Racing Glossary (Racing 101)

A component of suspension, these metal or carbon fiber rods connect the tires and wheels to the chassis.  They are usually shaped like an "A", with the point of the A connected to the wheel and the bottom two points of the A connected to the chassis.  There are usually two A-arms at each wheel, one top and bottom. Also called wishbones

The science of managing airflow plays a major role in racecar design and tuning because modern day open wheeled cars are highly sophisticated aerodynamic devices. Areas of high and low pressure are carefully managed to maximize downforce (to give a car grip) while minimizing drag (to maximize speed). You can see the wings on the nose and the large wing at the rear of the car. Underneath, two large grooves (like funnels cut in half) suck the car down on the track by creating a partial vacuum under the car. This is generally referred to as "ground effects." Wind tunnels play a key role in modern day open wheeled cars design and evolution.

Mechanics can adjust a car's handling by raising or lowering air pressure in the tires. Flex in the sidewall of a tire acts like another spring in the suspension. Increasing the air pressure makes the overall spring rate higher, while lowering the pressure will make it softer. This adjustment can be made much more quickly and easily than changing a spring on a shock.

A mechanical linkage, one each for the front and rear suspensions, that helps transfer more weight to the inside tires in the corners and helps keep all four tires gripping the track. The driver adjusts the anti-roll bars with levers in the cockpit. Also called a sway bar.

The geometric inside center point of a corner. In racing, a driver will often use a "late apex," turning into the corner a little later than normal in order to straighten out the last part of the corner. This allows the driver to accelerate earlier and harder, gaining maximum speed down the next straight.

A car running near the back of the field.

The fireproof hood drivers wear under their helmets to avoid burns to the face and neck.

On oval tracks, the corners are often tilted inward to provide faster speeds. On some road courses, certain turns may actually be banked outward, a very difficult type of corner known as "off-camber."

This flag is waved by the starter to signal a driver that he or she must immediately report to the pits for consultation related to a dangerous mechanical condition or a driving infraction. Failure to heed the flag can result in exclusion from the final results of the event. This flag may also be displayed in a "furled" (rolled-up) manner as a warning. Corner workers may also display a black flag if the session has been halted by the display of a red flag by the starter.

This flag is displayed by corner workers around the track to signal to a driver that a faster car is either approaching (steady flag) or attempting a pass (waved flag). The driver being flagged has no obligation to do anything other than be alert, maintain the racing line and avoid intentionally obstructing the faster car.

The exterior of the car. The bodywork is generally made from carbon fiber. The panels lift off in sections so mechanics can get to mechanical components easily and quickly. Bodywork is carefully sculpted to maximize aerodynamic efficiency.

In most cars, including street cars, pressing on the brake pedal applies a little more force to the front brakes than the rear. This is designed to take advantage of the fact that under braking, weight transfers to the front of the car. With lots of weight on the front tires, the brakes can be applied very hard without completely stopping the wheels from rotating ("locking the wheels"). At the same time, the rear of the car tends to get lighter, so the rear brakes must be engaged less than the fronts to avoid locking the rear wheels and possibly losing control. In a racecar, brake bias is adjustable by the driver to compensate for changing conditions, such as on a wet track where there is less weight transfer to the front of the car under braking, or to adjust for a changing center of gravity as fuel is burned off.

Brakes transform motion into heat. The heat in the  rotors of a car can reach 5,000 degrees F. When the fluid in the brake system exceeds its boiling point due to hard use, bubbles can form in the brake lines and calipers. Since these bubbles can be squeezed smaller by pressure from the brake pedal, the pedal tends to "go soft" and may even go to the floorboard without the brakes working properly.

In shock absorbers, a bump adjustment is a change to the dampening of the shock on the compression stroke. As a car passes over a bump on the track, each wheel assembly rises up to pass over it. Without compression dampening, the momentum of the wheel assembly would cause it to continue to rise after the bump until the spring finally overcomes the inertia and pushes the wheel back down. Since a tire can't do any work while in the air, bump dampening stops the upward momentum and allows the tire to stay in constant contact with the pavement. Bump adjustments also affect how the weight of the car shifts around during braking, acceleration and cornering, known as "weight transfer."

Refers to changes in wheel alignment (toe, camber and caster) as the wheel moves through the suspension range. Wheel alignment is set with the car stationary, so bump steer affects must be properly considered to ensure that suspension movement does not cause adverse changes in handling or grip.

An element of chassis tuning. Each tire can be tilted inward or outward depending on the track. The usual idea is to tilt the top of the tire inward (negative camber) so that under cornering loads, the entire surface of the tread is being used to the maximum. On oval tracks, because the car only turns left, the left-side tires may be tilted outward (positive camber). Teams adjust the camber setting based on reading tire temperatures across the surface of the tread, with the goal of having equal temperatures on the inside, middle and outside edges. Equal temperatures across the surface of the tire indicate the tire is being used to its maximum capacity.

Carbon fiber is lighter than aluminum, stronger than steel, and very expensive material. It's used to construct the chassis of a modern open wheeled car. Sheets of carbon fiber cloth are "laid up" like fiberglass by an expert fabricator using a mold, and then heated and reheated for days in an autoclave, a large, high-tech oven.

Another measure of chassis tuning related to the front wheels. The front wheels are attached to the suspension at the top and bottom of the wheel assembly. The top attachment is typically set a little farther back than the lower attachment, creating caster. The more caster used, the more the wheel resists turning forces, providing stability. Too much caster makes it very difficult to steer, and causes the tire camber to change significantly as the wheel is turned. Not enough caster results in the front end "wandering," or trying to turn on its own.

