Episode 4: The Shape of Speed
Introduction
Here is a fact that does not sound true, but is.
A modern Indianapolis 500 race car, traveling at 230 miles per hour around the Indianapolis Motor Speedway, is being pushed into the track by aerodynamic forces stronger than the weight of the car itself.
If you could keep enough air flowing over the wings of an Indy car, the car could theoretically drive upside down across the ceiling of a tunnel. The air would hold it there.
This is not a trick. It is not exaggeration. It is the entire reason a modern Indy car exists. Without that downward force, the car could not corner at 220 miles per hour. It could not even stay on the ground.
Today we are going to talk about something most people cannot see, most people cannot feel, and most people never think about. We are going to talk about air. And specifically, we are going to talk about how a team of engineers in Italy, working with a team of engineers in Speedway, Indiana, figured out how to shape the air that flows over and under a race car so precisely that the car, weighing about as much as a small SUV, ends up pinned to the track by 4,000 pounds of force.
We are also going to talk about the math behind it. The same physics equation that holds airplanes up holds Indy cars down. And it has one feature that makes it the most important equation in motorsports.
All 33 Cars Are the Same Car
Before we get to the physics, you need to know one fact about the Indianapolis 500 that surprises almost everyone the first time they hear it.
All 33 cars in the field have the same chassis.
Not similar chassis. Not chassis built by 33 different teams. The same chassis. They are all built by the same company, in the same factory, on the same assembly line, to the same exact specifications.
The chassis is called the Dallara IR-18. It was introduced in 2018 and it has been the chassis of every Indy car since then (Indianapolis Motor Speedway, 2026). The "Dallara" part comes from the name of the Italian company that designs and builds it. The "IR" stands for IndyRacing. The "18" stands for 2018.
Here is the story of how an Italian company ended up building every Indianapolis 500 car in a factory in Speedway, Indiana, less than a half mile from the IMS main gate.
Dallara was founded in 1972 by a man named Giampaolo Dallara. He had previously worked as an engineer at three of the most legendary Italian car companies in history: Lamborghini, Ferrari, and Maserati. He left those companies to start his own, focused on designing and building the most competitive race cars in the world (Life In Indy, 2024).
For about twenty years, Dallara worked mostly with European racing series. Then in 1996, the Indy Racing League was founded, and the new league needed chassis manufacturers willing to compete on American oval tracks. Dallara took the leap. They had never built a car for oval racing before. They sent four employees from Italy to live in Indianapolis. By 1997 they were on the grid (Indianapolis Motor Speedway, 2023).
By 1998, an Italian-built Dallara chassis won the Indianapolis 500.
For the next decade, Dallara built chassis for many of the top IndyCar teams. Then in 2010, IndyCar made a major decision. Instead of allowing teams to design their own chassis, the series would use one standardized chassis for everyone. This is called a spec chassis rule. The idea is that when every team is racing the same car, the differences come down to driver skill, team strategy, and small setup decisions, not who has the biggest engineering budget.
Dallara won the contract to be that single chassis supplier. The contract started in 2012 (Wikipedia, Dallara DW12, 2026).
To service American teams, Dallara built a 114,000 square foot factory in Speedway, Indiana, one-third of a mile from the front gate of the Indianapolis Motor Speedway (Indianapolis Motor Speedway, 2023). At the start they had nine or ten employees. Today they have over 50. The Speedway facility builds and assembles the suspension, body panels, carbon fiber components, and many other parts that go into every Indy car on the grid.
Target: Dallara USA engineer (Eric Snyder, assembly supervisor and motorsports technical support director, or current chassis engineer). Topic: What is it actually like to build the chassis that all 33 Indy 500 cars are built around? Length: ~30 seconds. Fallback narration if clip is not available: "Dallara USA employs more than 50 people in their Speedway, Indiana factory. They build the suspension, body panels, engine covers, and carbon fiber parts that go onto every Indy car on the grid. They also operate one of only three Dallara driving simulators in the world; the other two are in Italy."
The chassis itself is a monocoque made primarily of carbon fiber composite. It costs roughly $349,000 per car. Each Indy 500 team owns several copies of the same chassis, because they need spares for practice, qualifying, and the race itself (Wikipedia, Dallara DW12, 2026).
