The following is provided for information only. Driving or riding can be a dangerous activity, what you do on your own time with your own vehicle is up to you. Always drive / ride safe and never do anything that would endanger pedestrians or other motorists. The roads belong to everyone; make sure that you, and everyone you pass, makes it home safely. By using this site you agree to release from any liability resulting from your actions.

The following defenitions are in my own words where possible, but when I needed help I used Road and Track Illustrated Automotive Dictionary, John Dinkel, © 2000.


Apex - An apex is the point at which you get closest to the inside of corner. On racetracks there is typically a section of pavement on the inside of corners that is painted red & white, this is where the apex is. By "making" the apex farthur into a corner it allows you to have a straighter line on your exit, which allows for more room to accelerate.

Bias-ply tire new - An older method of tire construction where steel cords (plies) were laid at angles to the direction of travel so they overlapped.

Blow off valve - Officially known as a wastegate; a valve used on turbochargers to allow the engine to get rid of excess pressure generated by the turbos in the lines. Prevents the engine from damaging itself.

Brake fade - The loss of braking force, typically due to heat

Caravan - To drive together as a group to a mutual destination. Typically used when describing a smaller group going together to meet the whole group for a drive.

Center of gravity (cg) - The point in an object where the weight is assumed to be for design calculations. In a car the lower the better.

Chassis - A car without the body, trim, and accessories; just the frame and mechanical pieces.

Coefficient of drag (cd) - A measure of how aerodynamic a car is. The lower the number the better, typically around 0.3 for a sports car.

Coil-over - A type of suspension where the spring and shock are incorporated into one unit that allows for easy raising and lowering of the ride height of the vehicle. These are best used for cars that are driven on the track and on the roads.

Cold air intake (CAI) - Essentially a pipe with an air filter on the end that draws cold air into the engine. Colder air allows the engine to generate more power than warm air.

Continuously variable transmission (CVT) - A non-automatic transmission that has a system of belts and pulleys that alter the transmission ratio depending upon speed and power demands. This allows the engine and throttle to maintain in one spot, keeping your car in its ideal power band.

Cornering limit - How fast a car can travel around a corner.

Corporate Average Fuel Economy (CAFE) - U.S. Government-mandated fuel-economy standards. Put simply, the average fuel economy of the vehicles sold in the United States by a manufacturer in a given year must equal or exceed the standard for that year. If it doesn't, the manufacturer gets fined per vehicle sold per 0.1-mpg deviation. What this means to us is that if a car company sells a sports car that gets 11-mpg, then it also has to sell an economy car that gets 30-40-mpg to average out the results. This is why many sports cars have a "gas guzzler" tax, because that manufacturer doesn't make an economy car and so must pay the penalty.

Coupe - A two-door car with a fixed metal roof. These cars are typicaly considered "sexier" and sportier than their 4-door counterparts, they are also usually much stiffer and therefore perform better.

Crush Zone - The areas at the front and rear of the car designed to absorb the impact in an accident and keep the damage from reaching the passenger compartment.

Curb weight - The total weight of a vehicle ready for sale, with all fluids but without driver or passengers.

Donut (1) - Slang for a temporary spare tire. Many people don't realize that these are a one time use tire, designed for a maximum speed and maximum distance, usually specified on the tire itself.

Donut (2) new - A controlled spin in a car or motorcycle, where the driver/rider spins the vehicle in circles at high RMP, which typically leaves tire marks on the ground in the shape of a circle or donut.

Double-clutching - A driving technique in which the driver depresses the clutch pedal, moves the shift lever out of gear and into neutral, releases the clutch pedal about halfway while simultaneiously using the throttle to increase engine speed, then depresses the clutch pedal again while shifting to the desired gear. This is done to minimize gear clash or grinding, but on modern transmissions with syncrhomesh gears it is not as important as it used to be. This process is part of heel-toe shifting.

Downforce - Downward air pressure, generated by a car's body, that pushes the car onto the road with increasing force the faster it is driven. Spoilers, splitters, and wings are usually used to generate downforce, but high-end modern sports cars are designed in such a way to generate downforce without exteraneous body parts.

Drafting - A driving technique, typically used in racing, where one car closely follows another in order to drive without wind resistance, this being done by the lead car. This allows a driver to match the speed of the lead car without using as much of the engine's power and therefore saving fuel.

Drive by wire - The use of electronics to replace mechanical links in systems such as steering and throttle.

Dry sump - An oil lubrication system where the engine's oil is pumped from a different container than the crankcase. This is used on high-performance cars because it prevents oil starvation caused by constant high-speed cornering where a traditional oil pump can not feed oil to the engine.

Dual overhead cam (DOHC) - An engine with two overhead camshafts; one to operate the intake valves and one to operate exhaust valves.

Esses new - Slang for "s"-curves, or a series of slight curves back-to-back.

Estate car - European term for station wagon.

Firewall - The partition between the engine and passenger compartments.

