Glossary

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Even a hardened automotive enthusiast can sometimes be stumped by terminology. Automobiles are complex machines designed and built by many people. While basic concepts are the same, some ideas are known by many names. This is partly due to confusion by consumers, and marketing by the manufacturers. Use our Automotive glossary as a source of information. See something that isn't here, let us know and we will add it.

Accessory Drive Belts
A pulley attached to the engine crankshaft drives the accessory belts. These belts power the alternator, air conditioning compressor, water pump, and other engine systems that require power.
All Wheel Drive
All four wheels are driven by the engine. AWD systems are superior to 4WD because (AWD) they can be used under any road conditions. AWD systems use a center differential to allow the front and rear wheels to rotate at different speeds. AWD provides better traction than front or rear-wheel drive.
Alloy wheels
Wheels usually made of aluminum alloy; installed to improve appearance. Alloy wheels are less prone to corrosion and can be significantly lighter than the equivalent steel wheels.
Alternator
A device that converts rotational energy to AC current. Alternators provide energy for the vehicle electrical system. The alternator also recharges the battery.
Anti-roll bar Sway bar Stabilizer bar
A steel rod or tube that connects the right and left suspension members together to resist roll or swaying of the vehicle. An anti-roll bar improves the handling of a vehicle by increasing stability during cornering or evasive maneuvers. Most vehicles have front anti-roll bars. Anti-roll bars at both the front and rear wheels can reduce roll further.
Axle Ratios
The gear ratio of the differential gearbox. The differential gearbox distributes the engine's power (via the transmission input shaft or propellor shaft) to the wheels. The axle ratio of the differential reduces the revolutions of the transmission input shaft before it reaches the wheels. Typical automotive axle ratios are in the range of 2.7:1 up to 4.3:1. The higher the ratio, the faster the engine will rev at a particular vehicle speed.
Axle, Live or Rigid
A solid or straight axle that allows the movement of one wheel to affect the opposite wheel. A live axle is inexpensive to manufacture and is useful for heavy duty applications.
Ball Joint
Usually refers to the outboard(wheel) end of a CV joint(halfshaft). The ball joint allows the wheel to steer and move with the suspension and still receive power from the engine. The term ball joint can also be used to refer to how suspension components are attached.
Barrel
For automotive applications, the reference applies to carburetors. "2bbl." means that the carburetor has 2 barrels or venturi (or fuel nozzles). A "4bbl." carburetor has 4 barrels, etc. The number of venturi determine the amount of fuel that the carburetor can supply. A 4bbl. carburetor can usually provide more fuel than a similar 2bbl. unit.
Belts
Belts are used to drive many engine accessories. Most overhead cam(OHC) engines use cogged (toothed) belts to drive the camshaft(s). Belts drive the power steering pump, water pump, air-conditioning compressors, etc.
Brake Master Cylinder
The brake master cylinder is a reservoir for brake fluid. The master cylinder pressurizes the brake fluid, which actuates the brake calipers or brake shoes to slow the vehicle. A defective master cylinder can lead to a partial or total loss of braking capability.
Brakes, Antilock
An acronym for Antilock Braking System. ABS eliminates wheel lockup during braking and loss of steering control on slippery surfaces. Speed sensors monitor each wheel and reduce brake pressure on any wheel rotating significantly slower than the others. ABS systems are 2, 3, or 4-channel systems. 2-channel systems combine 2 wheels, such as the left front and right rear into one channel. The right front and left rear wheel form the other channel. Any wheel lockup causes brake pressure reduction on both wheels of each channel. 3-channel ABS systems combine the rear wheels into one channel. The front wheels have individual channels. The most sophisticated ABS systems use 4-channels, one for each wheel, for maximum control and braking power.
Brakes, Calipers
Brake pads are mounted to calipers, which float next to the brake disc. The caliper ensures that the brake pads exert even pressure on the disc.
Brakes, Disc
A brake that uses a disc shaped rotor and calipers that hold friction pads. The rotor is attached to the wheel hub and spins with it. The calipers are stationary. When the brake pedal is depressed, the calipers press on the side of the side of the rotor. The friction pads slow the rotor as needed. Most vehicles use disc brakes on the front wheels. Disc brakes can shed heat and retain their braking power better than drum brakes.
Brakes, Drum
A brake that uses an enclosed rotating drum or can and stationary pads(shoes). When the brake pedal is depressed, the brake shoes contact the sides of the can and slow the wheel. Drum brakes are usually mounted on rear wheels. Drum brakes are prone to fade, or heat buildup, which reduces their effectiveness.