is knowing how to use it to your advantage, knowing how to change the handling on your car. If you ride on the inside or outside of the guy in front of you, you change the handling on your car. You also change the way the guy in front of you handles.
The key to drafting is to watch and learn. “To race well at any race track, you have to learn to read the car in front of you or what the air is doing—if there is such a thing as the vision of air. You can’t see air—that’s the first thing—but it’s there. You can feel it, and you can feel what it does to the race vehicle. You can watch the tachometer and see an improvement. What you do is pay attention to what your vehicle is doing and what the other car is doing.
So that’s the draft, ladies and gentlemen. It’s air as a tool to win races, and it is both simple and complex. Remember, two cars or trucks together have less drag than one alone, and it’s all a project of making the wind work for you, not against. This will send you to the winner’s circle on race day!!

Alex George / Assistant Engineer / Team West-Tec
"Rubbing is racing, get over it!"

A big thank you to Alex for giving us permission to reproduce his oval racing articles, Alex has been involed with Oval racing since 1983 when we was a mechanic with Firestone, and has working on sprint cars as well as other cars used on oval circuits across America, since 2001 Alex was worked as a assistant engineer with Team West-Tec the Ascar racing team based near Rockingham Motor Speedway.