On high-speed oval tracks, IndyCars spend much of a lap fighting air resistance. At speeds above 200 mph, aerodynamic drag becomes one of the largest forces slowing the car, so even a small reduction can change a race. Drafting happens when a trailing car lines up behind a leading car and rides in the disturbed wake.
This lets the trailing car use less power to maintain speed or use the same power to go faster.
Understanding IndyCar Drafting on Ovals
The airflow around the first car does not simply disappear behind it. It is bent around the nose, wheels, cockpit, sidepods, rear wing, and diffuser. Each part leaves swirls and pressure changes.
The largest disturbance often comes from the rear of the car, where the moving air struggles to fill the space left behind. This creates a region with less resistance for a following car, but it is never smooth or uniform.
Small changes in steering angle, car position, or the gap between cars can change the benefit. At oval speeds, a tiny gain in top speed can become a large closing speed over a long straight.
A driver cannot focus only on going faster. The same airflow that helps the car accelerate can make it harder to control in a corner. Wings and the underfloor need fast, predictable air to create downforce.
In disturbed air, the front of the car may lose grip first. The driver then feels that the steering is less responsive and may need to turn the wheel more. If the rear loses more grip, the car can feel loose and unstable.
This is why a car can be very quick while following another car, yet difficult to place accurately near the wall or close to the inside line. Engineers tune wing angles, suspension settings, and weight distribution to give the driver a car that remains usable in these conditions.
The best passing move depends on timing. A driver often stays tucked in behind long enough to build extra speed, then pulls out shortly before the next corner or the finish line. Moving out too early exposes the car to full air resistance before the speed advantage is large enough.
Moving out too late may leave no room to complete the pass safely. Once two cars run side by side, their airflow changes again.
The car on the outside may have a longer path through the turn, while the car on the inside may have less space and a tighter corner radius. A third car behind them can gain an even stronger run because it benefits from the disturbed air of both cars.
Drafting affects race strategy as much as single passes. Running in a group can save fuel because the engine may need less throttle to hold a competitive speed. That can allow a later pit stop or a shorter refuelling stop.
It can also raise risks. Drivers must judge closing speed, especially when approaching a slower pack or entering a turn. At more than 200 mph, a gap that looks safe can vanish in a moment.
When studying this topic, pay attention to relative speed rather than just each car's speed. Notice how track banking, corner radius, tire grip, and airflow all decide whether a drafting run becomes a clean pass or an unstable situation.
Key Facts
- Aerodynamic drag increases with the square of speed: Fd = 1/2 rho Cd A v^2.
- The power needed to overcome drag increases roughly with the cube of speed: P = Fd v.
- A wake is a region of slower, lower-pressure, turbulent air behind a moving car.
- A trailing IndyCar in the wake experiences reduced drag because the air speed relative to the car is lower and pressure drag is reduced.
- A slingshot pass happens when the trailing car gains speed in the draft, then moves into clean air to pass.
- Drafting can reduce drag, but turbulent air can reduce downforce and make steering less stable.
Vocabulary
- Drafting
- Drafting is driving closely behind another vehicle to reduce aerodynamic drag by using its wake.
- Aerodynamic drag
- Aerodynamic drag is the force of air resistance that acts opposite to a car's motion.
- Wake
- A wake is the disturbed, slower, turbulent region of air left behind a moving object.
- Downforce
- Downforce is the aerodynamic force pushing a race car downward to increase tire grip.
- Slingshot pass
- A slingshot pass is a move where a trailing car builds speed in the draft and then pulls out to pass the leader.
Common Mistakes to Avoid
- Thinking drafting removes all air resistance is wrong because the trailing car still moves through air and still has drag, just less than in clean air.
- Assuming the trailing car can stay safely inches from the leader is wrong because reaction time, turbulence, and sudden speed changes make very close following dangerous.
- Confusing low drag with high downforce is wrong because the wake can reduce drag but also disturb airflow over the wings and reduce grip.
- Using drag as a linear force at racing speeds is wrong because aerodynamic drag depends on v^2, so small speed increases cause much larger drag increases.
Practice Questions
- 1 An IndyCar has a drag force of 4200 N in clean air at 90 m/s. If drafting reduces drag by 18 percent, what drag force does the trailing car feel?
- 2 A car needs 378 kW to overcome drag at a certain speed in clean air. If drafting reduces the drag force by 15 percent at the same speed, what power is needed to overcome drag while drafting?
- 3 A trailing driver gains speed in the draft before pulling out to pass. Explain why the car may speed up in the wake but become harder to control when it moves through turbulent air near the leader.