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How does downforce help a NASCAR race car?

Maximum Downforce
It's easy to see how low the splitter is on Jimmie Johnson's #48 car -- the bottom edge is neon green.
It's easy to see how low the splitter is on Jimmie Johnson's #48 car -- the bottom edge is neon green.
Harry How/­Getty Images

­Drivers always say they want more downforce in the turns. What that really means is they want maximum stickiness in the corners and minimum drag on the straights. That's difficult to do -- especially when the adjustments teams are allowed to make the NASCAR Sprint Cup body are so minor.

There are, however, a few fine tuning adjustments the teams can make, like adjusting the angle of the rear spoiler. The steeper the angle of the rear wing, the more downforce it can add to the rear end of the car. This is what keeps the rear tires firmly planted on the pavement. At the front end, a piece called a "splitter" performs a similar role to keep the front wheels stuck to the ground. The splitter is the component that you see at the leading edge of a NASCAR race car. It runs the full width of the car, is adjustable and often appears as if it's low enough to scrape the track surface.

There are times when teams choose to go for as much downforce as possible. For instance, on road-courses with plenty of turns and very few long, straight sections of track. By making slight changes to the rear wing and the front splitter, downforce can be maximized, increasing the car's grip in the turns.

­But the majority of races in the NASCAR schedule are on high-sped oval tracks. So, we're back to our question of how to balance downforce and drag. Drafting can help. Drafting on the track allows the vehicle following the lead car to lessen its drag. The air flowing over the front car carries right over the windshield and roof of the second car, too. That's great for the second car and any car that happens to be drafting behind it, but what does the lead car get out of all of this? The lead car in a drafting pair gets something out of the maneuver, too. The second car cuts down on the pressure drag of the front car. You can think of pressure drag as a low pressure wake left behind by the car as it speeds along the track. This type of wake, however, actually pulls the vehicle backwards. By eliminating the pressure drag on the lead car, the two drafting cars can gain up to a 5 mph (8 km/h) advantage over a car turning laps solo [source: Schirber].

­Once the little tweaks for just the right amount of downforce have been made, the driver has a good feel for the race car (and the track) and maybe even practiced his drafting skills, there's really only one way to take full advantage of the aerodynamics during the race: Don't crash. That's logical advice, right? When each NASCAR Sprint Cup team has made the tiniest of adjustments to the vehicle's aerodynamics in an effort to gain an advantage of just a few hundredths of a second per lap, something as small as a crumpled front corner can end their hopes for a victory on that day.