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Short for aerodynamic. Aero adjustments on a racecar affect the behavior of the car in the speed range where the flow of air is fast enough to create down force on the tires.
ANGLE OF ATTACK
The angle of an aerodynamic device relative to the air stream. If not excessive, increases in angle of attack create more down force and drag.
The clipping point on the inside of a corner where the car is at the correct angle for a perfect exit onto the next section of track.
The relationship between a tire’s sidewall height and it’s tread width. Smaller aspect ratios describe a tire that is low profile and wide, verses tall and thin.
The mix of front versus rear grip that is determined by chassis, aero and brake-bias settings. Chassis settings, as well as acceleration and braking, influence handling at all speeds. Aero adjustments affect balance mainly in high-speed turns. Brake balance determines which tires lock up first.
Excess steering angle limiting a car’s acceleration.
Proper downshifting technique requires that the engine revs be increased to allow smooth engagement of the next lowest gear, and to match engine speed with road speed. The "Blip" is a quick application of the throttle pedal, usually done using the heal and toe technique, to momentarily increase the engine RPM.
The relative proportion of braking effort on the front or rear of the car. In most modern racecars, brake bias is adjustable to compensate for changes in track conditions, fuel load, and aerodynamic down force.
A specific reference on or next to the track which drivers use to start the application of brakes. Smart drivers start with a conservative brake point and move it closer to the corner until exit speed is compromised. This is called “The Procedure to Find the Braking Point.”
Combining the car`s braking and turning abilities simultaneously in the area beyond the turn-in point. This is a very efficient use of a tire’s traction capability and enables the driver to safely brake later. It also helps the car turn-in to a corner.
BREATHING’ THE THROTTLE
A lift (in varying degrees) off the throttle to neutralize under steer or induce TTO.
Co-efficient of friction: A convenient way of comparing the grip of tires from one to another. It is a measure of the ratio at which a tire converts downloading to traction.
(Cg) Center of gravity: The point in space where the car`s mass is centered.
Abruptly turning into a corner to prevent a pass.
Flag requiring action on the part of the driver.
A corner where you compromise or modify your line to gain or benefit in another corner.
CONSTANT RADIUS CORNERS
Turns which can be measured with one arc starting at the turn-in point.
That part of a tire that’s in contact with the road at any one point in time.
The section of track between the brake point and where throttle application starts.
The first phase in handling a slide (CPR) is the "Correction." The driver looks where he would like to go and turns the steering wheel toward the direction that rear of the car is sliding.
driver`s Safety Rating is derived from their Corners Per incident (CPI) average. Each track has a set number of corners. For example Lime Rock Park has seven corners. If you get one incident point every lap, your CPI would be seven. If you drove 100 laps, with only one incident, your CPI would be 700.
A skid-control technique involving the Correction, the Pause, and the Recovery.
Gradually drifting toward the inside of the road and sacrificing radius on the approach to a corner. Crabbing is a symptom of low eyes and slow hand speed, and results in an early apex.
The technically correct term for “shock absorber.” It dampens the frequency of a spring’s motion; it does not support the weight of the car.
DECREASING RADIUS CORNER
A corner where the first section of the turn has a larger radius than the second.
Going to the brakes as close as possible to a corner.
An ill-advised, late attempt at a pass.
A downshifting technique used to manually speed up the main-shaft in a non-synchronized transmission. Does not apply to sequential gearboxes.
Using the slipstream to approach and pass other cars. Also known as “tow.”
The act of driving with one or more wheels of the car off the race track.
Skipping gears when downshifting. Typically going directly from top gear to first rather than downshifting through each gear.
An early apex requires additional steering input beyond the clipping point of a corner. This is generally the most common line mistake, but “early apexing” can be used if there is an increase in elevation and/or cornering grip after the apex.
The speed of a car at the track-out point of the corner.
Moving the steering wheel quickly.
Used to communicate with the driver.