So if all 33 cars are built on the same chassis, what makes them different? Three things:
- Engine : either Honda or Chevrolet supplies the 2.2 liter twin-turbocharged V6
- Setup : each team adjusts the suspension, the angle of the wings, and the tire pressures for the specific track
- Aerodynamics package : there are two options, one for high-speed superspeedways like IMS, and one for road and street courses
That third one, the aerodynamics, is what we are going to spend the rest of this episode on. Because aerodynamics is where the laws of physics meet the limits of human engineering.
Newton's Third Law at 230 MPH
OK, time for some physics. Stick with me.
You have probably heard of Newton's Laws of Motion. There are three of them, and the third one is the one we need today.
Newton's Third Law: For every action, there is an equal and opposite reaction.
That is the entire law. Five short clauses. And it is the reason a Boeing 747 weighing 800,000 pounds can fly through the air, and it is also the reason an Indy car weighing 1,650 pounds gets pinned to the track at 230 miles per hour.
Here is how it works on an airplane. An airplane wing is curved on top and flatter on the bottom. As the wing moves forward, the curved top surface forces the air above the wing to travel a longer path than the air below the wing. The air on top has to speed up to keep up. That speeding up creates lower pressure on top of the wing.
So the wing has higher pressure below and lower pressure above. The pressure difference pushes the wing up. The plane flies.
That is called lift. Lift is the force that holds airplanes in the sky.
Now imagine taking that exact wing, the one designed to push the airplane UP, and flipping it upside down. Now the curved surface is on the bottom and the flat surface is on top. The same air-flow physics happens, but in reverse. The air goes faster under the wing, creating low pressure under it. High pressure above pushes the wing down.
That is downforce. And that is what every wing on every Indianapolis 500 car is doing. The wings are upside-down airplane wings.
Now, Newton's third law tells you something more. If the wing is being pushed DOWN by 1,000 pounds of force, then the wing is pushing 1,000 pounds of air UP. The action of the air pushing the car down has an equal and opposite reaction: the car pushes the air up. Same magnitude, opposite direction.
So when an Indy car is going 230 miles per hour around IMS, and the wings are generating 3,000 pounds of downforce, the car is also throwing 3,000 pounds of air upward into the sky behind it.
If you have ever stood next to a road when a semi-truck blasts past you and felt a wall of air shove at you, what you are feeling is the same effect. The truck displaced a volume of air. The air had to go somewhere. It went into you.
For an Indy car, that displaced air is the "dirty air" the broadcasters talk about. It is the turbulent wake of air behind a car at speed. It is also why following another car closely is so hard at the Indy 500. The dirty air behind a lead car disrupts the airflow over the wings of the trailing car, reducing its downforce, making it slide instead of stick.
The drivers who win at IMS are the drivers who understand how to manage that dirty air.
Now here is what is amazing. A modern Indy car generates so much downforce that, at top speed, it weighs more aerodynamically than it weighs mechanically. Without the wings, the car has a mass of about 1,650 pounds including the driver. With the wings doing their job at 230 mph, the car is being pressed into the track with several thousand additional pounds of force (RACER, 2025).
This is why the car can corner at 220 mph and not slide off the track. The tires have enough grip because the wings are forcing the car onto the tires.
This is also why, if you took the wings off an Indy car and tried to drive it at 230 mph, the car would lose grip, lift slightly off the ground, and crash spectacularly. We know this is true because it has happened.
The Three Surfaces
So if downforce is generated by wings, how many wings does an Indy car have?
Three primary surfaces. Three ways the car shapes the air to push itself down.
Surface One: The Front Wing.
You see the front wing every time you look at the nose of an Indy car. It is the lowest, narrowest part of the car, just inches above the ground. It has multiple elements: typically a main plane and several flaps. These elements work together to create a high-pressure pocket above the wing and a low-pressure pocket below.
The front wing creates roughly 30% of the car's total downforce. But the front wing has another job that is just as important. It steers the air. Whatever air the front wing does not push down, it has to direct cleanly around the front tires and along the sides of the car. If the air comes off the front wing turbulent, every other aerodynamic surface on the car works worse.
A great front wing is the difference between a car that grips and a car that pushes the front tires sideways through a corner.
Surface Two: The Rear Wing.
Look at any Indy car from behind. That tall wing sticking up at the back, with the multiple elements stacked above each other, is the rear wing. It is the most visible aerodynamic component on the car.