When the track is unsafe because of an accident, debris or a sudden downpour, the officials may put the track under caution by waving yellow flags at the starter stand and around the track. This brings out the pace car to gather the field and lead them around at reduced speed until the track is safe for a restart.

The basic structure of a car, including the driver tub, gearbox and suspension. Engines are provided separately.

This black-and-white checked flag is the most famous in racing, signifying the end of the session or race. At the end of a race, the first car to receive the checkered flag at the finish line is the winner.

A quick succession of sharp, slow turns, usually intended to reduce straightaway speeds.

Any time cars are on the racing surface, the chief steward is in charge of the entire facility. He is stationed in race control with radio communications all around the circuit, and he also has at his disposal a full bank of television monitors that give him a view of the entire circuit.

When a car is running by itself on the track, it's in "clean air" because the air is not being disturbed by other cars. See Dirty air.

Tires are extremely important in racing. Compound refers to the chemical composition of the rubber tread, which requires a balance between the conflicting goals of traction (soft compound) and durability (hard compound).

This refers to the distribution of a car's weight among the four wheels. Management of corner weights is very important to handling. This weight is usually adjusted through raising and lowering each corner by rotating a threaded spring perch on each shock absorber or at some other point in the suspension linkage.

Acronym for "Data Acquisition Geek," a computer expert who maintains a team's Data Acquisition system and analyzes the data.

Teams use sophisticated sensors, transmitters, computers and software to provide information on what the car and the driver are doing. Everything from engine stress to the driver's heartbeat can be monitored. The information is analyzed to improve handling, performance and even driver technique. Data can be acquired by connecting a computer to the car or by wireless telemetry.

The bodywork at the rear underside of the car that controls underbody airflow as it exits the back of the car. A good diffuser generates significant downforce.

The rear wing of the car in front tends to push the air higher, creating a very turbulent low-pressure area directly behind the car. At high speeds, downforce can be disrupted by following closely behind another car. A car following closely often will suffer understeer as a result of being in this "dirty air."

Wings on a racing car are upside down compared to an airplane wing. Instead of lifting the car, they press the car harder onto the track, providing increased traction for braking, acceleration and cornering. Downforce is also provided by the ground-effects tunnels underneath the car, creating a vacuum that sucks the car to the track. A modern open wheeled car provides so much downforce that it could actually stick to the ceiling at just over 100 miles per hour. Increased downforce also results in increased drag, which slows a car down, so it's a tradeoff.

A fast-moving car creates a low-pressure area behind it, causing the air to try to move with the car. A car following behind can take advantage of this low pressure as it actually sucks the car along faster, known as "being in the slipstream." A savvy driver can either use the draft to pass, or to lift off the gas slightly and conserve fuel.

A contraction of "Dynamometer," an engine-testing device used in the shop that measures power and simulates the loads and environment of a racing engine.

Flags signal drivers of events or conditions. Green, white, white/red, black, checkered, blue, yellow, red and red/yellow flags each have a different meaning. See each individual color for an explanation of what each flag means.

If a driver locks a tire (brakes so hard that the wheel stops turning), he'll grind a flat spot on the surface of the tire. This causes vibration that can make the car almost undrivable.

Formula cars must fit within a specific set of design rules or "formula." The formulas are usually quite complex, but basic issues include minimum weight, engine displacement, vehicle dimensions, wing sizes and placement, ground-effects tunnel size and configuration, tire and wheel size, and safety considerations.

The transmission attached to the rear of the engine. Open wheeled cars have "sequential" shift patterns, which is more like a motorcycle gear change than the traditional "H" pattern on most street cars.

The green flag is used by the starter to signal drivers that the race is under way, either at the start of the event or at the conclusion of a full-course yellow flag condition. Green flags are used by corner workers on road courses to let drivers know that they have passed beyond a yellow flag area and may resume passing.

The starting order of cars, as determined by qualifying position.

see Line.

In airplanes, this refers to a cushion of air that builds up as a plane nears the ground. In racecars, this refers to artificially generated low-pressure areas underneath the car that help it adhere to the ground. This is done by "tunnels' on each side of the bottom of the car, which start off small near the front and gradually get bigger towards the rear, creating a vacuum as the car moves forward using the ground as the fourth side of the tunnel. The specifications of these ground effects tunnels are carefully monitored. Rules specify the dimensions of the tunnels and how high the outside edge of each tunnel must be from the ground. The greater the gap between the tunnel side and the ground, the more air escapes and the less downforce is generated.

 On the front and rear wings there are often small vertical strips along the trailing edges of the wings, set at 90 degrees to the plane of the wing. Because these strips greatly reduce turbulent air behind the wing, they can add significant downforce with a minimal amount of drag. On the rear wing, it can be easily exchanged for a different size during a pit stop. American racing legend Dan Gurney is generally credited with creating this device, which is also known as a "wickerbill." 

A sharp, 180-degree turn.

A tire that has been heated up through use and then cooled down has experienced one heat cycle. This often results in a slight hardening of the tire compound, which can make the tire perform at a high level for a longer period of time. See Scrubbed Tires.

A measure of an engine's maximum output in terms of torque over a period of time. open wheel car engines produce around 900hp.

The area inside the boundary of the track.

A brand name for a certain type of carbon fiber, used in everything from driver's helmets to bodywork to bulletproof vests used by police. A very strong, expensive and lightweight material.

This term describes two things: the absorbent powder used to soak up fluid spills on the track (often real kitty litter) and the gravel runoff areas on the outside of many road course turns that help slow cars that go off the track.