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As applied to racing, the study of airflow and the forces of resistance and pressure that result from the flow of air over, under, and around a moving car.


The “stick” between two touching objects. Adhesion implies a static condition, while traction implies a dynamic (moving) condition.

Air Box:

Housing for the air cleaner that connects the air intake at the base of the windshield to the carburetor.

Air filter:

Paper, gauze, or synthetic fiber element used to prevent dirt particles from entering the engine. Located in the air box.

Air Pressure:

Force exerted by air within a tire, expressed in pounds per square inch (psi).


A belt-driven device mounted on the front of the engine that recharges the battery while the engine is running.


The portion of a racetrack that separates the racing surface from the infield.


Rotating shafts connecting the rear differential gears to the rear wheels.



The sloping of a racetrack, particularly at a curve or corner, from the apron to the outside wall. Degree of banking refers to the height of a track’s slope at its outside edge.

Bell housing:

A cover, shaped like a bell, that surrounds the flywheel and clutch that connects the engine to the transmission.


Slang term for a racecar’s brakes.


(1) “Round of bite” describes the turning or adjusting of a car’s jacking screws found at each wheel. “Weight jacking” distributes the car’s weight at each wheel. (2) Adhesion of a tire to the track surface.

Bleeder valve:

A valve in the wheel used to reduce air pressure in tires.


An overheating of the tread compound resulting in bubbles on the tire surface.

Blown motor:

Major engine failure, for instance, when a connecting rod goes through the engine block. Usually produces a lot of smoke and steam.


The fabricated sheet metal that encloses the chassis.


Pistons travel up and down within each cylinder, or bore, in the engine block.

Brake caliper:

The part of the braking system that, when applied by the driver, clamps the brake disk/rotor to slow or stop the car.



The amount a tire is titled in or out from vertical. Described in degrees, either positive or negative.


A rotating shaft within the engine that opens and closes the intake and exhaust valves in the engine.


A device connected directly to the gas pedal and mounted on top of the intake manifold that controls the air-fuel mixture going to the engine.


The steel structure or frame of the car.


A racetrack straightaway.


A formula or “recipe” of rubber composing a particular tire. Different racks require different tire compounds. “Left-side” tires are considerably softer than “right-side” tires, and it’s against the rules to run left side on the right. There are four basic components: rubber polymers, carbon blacks, oils, and curatives.

Compression Ratio:

Amount that the air-fuel mixture is compressed as the piston reaches the top of the bore. The height the compression, the more horsepower produced.

Contact Patch:

the portion of the tire that makes contact with the racing surface. The size of each tire’s contact patch changes as the car is driven.


The area of the engine block that houses the crankshaft.


The rotating shaft within the engine that delivers the power from the pistons to the flywheel, and from there to the transmission.

Cubic-inch displacement:

The size of the engine measure in cubic inches.

Cut tire:

A slice or puncture of the tread or sidewall due to high speed contact wit debris on the race track or by contact with part of another racecar.

Cylinder head:

Made of aluminum, it is bolted to the top of each side of the engine block. Cylinder heads hold the valves and spark plugs. Passages through the heads make up the intake and exhaust ports.


Deck lid:

Slang term for the trunk lid of a racecar.


Slang term for black, circular, dent-line marks on the side panels of stock cars, usually caused after rubbing against other cars at high speed.


A combination of aerodynamic and centrifugal forces. The more downforce, the more grip you car has. But more downforce also means more drag, which can rob a racecar of speed.


Slang term for the aerodynamic effect that allows two or more cars traveling nose-to-tail to run faster than a single car. When one car follows another closely , the one in front cuts through the air, providing a cleaner path of air, that is, less resistance, for the car in back.


The practice of two or more cars, while racing, to run nose-to-tail, almost touching. The lead car, by displacing the air in front of it, creates a vacuum between its rear end and the nose of the following car, actually pulling the second car along with it.


The resistance a car experiences when passing through air at high speeds. A resisting force exerted on a car parallel to its airstream and opposite in direction to its motion.


A steel tube that connects the transmission of a racecar to the rear end housing.


Shortened term for “dynamometer,” a machine used to measure an engine’s horsepower.


Engine Block:

An iron casting from the manufacturer that envelopes the crankshaft, connecting rods, and pistons.


Slang term used for a series of acute left- and right-hand turns on a road course, one turn immediately following another.