The rear wing creates roughly 40% of the car's total downforce. It works just like the front wing: upside-down airplane wing geometry, high pressure above, low pressure below. But because the rear wing is bigger and higher, it works on cleaner, faster-moving air that has not been disturbed by the front of the car.
The rear wing is also adjustable. Teams can change the angle of the wing flaps between sessions. A steeper angle means more downforce but more drag. A flatter angle means less downforce but more straight-line speed. We will get to this trade-off in just a minute.
Surface Three: The Floor.
This is the hidden one. Most fans never think about it. But the floor of an Indy car (the entire underside, plus tunnels carved into specific shapes) generates the remaining 30% or so of the car's total downforce. And it does so with almost no drag penalty.
This is called ground effect. Here is how it works. The bottom of the car is shaped like an upside-down half-pipe in places, with channels that get narrower in some sections and wider in others. As air rushes under the car, it accelerates through the narrow sections and slows through the wider sections. Where the air moves faster, the pressure drops. Lower pressure under the car means the higher-pressure air above pushes the car down.
Ground effect is essentially free downforce. It costs almost nothing in drag. It is one of the most important innovations in race car design from the last 50 years.
Target: Current Indy car aerodynamicist (could be a Dallara designer, an IndyCar series engineer, or a team aerodynamicist). Topic: How do you think about balancing the front wing, rear wing, and floor when designing or setting up a car? Length: ~30 seconds. Fallback narration if clip is not available: "Indy car aerodynamicists describe the three surfaces as a balance problem. If you optimize the rear wing without considering the front, the car becomes 'understeery,' meaning the front tires lose grip in corners. If you optimize the front without the rear, the car becomes 'oversteery,' which is even more dangerous at 220 mph. The art of the job is keeping all three surfaces in productive conversation with each other."
Three surfaces. Front wing for 30% of the downforce. Rear wing for 40%. Floor for 30%. Each one designed by the engineers at Dallara USA in Speedway, Indiana. Each one shaped to push the car onto the track so it can do what it does.
The Math That Scales Everything
Now we are going to look at one specific equation. This is the equation that governs every wing on every Indianapolis 500 car. It is also the equation that governs every wing on every airplane. It is one of the most important equations in fluid dynamics. And it has one feature that, once you see it, you cannot unsee.
Here is the equation:
F = ½ × ρ × v² × C × A
where:
- F is the aerodynamic force (in newtons)
- ρ (rho) is the density of the air (about 1.225 kg/m³ at sea level)
- v is the velocity of the car (in meters per second)
- C is the coefficient of lift or downforce (a dimensionless number that depends on the shape of the wing)
- A is the reference area of the wing (in square meters)
Let me read it in plain English. The aerodynamic force on a wing equals: one-half, times the density of the air, times the velocity squared, times the wing's coefficient, times the wing's area.
Let me unpack that.
ρ, the density of air. Air at sea level has a density of about 1.225 kg/m³. That is roughly one one-thousandth of the density of water. Higher altitude (thinner air) means less density, less force. This is why airplanes have to fly faster at high altitude to generate the same lift, and it is also why Indy cars at the high-altitude Pikes Peak hill climb have slightly less downforce than at sea-level IMS.
v, velocity. This is how fast the car is moving. In meters per second, because that is the standard physics unit.
C, the coefficient. This is a number that depends entirely on the SHAPE of the wing. A flat board has a C close to zero. A perfectly shaped wing might have a C of 2 or 3 or higher. The engineers at Dallara spend years optimizing this number.
A, the area. The bigger the wing, the more force it generates. But bigger wings also create more drag, so this is a trade-off.
And finally, the one with the special role: v², the velocity SQUARED.
That little exponent of 2 is the most important thing in motorsports.
Because v² means that as the speed of the car increases, the force on the wings does not increase proportionally. It increases as the square of the speed.
Let me show you what that means. Imagine an Indy car at 100 miles per hour. With realistic numbers for a road-course aerodynamic setup, the wings generate about 1,240 pounds of downforce.
Now imagine doubling the speed to 200 miles per hour. You might guess that doubling the speed doubles the downforce, so 2,480 pounds.
Wrong. Doubling the speed multiplies the downforce by 2², which is 4. At 200 mph, the same car generates about 4,950 pounds of downforce. Four times as much.
Now triple the speed from 100 mph to 300 mph. You might guess the downforce triples. Wrong. It increases by 3², which is 9. Nine times as much.