Never lifting off full throttle. Also, defined as driving absolutely at the limit, leaving no margin for error.
CIRCLE A graph used to show a tire’s maximum capabilities in the three forces it can generate: Braking, Cornering, Accelerating.
The measure of force that gravity exerts on earth. It is used as a reference point to compare the lateral acceleration forces that cars generate during braking, turning and accelerating.
Starting positions for the beginning of a race.
The traction of tires in braking, turning and accelerating. Generally measured in units of “G” (g).
A relatively slow corner with more than 120 degrees of direction change.
HEEL AND TOE
The process of keeping consistent pressure on the brake pedal while blipping the throttle for downshifts. This technique is actually a misnomer (it has historical equity, however) since modern pedal layouts enable the use of the ball of the foot on the brake while at the same time using the right side of the same foot to rev (blip) the throttle. This is an essential skill that all great drivers use to shorten braking zones and turn fast laps.
A spin generally to the inside of a turn. This is the most common spin in racing. Differs from a “second reaction hook-slide.”
The second-reaction slide.
INCREASING RADIUS CORNER
A corner where the radius of the early part of the corner is tighter than the radius of the later section.
Track advisory flags.
Your iRating is a measure of your skill as compared to other iRacing.com drivers. iRatings are used to ensure simularly skilled drivers compete against each other in official sessions and Race Series.
A jog in the road, normally found on part of a straight.
iRacing.com`s unique system that can take drivers from a racing school all the way up to motorsports top ranks
A clipping point on the inside of a turn that permits a decrease of steering angle during the second half of a corner. Generally used to permit acceleration, especially if grip is decreased for any reason in the last part of a turn.
A method used to learn the racing line, where the driver follows an instructor around the race track.
Coming off or reducing throttle.
The optimum path around the racetrack. The line can vary with track conditions and the type of racecar being driven. Other variables include elevation change, pavement change, and how well a car turns-in to a corner.
The change in the vertical down force on a tire that results from braking, turning or accelerating.
Occurs under braking, when a tire stops rotating. Loss of steering control, flat spotted tires, and a 30% decrease in braking traction are the results of lockup. Causes include over-braking, improper brake bias, or crabbing the entry into a corner.
Synonymous with over steer.
Throttle application intended to maintain the current speed of the car, and thereby settle the balance of the chassis.
Changing the pressure on the brake or throttle in an effort to keep the tires near, but not over, their traction limits.
When both front and rear sets of tires operate in the same slip-angle range when a car is cornering at the limit.
Braking later than another driver.
High RPM in a range that is likely to cause damage to an engine’s internal components.
OVERSTEER Synonymous with “loose,” it’s when the slip angle of the rear tires is greater than the slip angle of the front tires when a car is cornering at the limit. Numerous types: Steady state, trailing throttle, trailing clutch, power, brake bias, and aerodynamically induced over-steer are all examples. Another description: The car is turning more than the steering input or radius would dictate.
The warm-up lap prior to a race start.
During a skid, that moment when the movement of the rear of the car toward the outside stops. The springs are about to rebound and transfer weight toward the inside tires. This precedes the Recovery phase of CPR. Also described as the moment during a skid when the rotation of the spin is “caught” and converted to a sideways slide.
Adding steering input to a car when it’s cornering. Most frequent in the second half of the corner to recover from an early apex, adding acceleration too soon or a poorly timed pass.
PIT LANE/HOT PITS
An area adjacent to the racetrack where cars are worked on during practice, qualifying or a race. “To pit” means to make a pit-stop.
Changes of the front-to-rear ride height; also, the angle of attack of a car in response to acceleration and braking.
The fastest qualifier.
Recovery is the third phase of skid control (CPR). As a slide stops, the outside springs unload, transferring weight to the inside tires. Good drivers know that they must straighten the steering wheel to prevent a second-reaction hook-slide.
The maximum RPM depicted on the tachometer that an engine can turn without damage to its internal components.