A person who specializes in creating the sheet metal body of a stock car. Most teams employ two or more.


An electrically or mechanically driven device that is used to pull air through the radiator or oil cooler. Heat is transferred from the hot oil or water in the radiator to the moving air.


Slang term for racing a car as fast as possible under the given weather and track conditions.


A heavy metal rotating wheel that is part of the racecar’s clutch system, used to keep elements such as the crank shaft turning steadily.


A type of carburetor.


The metal “skeleton” or structure of a racecar on which the suspension parts and roll cage are mounted. Also referred to as a “chassis.”

Front clip:

Beginning at the firewall, the frontmost section of a racecar. Holds the engine and its associated electrical, lubricating, and cooling apparatus; and the braking, steering, and suspension mechanisms.


Also know as “gasoline.”

Fuel cell:

A holding tank for a racecar’s supply of gasoline. Consists of a metal box that contains a flexible, tear-resistant bladder and foam baffling. A product of aerospace technology, it’s designed to eliminate or minimize fuel spillage.

Fuel pump:

A device that pumps fuel fro the fuel cell through the fuel line into the carburetor.



A thin material, made of paper, metal, silicone, or other synthetic materials, used as a seal between two similar chained metal surfaces such as cylinder heads and the engine block.


An instrument, usually mounted on t eh dashboard, used to monitor engine condition such as fuel pressure, oil pressure, and temperature, water pressure and temperature and RPM (revolutions per minute).


Circular, wheel shaped parts with teeth along the edges. The interlocking of these two mechanisms enables one to turn the other.


How well the tires maintain traction through contact with the racing surface


Slang term for the best route around the racetrack; the most efficient or quickest way around the track for a particular driver. The “high groove” takes a car closer to the outside wall for most of a lap while the “low groove” takes a car closer to the apron than the outside wall. Road racers us the term “line.” Drivers search for a fast groove, and that has been known to change depending on track and weather conditions.



Generally, a racecar’s performance while racing, qualifying, practicing. How a car “handles” is determined by its tires, suspension geometry, aerodynamics, and other factors.


The 18-wheel tractor-trailer rig that teams use to transport two racecars, engines, tools, and support equipment to the racetracks.

Heat cycle:

Each time a tire is raised to operating temperature is a heat cycle.

High heat:

Above normal (260 degrees Fahrenheit) tire temperature.


A measurement of mechanical or engine power. Measured in the amount of power it takes to move 33,000 pounds one foot in a minute.



An electrical system used to ignite the air-fuel mixture in an internal combustion engine.

Intake manifold:

A housing that directs the air-fuel mixture through the port openings in the cylinder heads.

Intermediate track:

Term describing a racetrack one mile or more, but less than two miles, in length.


The time-distance between two cars. Referred to roughly in car lengths, or precisely in seconds.



When air is sent at a high velocity through the carburetor, jets direct the fuel into the airstream. Jets are made slightly larger to make a richer mixture or slightly smaller to make a more lean mixture, depending on track and weather conditions.


Lapped traffic:

Cars that have completed at least one full lap less than the race leader.

Lead lap:

The lap that the race leader is currently on.


See Groove.


Weight at a given tire position on a car due to aerodynamics, vehicle weight and lateral G-forces in a turn.


Also know as “oversteer.” When the rear tires of the car have trouble sticking in the corners. This causes the car to “fishtail” as the rear end swings outward during turns. A minor amount of this effect can be desirable on certain tracks.

Loose Stuff:

Debris such as sand, pebbles, or small pieces of rubber that tend to collect on a track’s apron or near the outside wall during a race.

Lug nuts:

Large nuts applied with a high-pressure air wrench to a wheel during a pit stop to secure the tires in place.



Short for “magnetic particle inspection.” A procedure for checking all ferrous (steel) parts (suspension pieces, connecting rods, cylinder heads, etc.) for cracks and other defect utilizing a solution of metal particles and fluorescent dye and a black light. Surface cracks will appear as read lines.


Excess build-up above the groove on the racetrack. Also known as loose stuff.



A term used when referring to how their car is handling. When a car is neither loose nor pushing (tight).


Oil pump:

This device pumps oil to lubricate all moving engine parts.



A circular element that moves up and own in the cylinder, compressing the air-fuel mixture in the top of the chamber, helping to produce horsepower.

Pole position:

Slang term for the foremost position on the starting grid, awarded to the fastest qualifier.