This v² scaling is THE central fact about racing. It is why slow corners and fast corners are completely different problems. In a slow corner at 60 miles per hour, the wings are barely doing anything. The car relies almost entirely on tire grip. In a fast corner at 200 miles per hour, the wings are generating more force than the car weighs. The car is being held to the track by air pressure.
This is also why high-speed crashes at IMS are so violent. The car is locked to the track by thousands of pounds of force, and if anything disrupts that force suddenly, the car can become airborne almost instantly.
The v² scaling shows up everywhere in racing physics. It is also why kinetic energy (the energy of motion) scales with v². A car going 100 mph has four times the kinetic energy of a car going 50 mph. A car going 200 mph has 16 times the kinetic energy of a car going 50 mph. This is why high-speed crashes are exponentially more dangerous than low-speed crashes.
Memorize one thing from this episode: velocity squared. That little exponent of 2 governs almost everything about racing.
Drag vs. Downforce
OK, if more downforce is better, why do engineers ever choose to use less of it?
Because of a thing called drag.
Every wing that generates downforce also creates drag. Drag is the force that pushes back against a car's forward motion. The more aggressive your wings are (the steeper the angle, the more flap elements, the bigger the area), the more downforce you generate. But the more drag you also create.
So you have a trade-off. More downforce means better cornering grip. But more drag means slower straight-line speed.
This is why Indy cars use two completely different aerodynamic packages depending on the track.
For a road course or a street course (lots of corners, shorter straights), teams run the high-downforce package. Bigger front and rear wings. Steeper angles. More flap elements. The car corners better but is slower on straights. The trade-off is worth it because there are so many corners.
For a superspeedway like Indianapolis (long straights, only four corners, and those corners are taken at speeds where drag matters more than wing-generated downforce), teams run the low-downforce package. Smaller, flatter wings. Less drag. The car has less aerodynamic grip in corners, but it goes much faster down the straights, and the corners at IMS are taken at speeds where the floor's ground effect provides most of what is needed (iRacing, 2026).
To put this in real numbers: an Indy car in road-course trim might generate 6,000 pounds of downforce at top speed. The same chassis in IMS oval trim generates closer to 3,000 to 3,500 pounds. About half. And the top speed at IMS is 25-30 mph higher than the top speed on a road course because of the reduced drag (RACER, 2025).
This trade-off is the heart of race car engineering. It is also a great example of a broader principle in engineering: you do not optimize for one thing; you optimize for the right balance among many things. A car that corners perfectly but is too slow on straights will lose. A car that screams down straights but cannot corner will lose. A car that does both okay will win.
A young engineer learns this trade-off in school and spends the rest of their career getting better at finding the right balance for the specific situation they are facing. The same principle applies to almost every engineering field. In aerospace, in civil engineering, in mechanical design, in software, the same fundamental truth holds: there is almost always a trade-off, and the engineer's job is to find the right one.
Wind Tunnels and Computer Simulations
So how do you actually design these aerodynamic surfaces? How does a Dallara engineer in 2026 figure out what shape the front wing should be?
Two ways.
Way One: The wind tunnel.
A wind tunnel is exactly what it sounds like. You build a scale model of the car (or sometimes a full-size version), put it inside a giant enclosed chamber, and blast air at it with industrial fans. Sensors on the model measure the forces. Smoke tracers show where the air is flowing. Engineers iterate the design, build another model, run the tunnel again.
Wind tunnels are real. They are accurate. And they are expensive. Renting wind tunnel time can run thousands of dollars per hour. Building your own is tens of millions of dollars in capital costs.
Way Two: Computational Fluid Dynamics, or CFD.
CFD is wind tunnel testing, but inside a computer.
Engineers build a 3D model of the car. Then they break the space around the car into millions of tiny cells. The computer calculates what the air does in each cell, then how each cell interacts with its neighbors, then iterates the whole thing thousands of times until the air pattern stabilizes.
Modern CFD requires enormous amounts of computing power. A single simulation might take a supercomputer hours or days to run. But once it runs, it tells the engineer exactly how much force is on the car, exactly where the pressure is high and low, and exactly where the air is moving turbulently versus smoothly.
CFD has revolutionized race car design over the last twenty years. Teams that once needed millions of dollars in wind tunnel time can now do much of the same work with a fraction of the budget. Smaller teams can compete with bigger ones. Innovations come faster.
