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There is an enormous amount of terminology used to describe today's automobiles. In some cases, understanding
these terms is crucial to understanding and enjoying the various articles and vehicle reviews found on Car
Central. With this in mind, we've created the most comprehensive online automotive glossary. If you cannot
find the term you are looking for, please contact
us.
The roof support on either side of a vehicle's windshield. A-pillars are designed to support a large portion of the vehicle's weight in the event of a roll-over.
Active Suspension System
A computer controlled system that utilizes powered actuators in place of regular springs and shock absorbers. The computer controls the position and movement of each wheel's suspension to provide the best possible ride characteristics under varying conditions.
Additive
A substance added in small amounts to something. The most common types of automotive additives are fuel additives (such as fuel injector cleaner) and oil additives (such as friction modifiers). MotorUP®, DuraLube®, Slick-50®, and Prolong® are examples of popular friction modifiers added to motor oil.
Aerodynamic Drag
The resisting force produced by a moving object as it displaces the air in its path. Aerodynamic drag is usually measured in pounds.
Aftermarket
A term used to describe the various products and services used to repair, maintain, or upgrade vehicles. The term "aftermarket" is most commonly used to describe specialty auto body parts such as hoods, spoilers, and body kits.
Air Dam
A spoiler mounted beneath the front bumper of a vehicle and designed to alter the flow of air under the vehicle. Air dams are often used to increase the airflow to a radiator, decrease lift, and reduce aerodynamic drag.
All-Wheel-Drive (AWD)
A term used to describe vehicles where all four wheels are driven by the engine. All-wheel-drive vehicles generally have better traction than two-wheel-drive (2WD) vehicles. All-wheel-drive differs from four-wheel-drive (4WD) because it can be used under any road conditions.
Alloy
A metal that contains one or more other elements usually added to increase stength or give the base metal important properties. Alloy wheels are commonly made of a combination of aluminum (for its light weight) and steel (for its high strength).
Alternator
An electric generator that produces alternating current (AC) but is rectified to direct current (DC) by diodes. An alternator converts the rotating motion of an engine into electricity to power a vehicle's electrical components and keep its battery fully charged.
Ambient Air Temperature (AAT)
The temperature of air surrounding an object. The computers on some vehicles use this information to fine tune the engine's operation.
American Wire Gauge (AWG)
A system of measuring the size of wire. The smaller the wire the larger the gauge. For Example: 1-4 gauge wire is very thick and commonly used for high-current battery cables, while 14-18 gauge wire is very thin and commonly used for low-current wiring harnesses.
Angle of Approach
When viewed from the side; the line from the bottom of the front tire to the lowest-hanging component in front of the tire. This angle is an approximate indication of how steep an incline a vehicle can approach without damaging the front of the vehicle.
Angle of Departure
When viewed from the side; the line from the bottom of the rear tire to the lowest-hanging component behind the tire. This angle is an approximate indication of how steep an incline a vehicle can descend without damaging the rear of the vehicle.
Antidive
A suspension characteristic in which the downward force on the front of a vehicle, caused by the transfer of a vehicle's weight when braking, is resisted.
Antilock Brake System (ABS)
A computer controlled pump which varies the hydraulic pressure to each wheel's brake in order to prevent a vehicle's brakes from locking up. The computer distributes hydraulic pressure during hard braking based on the variance between the speed of each wheel (as measured by sensors at each wheel).
Antiroll Bar
A suspension component (used at the front and/or the rear) that reduces body roll by resisting any unequal vertical motion between the pair of wheels to which it is connected. An antiroll bar does not affect suspension stiffness when both wheels are deflected equally in the same direction. Antiroll bars are often referred to as Sway Bars or Stabalizer Bars.
Antisquat
A suspension characteristic in which the downward force on the rear of a vehicle, caused by the transfer of a vehicle's weight when accelerating, is resisted.
Aspect Ratio
A ratio between two measurements. Aspect ratios are most commonly used to describe the ratio between the height and width of a tire. A lower aspect ratio implies a shorter tire with a wider tread.
Automatic Transmission (A/T)
A transmission which automatically selects the appropriate gear without any input from the driver. Gears are chosen according to the speed of the vehicle and load on the engine. Automatic transmissions are either hydraulic or electric operated.
Automotive Service Excellence (ASE)
A non-profit organization for the testing and certification of vehicle service technicians. To be "ASE certified" implies a technician has passed one or more of the organization's exams.
Axle Articulation
The term describing the ability of an axle to move in varying vertical directions (left wheel up, right wheel down (or vice-versa)) relative to the chassis. It is a measure of the ease in which wheels stay in contact with the ground on an uneven surface.
Axle Ratio
The ratio between the number of rotations of a driveshaft to the number of rotations of the drive axles. Axle ratio is determined in gearing inside the differential.
Axle Tramp
A form of wheel hop that occurs on cars with live axles. Axle tramp is caused by the axle repeatedly rotating slightly with the wheels and then springing back.
