1stGenCRXer

This is by no means intended to be a 100% complete list of terms used in racing, so feel free to add any you feel are missing. There is no real order to this list, so go ahead and read it all

oversteer- Also known as being "loose." This is used to describe how the rear of the car has a tendency to try and pass the front of the car. The rear tires lose traction while the front tires do not, and so the rear is "loose" and chasing you all over the place.

understeer- The opposite of oversteer, also known as being "tight." In this case, the car wants to continue travelling forward regardless of how much or little the front wheels are turned. The rear tires are holding mroe traction than the fronts, and are holding "tight" to the road, causing the front tires to plow instead of turn and rotate the car.

apex- The apex is the ideal point that a driver wants to aim his car on the inside of a turn to maximize the turning radius, and thus the carried momentum and speed that the car will be able to maintain. [to be discussed more in a later thread]

unsprung weight- Refers to any drivetrain item that is attached to the chassis of the car solidly. In this manner, the spring and shock combination is not required to deal with the weight of those items in order to articulate over bumps and during loading. Less unsprung weight allows for faster suspension movement with less spring rate, and can eliminate the tendency of a vehicle to bounce while the inertia of the sprung weight overpowers the spring and dampening rates.

rotational inertia- Refers to any rotating item in the brakes or drivetrain. The inertia of these items dictate how quickly the car can be slowed, and how quickly they can be accelerated. Other factors can manipulate the effect rotating inertia has on the performance as well.

polar inertia- Every car has a balance point, polar inertia is a combination of yaw rate, forward grip, and lateral grip of the tires during a turn or high speed run. As the yaw rate is increased [or attempted to increase], if the lateral grip of the tires can't keep up, the car will just slide to the outside of a curve. At the same time, if the yaw rate is controllable, but the lateral grip is too low, forward grip can sometimes be used to increase the yaw rate of the car while reducing the outward slide. Polar inertia is the tendency of a particular car to be very controllable at the limits of adhesion [low polar inertia], or to be very twitchy and unpredictable at the limits [high polar intertia]. Cars with low polar inertia tend to be rear wheel drive and favorites for drifting. A neutral car can be controllable up to the limit and unpredictable over the limit depending on how it is driven.

stagger- The difference in tire circumference from across the car either in the front or the rear. With a larger tire to the outside of a turn, the car's natural tendency will be to "wander" in the direction opposite of that larger tire, and while not linear in effect, the larger the differential, the greater the wander effect tends to be. Think of it as turn banking built into your car.

camber- Measured in degrees from perpendicular to the ground against the centerline of the wheel in line with the center of the wheel. The amount of "tilt" either inboard or outboard of the wheel is the camber, with negative camber being a "top in" orientation. The idea behind camber is to angle the wheels so that at full load in a turn, the full width of the tread will be in contact with the track. This also helps straightaway speed since tires work because of friction, and a tilted tire has less surface contact with the road when not being loaded laterally.

caster- Measured in degrees from perpendicular to the ground against the centerline of the kingpin or whatever steering centerline the front suspension uses. Caster determines how much weight transfer through the suspension there will be during a turn. Negative caster is towards the rear of the car, and is the standard direction of adjustment since it will cause the inside front tire to dig in to the pavement, and thus cross load the outside rear tire for maximum grip in the turn.

ackerman steering- Refers to the effect built into steering systems that causes the inside tire to rotate more in a turn than the outside tire, allowing the tires to follow the same arc at different radii so that the tires are rolling as opposed to fighting each other for control. This helps controllability in a turn, as well as reduces the unnecessary friction that would otherwise slow corner speed. [more on suspension geometry and handling in a later article]

jaje

the easy way to explain polar moment of inertia by example (made the most sense to me):

High Rotational Inertia: Take a 10lb dumbbell in each hand and hold the weights out away from your body to each side (you will look like a letter T)...spin in a circle at a moderate pace and then stop as fast as you can

Low Rotational Inertia: Next hold the dumbbell in as close as you can (you will look like you have chicken wings)...repeat the spinning process and stop as fast as you can

Notice the 2nd method (if done right) is much easier to stop...this is what a car feels when you are drifting or purposely trying to rotate the car for the maximum exit speed out of a corner

Fujiwara Takumi

define Lift Throttle Oversteer.

1stGenCRXer

lift throttle oversteer- the tendency of a car to oversteer when weight [and thus grip] is transferred off of the rear tires and on to the front tires, caused either under braking or sudden stop of power, as in lifting off of the throttle.

jaje

the 1st lesson a racer learns is not to lift throttle while cornering...b/c it transfers all the weight forward and reduces grip