Cup car's wing has a downforce to be reckoned with

NASCAR teams are still figuring out how to deal with the change from a spoiler to a wing on the back of the new Sprint Cup car.

Updated: July 26, 2008, 8:34 PM ET
By Bill Borden | Special to ESPN.com

Jimmie JohnsonGetty ImagesThe rear wing has created new challenges after teams thought they had the spoiler on the old car, right, figured out.
A lot of derogatory remarks have been made by some of the older racers in NASCAR about the rear wing that has replaced the spoiler on the Sprint Cup car. The negative remarks have been mostly related to the new "look" of the wing versus the old spoiler and do not consider the difference in performance the wing has brought to the sport.

The first question that arises in my mind is whether the wing is better or worse than the spoiler from an aerodynamic standpoint. To answer that question I contacted one of NASCAR's more noted experts on aerodynamics -- Bernie Marcus who is an aerodynamicist for Ford Motor Co. Bernie has an extensive background in aerodynamics with a variety of racing series from sports car and Formula One racing in Europe to Indy cars, drag racing and stock car racing in the United States.

Marcus said the wing is far superior to the spoiler when it comes to aerodynamic performance. He said the spoiler is a somewhat crude device that is used to create increased downforce on the rear of a race car but it also creates additional drag and it produces a lot of dirty air behind the race car. The dirty air created by a leading car will cause the front end of a trailing car to wash out [push] because the disruptive air flow will cause a loss in aerodynamic downforce. The spoiler got its name because it "spoils" the normal air flow over the deck lid and behind a race car.

If you have ever followed an 18-wheeler at a close distance on the interstate and were buffeted around by the swirling winds coming off the back of it then you have experienced "dirty air." While the dirty air coming off the back of a single race car would not be as severe as the air coming from a semi trailer, it would magnify exponentially when more cars and greater speeds are added to the mix. If you have ever stood near the fence at a super speedway when the pack of 40-plus cars roared by at full speed then you understand dirty air.

[+] EnlargeDraft Track
ESPNESPN's Draft Track technology, shown during broadcasts last year, illustrates how dirty air affects a trailing car.
A properly designed wing is more efficient in creating downforce while reducing related drag and does not create nearly as much dirty air behind the car. But we have heard drivers complain about a loss of front end downforce with the new Sprint Cup car when they are following another car into the corner. That would seem to contradict the science until you realize the new car creates less downforce compared with the old car, so you cannot make an apples to apples comparison.

Another factor that influences the comparative effectiveness of the wing on the new car versus the spoiler on the old car is that the "greenhouse" or passenger area of the new car is taller and wider than the old car, reducing the amount of air that can flow over the wing. This restricts the ability of the wing to create added downforce on the new car. It has been designed to do that by NASCAR because they wanted to create a specific amount of downforce for the new car that would make it more difficult to drive and therefore make the driver a more important part of the equation.

NASCAR partially addressed the difference between the two cars by adding small vertical fins to each end of the wing to aid in stabilizing the cars. These fins act much like the rudder on an airplane and help to guide the car through the corners.

Marcus said the vertical fins can be either flat or curved in shape to provide some amount of adjustment for the teams. Most teams run the curved fin on the right side of the car because it helps to generate more downforce. About half the teams run the flat fin on the left side and the other half run the curved fin, Marcus said. It partly depends upon the driver's preference for how the car feels in the corners, he said. Either way, NASCAR severely limits the amount of adjustments the teams can make to the wing.

According to NASCAR's Rule 20 - 3.1.3 "B" Rear Wing spec, teams cannot modify the brackets or the wing on their cars or they will be severely penalized. The rule states: "Unless otherwise specified, the rear wing angle may be adjusted within the limits of the NASCAR approved upper and lower mounting brackets. (zero (0) degrees to 16 degrees). The NASCAR approved upper and lower rear wing mounting brackets must not be modified to obtain a rear wing angle of less than zero (0) or more than 16 degrees."

Several teams have learned the hard way that NASCAR is serious about tightly enforcing the rules on the Sprint Cup car -- especially the wing area. Dale Earnhardt Jr.'s team when he drove for Dale Earnhardt Inc. last year and Scott Riggs and Johnny Sauter's teams this year were penalized for messing with their wing brackets and trying to circumvent the rules. The Riggs and Sauter cars were physically confiscated by NASCAR this year. That is a major penalty if they are not returned.

I asked Marcus if the wing would help or hinder cars racing in a pack. He said it should help to stabilize cars that are following other cars in a pack because of the reduced turbulence [dirty air] the wing creates. But that is open for review and debate because the new car is different from the old car so you cannot make valid comparisons without research that, to his knowledge, has not been done.

The designed difference in airflow over the new car is one reason some teams started "yawing" their cars [making them run sideways -- called crabbing -- down the straights] by canting the rear wheels to the right versus having them track straight. By yawing the cars to the right the teams gain additional side and downforce to the body and more downforce to the wing by exposing more car and wing to the onrushing air. This allows the car to be preloaded with both side force and downforce before it transitions into corners and helps keep it from getting loose. It allows the driver to turn the car more easily into and through the corners when the car is yawed.

[+] EnlargeBret Bodine and Kyle Petty
Rusty Jarrett/Getty ImagesWhen NASCAR was still testing and developing the Car of Tomorrow in 2006, alongside the old car, the wing had almosst no vertical fins.
Of course some of the teams got carried away with how much yaw they were using so NASCAR had to step in and set some limits on them. The old "If some is good then more must be better" philosophy. Crabbing got so bad that some teams were having difficulty getting their cars onto the scales during inspection because they could not push them in a straight line.

While this article's primary purpose is to compare the old spoiler to the new wing, you cannot ignore the changes that NASCAR made to the front of the car because they directly effect what happens in the rear. The car has to be aerodynamically balanced if it is to handle well. That means both ends need to be in harmony so the air flow is stable and does not create any surprises for the driver as he moves in and out of traffic on the track.

The new splitter that NASCAR now dictates must be run on all Sprint Cup cars was designed to achieve a specific downforce number. The wing and the splitter could have better and more efficient designs to create more downforce but that is not what NASCAR wanted. Again, they wanted to reduce the amount of downforce while keeping the cars stable but also making them more difficult to drive.

The splitter is more effective than the old air dam, Marcus said, but it could have been much more effective if the horizontal shelf had just been added to the bottom of the old air dam. NASCAR designed the splitter with a flat horizontal shelf that can be run right down on the track surface with the shock bump stops the teams use. But then they added a cavity above it that actually creates some positive lift, which offsets some of the downforce effectiveness of the splitter. That might seem counter productive, and it is under the current setup, but it also gives NASCAR some alternate ways to adjust and fine tune the front end downforce in the future without dramatically changing the current front end profile.

It would appear there is a method to NASCAR's madness with the new Sprint Cup car. Its current configuration is the result of extensive research and study that has created a design that works relatively well today and can be fine tuned as needed now or when needed in the future to keep the sport competitive.

One thing is for sure, the new car is so tightly regulated with templates and laser points, etc. that "creativity" by the teams has almost become a thing of the past.

Bill Borden is a former championship winning crew chief who operated David Pearson's Racing School for many years.