Indianapolis 500 technical terms, and what they mean to fans

Do you like watching the Indianapolis 500 but can't relate to what the gearheads and analysts are saying? We're here to help.

While strategists, team bosses, drivers and television announcers are speaking English, it's easy to feel like you're hearing a foreign language. What is a "tow," or "marbles," or "boost?"

With the help of the IndyCar Series media guide, here are some of the phrases you'll likely hear when the cars are on track.

Indy 500 aerodynamics terms: chassis, downforce, tow, push, loose

• Aerodynamics: You will hear analysts discuss a car's "aero package." In racing, that means the interaction between air and the resistance and pressures created as a car cuts through air on the track.
• Chassis or "tub": The central body of the car, including the driver’s compartment. Dallara produces chassis for Indy cars.
• Dirty air: Unstable airflow resulting from leading cars that can affect downforce, grip and cornering for a trailing car. On the IMS oval, a single car splitting the air on a long straightaway can help create a "tow" (see below), but multiple leading cars can create more difficult conditions for a trailing car. Also, the abrupt change of going into a corner can create dirty air for trailing cars.
• Downforce: Wings that keep the car grounded?! Creation of force through aerodynamics, which keeps the car stuck to the track. High-speed movement of air underneath the car creates a vacuum, while the wings on the car force it to stay on the ground, acting in a manner opposite to the wings of an airplane.
• Drafting, or "tow," no-tow laps: As the car moves around the track, it splits the air, some going over the car and some beneath. This lack of air behind the car creates a vacuum, can pursuing cars can use it to be pulled or “towed.” During the first week of practice, there will be a differentiation between overall fastest laps, which would likely be aided by a tow, and "no-tow" laps, when a car is running without the aid of a leading car. Qualifying laps are "no-tow" laps.

What classifies a tow vs. no-tow speeds?

These #Indy500 drivers have you covered ⬇️ pic.twitter.com/PtxiUplBwR— NTT INDYCAR SERIES (@IndyCar) May 14, 2026

• Loose or "oversteer": Term used to describe that rear of the car is unstable because of a lack of rear-tire grip. That can be caused by too much front downforce or not enough rear downforce.
• Push or "understeer": Term for a car that does not want to turn in the corners because of a lack of tire grip. This can be caused by a lack of downforce on the front of the car or too much downforce on the rear of the car.
• Wicker bill: A long, narrow, removable spoiler made of steel, aluminum or carbon fiber on the trailing edge of the front and rear wings that varies in height, creating downforce. Teams will use different sized wicker bills to create more or less downforce.

Indy 500 tire terms: Blister, grip, line, marbles, sticker

• Blister: Kind of like those nuisances on your toes or feet, these bubbles on the surface of a tire are created by excessive heat. This can affect the car's handling.
• Grip: How well the tires maintain traction through contact with the racing surface.
• Groove or line: Term for the fastest or most efficient way around the racetrack. Most drivers will use the same groove around the racetrack and that portion of the track will consequently appear darker in color than the rest of the track because of the buildup of tire rubber.
• Marbles: As tires degrade, tiny bits resembling marbles break off. That creates excess rubber buildup above the groove on the track. If cars drift into the marbles, the chances of a spin or crash increase.
• Sticker tires: New tires. Tire manufacturer Firestone places a sticker on each new tire.

Indy 500 safety terms: aeroscreen

• Aeroscreen: Introduced in 2020, this ballistic, canopy-like windshield is anchored by a titanium framework than encompasses the cockpit and is mandatory for all cars.

Indy 500 engine terms: Boost, fuel, turbo

• Boost: Manifold intake pressure above ambient atmospheric pressure. Cars are allowed extra boost on Fast Friday and in qualifying.
• Ethanol or fuel: A renewable fuel made from various plant materials collectively known as “biomass.” The IndyCar Series uses Shell 100% renewable race fuel, in which second-generation ethanol made from sugarcane waste is blended with other biofuels to create a renewable product.
• Turbocharger: Routes engine exhaust gases to turn a turbine, which powers a compressor that forces a greater volume of air into the engine’s intake system, thus increasing horsepower and fuel efficiency. The turbocharger debuted at Indy in 1952 and eventually replaced carburetors by the mid 1960s.

Indy 500 cockpit terms: Paddle shift, weight jacker

• Paddle shift system: Shifting gears at the Indianapolis 500 isn't at all like using a manual shift passenger car. A pneumatic gearshift paddle system allows the driver to keep bothhands on the steering wheel during shifting by using paddles located on the back of the steering wheel to shift up and down. The paddle shift system has its own control unit that is in sync with the engine, so it knows what gear the car is in, engine RPMs and the speed of the car.
• Weight jacker: A hydraulic cylinder the driver controls to adjust car handling. The cylinder is mounted on top of a rear shock spring and compresses or extends, transferring the car’s weight distribution from one side of the car to the other, adjusting the car’s handling to the driver’s liking.

Indy 500 track terms: Weeper

• Weeper: If there's excessive rain at the Speedway, even after the track has dried and cars have been on the track, damp spots where water has seeped through asphalt can occur. Those are called "weepers" and often prompt a caution.

Zion Brown is IndyStar's motorsports reporter. Follow him at @z10nbr0wn. Get IndyStar's motor sports coverage sent directly to your inbox with our Motor Sports newsletter.

This article originally appeared on Indianapolis Star: What Indy 500 fans should know about technical terms