Fish-tail new - When the back end of a vehicle is sliding from side to side, typically due to the driver losing control on a wet or loose surface. This can also happen in a rear-wheel drive vehicle with a lot of power.

Forced induction - An engine equipped with a turbocharger or supercharger that forces air into the cylinders.

Four wheel drift - A car cornering with its fron and rear tires sliding in a corntrolled manner. Basically a car sliding sideways under driver control.

G - Acceleration exerted on a body by earth's gravity. A force of 1g equals the weight of the body at rest, 2 g's exerts a pull equivalent to twice body weight, and so on. G-force can be used to acceleration and braking but is more commonly used for measuring a car's gip in corner. Hence the name Lateral G. A car that can exceed 1g of lateral grip is an amazing car with amazing tires.

Gran Turismo (GT) - Italian for Grand Touring, a sports car with a fixed roof, not a convertible. GT cars are also usually larger and heavier due to more emphasis on luxury that a "pure" sports car. The new Bugatti Veyron would be considered the ultimate GT.

Ground Effect - Result of the partial vacuum between the road surface and the undercarriage of an automobile. This gives the car better cornering ability but usually hurts top end speed.

Heel-toe - A driving technique where the driver applies pressure to both the gas pedal and the brakes at the same time with the right foot. This is to allow the driver to use the clutch with the left foot while breaking and matching RMP's so when he downshifts for the corner the engine speed will match the drivetrain and allow smoother shifts. It also prevents unwanted weight transfer throughout the car. This can be accomplished by using the toe of your shoe on the brake with your heel on the gas (hence the name), or by using the brakes with the left side of your foot and the gas with the right side.

High-side new - A motorcycle crash where the rider is thrown from the bike when the motorcycle slams its side into the ground. This type of accident usually results in broken arms and shoulders, and commonly happens when the rear tire loses traction and gets out of line with the front tire, similar to "fish-tailing" in a car.

Homologated - A racing term for a production car that has been certified for a specific class by a racing organization.

Horsepower new - A general term of the power output of an engine in a car or motorcycle. While not a scientific unit of measurement, it is still commonly used in the motorsport area as a method of comparing different vehicles. One source of confusion is how to measure, the horsepower at the engine's crankshaft (before it meets the transmission) will be higher than when measured at the wheels due to friction loss. American horespower measurements are defined as SAE, while in Europe they are defined as DIN; these two measurements are very close but do not exactly cross over.

Intercooler - A heat exchanger typically used on turbo and supercharged engines. Basically a type of radiator, it cools the air forced into the combustion chamber.

LEO new - Law enforcement officer.

Lift-off oversteer new - Oversteer caused when the driver lifts off the throttle while in a turn, reducing acceleration, and increasing grip on the front tires which increases their ability to turn. This then causes the vehicle to increase its rate of turn in to the corner.

Long block - A completely assembled engine, including all internal and external components. Ready for installation into a car.

Low-side new - A motorcycle crash where the rider is is dropped to the ground when the back end of the bike slides out. This is a common type of motorcycle crash in a curve and usually doesn't cause much damage to the rider, provided they are wearing proper gear and are not hit by another vehicle.

Mass airflow sensor - Part of the fuel injection system that measures the amount of air entering the engine to tell the computer how much fuel to inject.

Monocoque - A type of car construction that doesn't use a frame, but instead uses a rigid body shell for structural support. Very expensive but very lightweight and strong.

Naturaly aspirated - An engine that does not used forced iduction, i.e. turbos or superchargers.

Original equipment manufacturer (OEM) - Any company that makes automobiles, as well as companies that make parts that are installed during the construction of a vehicle.

Opposite lock - The act of turning the wheel the "wrong way" into a skid to straighten the car.

Oversteer - A condition where the rear tires of a car loses traction before the front. While this is good for an experienced driver can drive faster in a car that has neutral or oversteer, it is more dangerous for inexperienced drivers due to the car's desier to spin at the limit.

Pillars - A, B, C, D - The upright sections of body that connect the roof to the lower part of the car. Put simply, the sections of frame that block your view between windows. The front two are the "A" pillars, between the front and rear doors are the "B", behind the rear seats are the "C", and in a station wagon the two at the rear of the car are "D" pillars.

Racing line - Essentially, the fastest way through a corner or series of corners. This is great for a racetrack where you can use the entire width of the pavement but not so great for public streets that may have oncoming traffic. Typically the fastest way through a corner is by entering from the outside, just clipping the Apex of the corner, and ending on the outside of the pavement to "straighten" out the corner as much as possible.

Radial tire new - A newer method of constructing tires than bias-ply, where the steel cords (plies) are laid perpendicular to the direction of travel and do not overlap.

Ram air - A low grade supercharger where a hood or front air scoop forces cold air into the fuel injection system. Most commonly seen on modern Firebirds. These system are really only affective at higher speeds when the airflow is fast enough to increase pressure inside the cylinders.

Redline - The point on your tachometer (RPM guage) that indicates the point at which it is not safe to rev the engine past.

