When the invitation to try out the new formula and sports prototype cars at Virginia International Raceway arrived in my inbox, I was pretty sure I'd have to politely decline. I could hear the boss' response immediately: "So, you just want to spend a day at the track doing laps?"

But this invite stayed on my mind longer than I anticipated. The cars I'd be driving—a Radical SR1 and Ligier Formula 4—both offered something I'd yet to really experience: genuine aerodynamic grip. Maybe there actually was something to be gained by saying yes. The powers that be seemed to agree, and so it was I found myself making the five-and-a-bit-hour drive south from DC in the height of summer, all to find out more about the invisible hand that the racing world calls downforce.

A brief history of aerodynamics

Little attention was paid to the concept of aerodynamics during the first few decades of the automobile. This is not surprising; although foundational work by Bernoulli and Euler dated back to the mid-18th century, any practical applications that existed were focused on taking to the skies. When thought was given to the way a car moves through the air, it was in the aid of top speed. If you could lower the amount of drag on a car, you could make it go faster with less horsepower. This practice was exemplified by the streamlined bodies given to Grand Prix cars from Auto Union and Mercedes-Benz in the 1930s, an effort by German industry to boost the precious ego of its Nazi dictator.

The world war that followed taught us much more about aerodynamics, as clever minds on all sides tasked themselves with building better warplanes. Even so, that knowledge took even more time to trickle down to the more frivolous pursuit of making a faster racing car. Malcolm Sayer at Jaguar was a pioneer here , applying his slide rule to the design of the Jaguar C-Type in order to win Le Mans in 1951 and then again in 1953. Still the application of aerodynamic principles at the time was aimed at cutting drag.

As cars got faster and faster, that other aerodynamic force that we call lift began to assert itself (for lift is proportional to speed). That's great if you're sitting in an airplane and want to fly, but it's more of a problem if you're in a car that's trying to slip the surly bonds of earth. A car's tires only have a finite amount of mechanical grip, which has to be split longitudinally (accelerating and braking) and laterally (turning left or right). If you start to exert lift upon the car, that decreases the loading on the tires. As the load decreases, so does the total amount of mechanical grip. At best, this results in slower acceleration, longer braking distances, and less cornering ability; at worst the driver will simply lose control and crash.

With hindsight, the solution was obvious. If an airfoil moving through the air generates lift, then an inverted airfoil moving through air should generate negative lift. Instead of taking to the sky, a car so equipped should find itself pushed down toward the track, which in turn means more traction. A car that generates downforce can therefore corner faster than one that doesn't. And to make things even better, the faster it goes, the more downforce it generates.

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Jaguar

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In fact, the first known car fitted with downforce-generating wings was built in 1929, a rocket-powered Opel called the RAK2. But for reasons best known to history, it took 35 years for anyone to follow up on the idea. For that, we have to thank an innovative Texan named Jim Hall. Hall was a racer and co-owner of Chaparral Cars, and he started playing with aerodynamic devices on his cars in the mid-1960s in order to improve their stability at speed. At first these were moveable spoilers, but in 1966 the Chaparral 2E showed up with a honking great wing mounted on pylons high above the rear deck, and the racing world was changed forever.

Hall actually gave racing engineers another tool to generate downforce, exploiting what's known as the ground effect. Instead of using an inverted wing, the entire body of the car can generate downforce by means of side skirts and a specially shaped floor (called a venturi) that creates an area of negative pressure underneath it. The most extreme examples of ground effect cars are Hall's 1970 Chaparral 2J and Gordon Murray's 1978 Brabham BT46B, both of which used fans to further reduce the underbody air pressure. In both cases, uproar from their fellow competitors led to the cars being banned (2J) or voluntarily withdrawn (BT46B).

Even without the trick fans, passive ground effect cars were able to generate huge levels of downforce. In Formula 1, Colin Chapman's Lotus team was the first to really crack it, and the 1977 Lotus 78 generated about 40 percent more downforce than any other car on the grid. Ground effect cars quickly became the thing to have, and lap times tumbled as a result.

Generating downforce with ground effects rather than wings had some other benefits. A ground effect design will create fewer kilograms of drag per kg of downforce than a wing. And it isn't as affected by the turbulent wake of air behind another car, which means the racing can be closer. But there was a downside: if something happened to disrupt the seal that separated the underbody airflow—hitting a bump in the track or damaging a side skirt—the effect vanished immediately. There were severe consequences should that happen in a corner. F1 banned the practice in 1983, although the prototypes that raced at Le Mans and in IMSA continued to use ground effects until the early 1990s.

At this point, it would be remiss of me not to note that the advent of downforce in racing hasn't been entirely positive. Cornering speeds have gone up and lap times have gone down, but many believe this has happened at a cost to the actual racing. This year's IndyCar generates significantly less downforce than it did a year ago, which has made the cars harder to drive but added to the spectacle. And the rule makers of Formula 1 are in a constant battle with the teams to limit the amount of downforce those cars generate. But for now, downforce remains a feature in most of the racing world—including a few laps for some journalist at Virginia International Raceway.

Listing image by Jonathan Gitlin