DIRTY AIR

When a car goes through the air it leaves a wake. Think of a motor boat on a lake. At certain points the wake is smooth. At other points it is boiling like a Jacuzzi tub. Dirty air does funny things to the handling of the other race cars close by. (See DRAFTING)

DOWNFORCE

The air pressure traveling over the surfaces of a race car creates "downforce" which pushes the car into the racetrack giving the tires more grip. The problem with downforce is that it creates "drag" (think anchor) which makes the engine work harder and slows the car down. Here again it is all about balance.

DRAFT

The aerodynamic effect that allows two or more cars traveling nose-to-tail to run faster than a single car. At a superspeedway like Daytona or Talladega a driver can never run as fast alone as he can with other cars.

DRAFTING

The practice of two or more cars, while racing, to run nose-to-tail, almost touching. The lead car, by displacing the air in front of it, creates a vacuum between its rear end and the nose of the following car, actually pulling the second car along with it. Sometimes the driver in the second or third car will actually have to lift his foot off the gas to keep from hitting the car in front. A driver has to deal with several problems when running the draft. Because the following car is running in a vacuum there is not much air flow over the radiator and the engines have a tendency to overheat. That is why you will see drivers sometimes ducking in and out when they follow each other real close. By the way "Bump Drafting" is when a driver allows his car to run right up on the car in front and give him a solid push by slamming into his back bumper. This increases the speed of both cars. It is not a good thing to "bump draft" in the corner because it might cause the lead driver to loose control.

DRAG

The resistance a car experiences when passing through air.