Rev limiter - A device which prevents your engine from rotating faster than its designed safety maximum. Prevents the engine from damaging itself.

RPM new - Revolutions per minute, how fast the engine "spins" each minute. Diesel trucks usually have a max abount 4,000rmp, passenger cars 6,000rpm, sports cars 8,000rpm, and motorcycles 15,000 rmp.

Saloon - British term for a four-door, fixed roof car with a trunk. Basically a standard family car.

Sequential manual gearbox - A manual gearbox without a manually controlled clutch pedal. You shift up or down in order, there is no ability to skip gears. Using a stick like an automatic or paddles on the steering wheel, the driver inputs an upshift or a downshift and the transmission's computers actuate the clutch and shift very quickly. Traditionally used in racecars, starting to become common in sports cars.

Short block - An engine block with all internals included, such as pistons, cams, crankshaft, etc.; but does not have any external pieces such as alternator, wiring, distributor, etc.

Shooting brake - British term for station wagon.

Sill - The portion of the frame underneath the doors. What you have to step over to enter a vehicle.

Slush box - Slang for an automatic transmission, due to their tendancy to rob torque.

Spider (or spyder) - Term for a convertible, 2-seat car.

Spin new - When a vehicle rotates around its own axis (or the center of the vehicle). Typically this results in the loss of control of the vehicle, and can happen on ice or slippery surfaces or when a car loses traction in a corner.

Splitter new - Device located below the front bumper of a car, used to provide downforce.

Spoiler - An aerodynamic device, most typically on the rear deck but also used under the front bumper to reduce drag or increase downforce. Called spoilers because they "spoil" the airflow around a vehicle, many people claim they "spoil" the looks of the vehicle as well. Most commonly seen as a large wing bolted to the truck lid.

Tachometer - The guage on your dashboard that measures RPM (rotations per minute) of your engine. Most commonly used on manual cars to tell the driver when to shift.

Targa - A type of convertible invented by Porsche where the center section of the roof may be removed for a partial convertible effect or replaced for a coupe effect.

Tire sizes new - Tires come in a large variety of sizes and styles, but each tire will have the specifics of its construction printed on the sidwall. Some off-road truck tires use a more simplistic system, but most tires have a number which will look something like 205/55 [R] 17 88V. The first number, 205/55, is the width of the tire in millimeters over the ratio of tire width to sidewall height. The letter, [R], indicates that the tire is of radial construction. The next number, 17, is the inside diameter of the tire (or the size of the wheel it is mounted on). Finally, in the last set, 88V, 88 is the maximum load rating and the V is the speed rating.

Tire speed ratings new - All new tires sold must be able to maintain 85mph, but high-performance tires are designed for much higher speeds. As described above each tire will be marked with its speed rating, or the maximum speed the tire must be able to sustain without failure. The ratings are; S = 112mph, T = 118mph, H = 130mph, V = 149mph, W = 168mph, Y = 149mph, Z = 150+mph.

Torque new - A rotational force around a fixed axis, such as a wrench turning a bolt. Torque is what gives vehicles acceleration and pulling power, such as a large truck towing a trailer.

Torque steer - A trait of some front wheel drive vehicles to pull to one side during acceleration. This is commonly due to the driveshafts being unequal in length. The more power the car has the more likely to experience the problem.

Turbo lag - The time between when the driver steps on the gas of a turbocharged car and the time when the turbo's effort reaches the engine. This is due to the turbo having to spin up to operating speeds to generate thrust.

Turns lock-to-lock - The number of times the steering wheel must be turned to go from extreme right to extreme left. The fewer number of turns the more agile a car will be in tight corners, but harder to maintain on high speed cruising in a straight line.

Understeer - Basically, the front tires of the car runs out of traction before the back of the car. Most production cars are designed with a certain amount of understeer as this is considered safer than the back of the car losing traction first and spinning out.

Unsprung weight - In practical terms, the weight of the car that must be pushed to the ground by the suspension. The wheels, tires, brakes, bearings, etc.

Weight transfer - The affects of acceleration, deceleration, cornering, or a combination of these on the suspension of a vehicle. When a car accelerates weight is "transfered" to the rear tires, upon deceleration the transfer is to the front tires. This is an important fact to keep in mind when cornering because the more weight that is transfered to a particular tire will give that tire more traction. Hard deceleration while in a corner will transfer weight to the front tires, provide more traction, and may case the vehicle to oversteer - possible causing a spin and even an accident.

Wheel hop - A condition where rough or uneven surfaces cause the tire to completely leave the ground. This is commonly due to worn shocks or an improper suspension setup. This can be extremely dangerous, as the vehicle looses 25% of its cornering and braking ability for every tire not on the ground. This can be seen quite frequently on older cars on concrete freeways with expansion joints, the tire is visibly bouncing up and down as the car moves.

Xenon headlights - A headlight assembly that does not use a bulb, but instead creates an arc of electricity through a gas in a sealed container. Similar to a traditional movie projector.

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