Post-entry (PE):

A team or driver who submits an entry black for a race after the deadline for submission has passed. A post-entry receives no driver or owner points.


See Tight.



The sheet metal on both sides of the car from the C-post to the rear bumper below the deck lid and above the wheel well.


Rear clip:

The section of a racecar that begins at the base of the rear windshield and extends to the rear bumper. Contains the car’s fuel cell and rear suspension components.


The waving of the green flag following a caution period.

Restrictor plate:

A thin metal plate with four holes that restrict airflow from the carburetor into the engine. Used to rescue horsepower and keep speeds down.

Ride height:

The distance between the car’s frame rails and the ground.


Short for revolutions per minute a measurement of the speed of the engine’s crankshaft.

Roll cage:

The steel tubing inside the racecar’s interior. Designed to protect the driver from impacts or rollovers, the roll cage must meet the strict safety guidelines and are inspected regularly.


Slang term for a way of making chassis adjustments utilizing the racecar’s springs. A wrench is inserted in a jack bolt attached to the springs, and is used to tighten or loosen the amount of play in the spring. This in turn can loosen or tighten up the handling of a racecar.



Slang term for the tuning and adjustments made to a racecar’s suspension before and during a race.

Short Track:

Racetracks that are less than a mile in length.

Silly Season:

Slang for the period that begins during the latter part of the current season, wherein some teams announce driver, crew and /or sponsor changes for the following year.


A track condition where, for a number of reasons, it’s hard for a car’s tires to adhere to the surface or get a good “bite.” A slick racetrack is not necessarily wet or slippery because of oil, water, etc.


A maneuver in which a car following the leader in a suddenly steers around it, breaking the vacuum; this provides an extra burst of speed that allows the second car to take the leads. See Drafting.

Splash ‘n’ Go:

A quick pit stop that involves nothing more than refueling the racecar with the amount of fuel necessary to finish the race.


A blade attached to the rear deck lid of the car. It helps restrict airflow over the rear of the car, providing downforce and traction.


The difference in size between the tires of the left and right sides of a car. Because of a tire’s makeup, slight variations in circumference result. Stagger between right-side and left-side tires may range from less than a half inch to more than an inch. Stagger applies to only bias-ply tires and not radials.


Slang term used for tire traction, as in “the cars sticking to the track.”


Slang term for new tires. The name is derived from the manufacturer’s stickers that are affixed to each new tire’s contact surface,

Stop ‘n’ Go:

A penalty, usually assessed for speeding on pit road or for unsafe driving. The car must be brought onto pit road at the appropriate speed and stopped for one full second in the team’s pit stall before returning to the track.


A racetrack of a mile or more in distance. Road courses are included. Racers refer to three types of oval tracks. Short tracks are under one mile, intermediate tracks are at least a mile but under two miles, and the speedways are two miles and longer.

Sway bar:

Sometimes called an “antiroll bar.” Bar used to resist or counteract the rolling force of the car body through the turns.



A device used to check the body shape and size, to ensure compliance with the rules. The template closely resembles the shape of the factory version of the car.


Also known as “understeer.” A car is said to be tight if the front wheels lose traction before the rear wheels do. A tight racecar doesn’t seem able to steer sharply enough h through the turns. Instead, the front end continues toward a the wall.

Tire compound:

A formula based on rubber polymers, oils, carbon blacks and curatives used to create a tire.


Looking at the car from the front, the amount the tires are turned in or out. If you imagine your feet to be the two front tires of a racecar, standing with your toes together would represent toe-in. Standing with you heels together would represent toe-out.

Track bar:

A lateral bar that keeps the rear tires centered within the body of the car. It connects the frame on one side and the rear axle on the other. Also called the panhard bar.

Trading paint:

Slang term used to describe aggressive driving involving a lot of bumping and rubbing.


a racetrack that has a “hump” or “fifth turn” in addition to the standard four corners. Not to be confused with a trainable shaped speedway, which has only three distinct corners.

200 mph tape:

Also know as “racer’s tape.” Duct tape so string it will hold a banged up racecar together long enough to finish a race.



round of: Adjusting the handling of the car by altering pressure on the rear springs.


Term that refers to the cross weight adjustment of a racecar.

Window net:

A woven mesh that hangs across the driver’s side window, to prevent the driver’s head and limbs from being exposed during an accident.