Why Cars Need Downforce

We’ve all seen race cars and how they utilize aero kits, canards, splitters, diffusers and wings to help improve their performance. But why go through all the trouble to seek that competitive edge? What are the dynamics going on that makes race teams spend so much time and resources on improving their cars aerodynamics? To understand the dynamics involved with such components, it is important to know some principals of aerodynamics.

The Effects of Lift and Downforce
Depending on its shape, an object traveling through air will always be lifting upward or downward. If it’s lifting upward, the effect is simply known as lift. If it’s downward, the effect is known as downforce. Most cars lift as they travel through air because of their shape. The reason why is because of an aerodynamic principal discovered by Swiss scientist Daniel Bernoulli. The Bernoulli Effect simply states the higher the speed of air molecules traveling around an object, the lower the air pressure becomes around that object. In contrast, the lower the speed of air molecules traveling around an object, the higher the air pressure becomes.

As a car travels forward it is bombarded with air molecules. Air needs places to escape once they have approached the front of the car. They can either flow over, around and under the car. You would think that since there is more space above the car, air pressure should be higher on the top surface, but that is not the case. A car has lower pressure on the top and higher pressure below because of the Bernoulli Effect. Since the speed of air molecules travels faster over the top of the car, the density of air molecules becomes lower making low pressure above the car. Alternately, because air travels faster over the top and slower below the car, more air molecules are squeezed underneath a car making the pressure higher. These forces are what cause cars to lift up as they gain speed.

Problems with Lift and the Importance of Downforce on the Race Track
If a race car is constantly lifting, it does not have the traction and control it needs to go fast and those are some of the key components to faster lap times. Cars need controllability and traction to retain higher speeds through turns. If a car cannot retain higher speeds through turns, then time ultimately is lost.

One example of how much lift can be generated on a car is the lift on a stock 2000 Volkswagen Beetle. A stock Beetle can produce 742 lbs of lift at 124 mph! Since a Beetle weights roughly 2700 lbs, nearly 25% of a Beetle’s weight is actually lifting at that speed. Imagine building a high powered Beetle race car. You think with 25% less ground traction at 124 mph to the ground will be beneficial to a faster time on a straight away?

To combat lifting, aerodynamic components are utilized to produce downforce. Components such as aerodynamic kits, canards, splitters, diffusers and wings are performance additions race car teams have utilized to create downforce for their race cars. APR has developed their product line to not only give street cars a race car appearance, but to also give street cars a functional performance upgrade that can help on the race track. That’s why many road racers, drifters and drag racers have trusted APR products on their cars when time to battle on the track has come.