Target: A Purdue Motorsports Engineering alumna or alumnus working on a 2026 Indy 500 team (Angela Ashmore, Lizzie Todd, Matt Kuebel, or Nathan O'Rourke are all named alumni in this pipeline). Topic: What does your day look like? How did Purdue prepare you for this work? Length: ~30 seconds. Fallback narration if clip is not available: "Purdue University in Indianapolis offers the only ABET-accredited Motorsports Engineering bachelor's degree in the United States. Every American-based 2025 Indy 500 team had at least one Purdue Motorsports Engineering alum on staff. Graduates work in chassis design, aerodynamics, race strategy, and CFD. The pipeline from Indiana high school, to Purdue Motorsports Engineering, to the Indy 500 paddock is real, and it is open to any Indiana student who wants to try it."
The combination of wind tunnels and CFD is how Dallara designs every wing, every floor, every body panel on the IR-18 chassis. It is also how individual Indy 500 teams optimize their setups for race weekend. Hours of CFD simulation feed into seconds of decision-making on the timing stand.
Wrap-up
Here is what I want you to take from Episode 4.
Aerodynamics is one of the most fundamentally important fields of engineering in the world, and it touches everything. Race cars, sure. But also: airplanes, helicopters, drones, wind turbines, building design (yes, the wind load on skyscrapers), and even the design of pharmaceutical inhalers and the way you throw a baseball.
If you find any of this interesting, the career path is real and it is accessible.
The most direct route, if you live in Indiana, is Purdue Motorsports Engineering in Indianapolis. The only ABET-accredited Motorsports Engineering bachelor's degree in the United States. It is a real four-year program, full of mechanical engineering, computer-aided design, fluid dynamics, materials science, and hands-on car work. Graduates go into Indy 500 teams, NASCAR teams, Formula One, aerospace, the automotive industry, and more.
But you do not have to go to Purdue. Aerospace engineering, mechanical engineering, and physics programs at Indiana University, Indiana State, Ball State, and many other Indiana schools all offer relevant degrees. The fundamentals of fluid dynamics are taught everywhere.
And if you want to start before college, build something. A model rocket. A balsa-wood airplane. A windmill in your back yard. A water bottle rocket. A paper airplane that you tune by changing wing angle. All of these are real aerodynamics experiments. You will learn more about lift, drag, and downforce by building a thing and watching what happens than you will from any textbook chapter.
The Dallara engineers in Speedway, Indiana, who are designing the next chassis for IndyCar (the IR-28, coming in 2028), all started somewhere. Most of them started with a curiosity about how things move through air. Some of them started in Italy. Some of them started in Indianapolis. The path is not the point. The curiosity is.
This week, find one moving thing. A frisbee. A leaf falling. A bird's wing. A windsock. Watch how it moves through air. Ask why. That is how every aerospace engineer in human history got started.
Sources
Coach Dave Academy. (2025). iRacing Dallara IR18 IndyCar guide & setups. https://coachdaveacademy.com/tutorials/iracing-guide-we-look-at-the-dallara-ir18-indycar/
Dallara Experience Hub. (2025). About the Dallara Experience Hub. https://dallaraexperiencehub.com/
iRacing. (2026). Dallara IR18 INDYCAR. https://www.iracing.com/cars/dallara-ir18/
Indianapolis Motor Speedway. (2023). 1998 Indianapolis 500 win paved path for Dallara dominance. https://www.indycar.com/news/2023/05/05-24-dallara-25thanniversary
Indianapolis Motor Speedway. (2026). Inside INDYCAR Racing: What makes the NTT INDYCAR SERIES race car unique? https://www.indycar.com/Fan-Info/INDYCAR-101/Cars
Life In Indy. (2024). Why choose Indy: How Dallara landed in Speedway, Indiana. https://lifeinindy.com/industry-news/dallara-landed-in-speedway/
NGSS Lead States. (2013). Next Generation Science Standards: For states, by states. The National Academies Press.
RACER. (2025). IndyCar 2028: The chassis. https://racer.com/2025/12/11/indycar-2028-the-chassis
Visit Indy. (2025). Dallara Experience Hub. https://www.visitindy.com/listing/dallara-indycar-factory/224646/
Wikipedia. (2026). Dallara DW12. https://en.wikipedia.org/wiki/Dallara_DW12