Any point on or beside the racetrack which a driver uses to trigger some action; turning in, apexing, brake application point, etc.
Term used to describe the RPM (revolutions per minute) of the engine. Short for revolution.
The angle of the road surface relative to the horizon. Positive road camber (“banking”) helps the car`s cornering force. Negative camber reduces the grip of the car.
The upward or downward movement, left or right along a car’s centerline, in response to cornering forces.
A point in space determined by suspension geometry that the CG rolls around at each end of the car.
Deliberate over-steer caused by the release of the brakes during the trail-braking phase of brake turning.
Revolutions per minute.
Sports Car Club Of America, a sanctioning body.
The rebound of the chassis toward the inside springs after a slide stops. Must be countered by the Recovery phase of CPR to prevent a hook-slide.
The time it takes to drive from point to point on a section of racetrack.
A fast shifting, constant-mesh, motorcycle-type gearbox that shifts directly to each gear without going through neutral.
Street tires can be shaved so that their tread depth is greatly reduced to make them race-ready. This prevents the tire from overheating and provides more traction.
A visual template that drivers use to locate themselves precisely on the racetrack. After using The Procedure to Find the Line, a driver takes a visual snapshot of each turn. He/she now will know where to be in every turn and be able to catch mistakes early.
While cornering, there is a difference between the direction that the centerline of the wheel is pointing and the direction that the tire is traveling. This difference is measured in degrees and referred to as slip angle. Tires have a range of slip angles where they deliver their maximum level of cornering traction.
The area of clean air behind a moving car. Also defined as following closely in the draft behind other cars.
The opposite of “fast hands.”
At the start of the race, the tendency for all the cars to arrive in the first turn at the same time.
The maximum degree of steering input available on a car.
Self-explanatory, except that if the portion of the circuit can be driven as fast as the car can go, the road doesn`t necessarily have to be perfectly straight to be considered part of the straight-away.
An adjustable suspension device at one or both ends of a car that limits weight transfer. Some are cockpit actuated. Sway-bars control the rate of chassis roll relative to the suspension.
A fast, “sweeping” corner.
Device for measuring engine speed in revolutions per minute (RPM).
Too Fast, Too Soon.
The method of working your way up to the limit by starting off conservatively and taking small, incremental steps to increase your speed.
Using 100% of a car`s braking capability while braking in a straight line. At the “threshold" limit, the tire will be revolving approximately 15% slower than it would be if freely rolling over the road.
The “gas pedal.”
THROTTLE APPLICATION POINT
The point in a turn where a driver begins to apply power to drive away from the corner.
Synonymous with under-steer and “push.”
TIRE PERFORMANCE CURVE
A graph to show a tires grip and slip angle are related.
The point that the car touches the outside edge of the road at the exit of a corner. Or the point in a corner when the hands are straight and there is no cornering load.
A gradual release of the brakes during brake-turning that leads to “rotation” at the limit.
TRAILING THROTTLE OVER-STEER (TTO)
Over-steer caused by lifting off or “trailing” the throttle when the car is near its cornering limit.
The point at which the driver first turns the steering wheel, transitioning the car from the straight into the corner.
TYPE ONE TURNS
Corners that precede long straights. These are the most common types of turns and generally require a late apex to maximize exit speed.
TYPE THREE TURNS
Set-up (or “compromise”) turns. Always precedes Type One Turns. These are the most challenging corners since you must know where to go slow to turn a fast lap.
TYPE TWO TURNS
Corners that come at the end of long straights where carrying entry speed produces a better lap time.
Synonymous with “push” and “tight.” The slip angle of the front tires is greater than the slip angle of the rears when the car is cornering at the limit. The car is turning less than the steering input or radius would dictate.
Also Known as “Load Transfer.” The lateral and longitudinal movement of the mass of the car as determined by the driver’s inputs.
The angle between the centerline of a car and the direction the car is traveling when cornering.