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A arm

See also Wishbone

A suspension linkage formed in the shape of an A or V found commonly on the front suspension.

The sides of the two legs of the A-arm are connected to the chassis by rubber bushings and the peak of the A-arm is attached to the wheel assembly.

In this way, the wheel can freely move up and down.

Sometimes there is an upper A-arm, a lower A-arm, or both upper and lower A-arms.

A.B.S.

Abbreviation for Anti-lock Brake System.

The Abbreviation ABS comes from the German Anti Blockier System.

A computer, sensors, and solenoid valves work together to sense wheel speed in order to modulate braking force if wheels lockup during braking.

ABS can help the driver retain control of the vehicle during heavy braking on slippery roads.

It works on the principle of braking a wheel until it just begins to skid (this is the point where braking efficiency would drop off dramatically) and then releasing the brake pressure and re-applying the brakes.

Wheel speed sensors identify the skid point and trigger a release in brake pressure.

The cycle is repeated many times a second.

The driver will feel a rapid pulsing at the brake pedal and hear a chattering noise as ABS is applied

 

A.B.S. Warning Light

Indicator lamp mounted in the instrument cluster. It illuminates when there is a problem in the anti-lock brake system. It will also illuminate momentarily when starting the vehicle to indicate that the lamp is functioning.

Accelerator interlock

See also: Anti Gas

A connection between the gas pedal and the automatic transmission

Accumulator

See also: fuel accumulator, hydraulic accumulator, Pressure accumulator

A storage battery for an electric car.

A part of a hydraulic system filled with nitrogen gas and used to store high pressure fluid to provide pressure assistance for system operation.

A pressurised container for an automatic levelling suspension system.

A part of the hydraulic system which is charged by the fluid pump, absorbs fluctuating fluid delivery, stores fluid at pressure, and can provide a rapid flow of fluid under pressure.

A device in the fuel line between the pump and filter that keep up the fuel pressure when the fuel pump is off thus preventing vapour lock and excessive fuel pump noise in having to build up pressure when needed

A vessel that stores hydraulic fluid under pressure.

A storage tank which receives liquid refrigerant from the evaporator and prevents it from flowing into the suction line before vaporising.

A refrigerant storage device used on General Motors and Ford systems that receives vapour and liquid refrigerant from the evaporator.

The accumulator, which contains desiccant, performs a function similar to that of a receiver-drier it separates liquid from the vapour, retains the liquid and releases the vapour to the compressor.

Always located on the low side of the system.

Acid

See: Battery acid

Ackermann angle / steering

The Ackermann steering setup allows all wheels to rotate around a common turning point (CTP). To obtain this effect, the inside steered wheel must turn through a greater angle than the outside steered wheel, known as Toe Out On Turns (TOOT)

The Ackermann principle provides the required angular movement by inclining the track arm inwards, to the extent that theoretical lines drawn between the king pins (or steering axis), through the track rod ball joints, would meet in the centre of the rear axle when the wheels are in the straight ahead position.

Actuator

A device which controls or operates another device.

A regulating valve which converts a form of energy into mechanical motion to open or close the valve seats

A device which responds to an output signal from a computer.

The portion of a regulating valve which converts mechanical fluid, thermal energy, or electrical energy into mechanical motion to open or close the valve seats

An electrical mechanism for moving or controlling something indirectly instead of by hand, such as a door lock. The output device that the PCM controls such as solenoids, relays, fuel injectors and stepper motors.

See

Brake Actuator

Electrohydraulic Actuator

Feedback Carburetor Actuator

Hydraulic Actuator

Idle Speed Actuator

Spring Type Brake Actuator

A device which controls or operates another device.

A regulating valve which converts a form of energy into mechanical motion to open or close the valve seats

A device which responds to an output signal from a computer.

The portion of a regulating valve which converts mechanical fluid, thermal energy, or electrical energy into mechanical motion to open or close the valve seats

An electrical mechanism for moving or controlling something indirectly instead of by hand, such as a door lock. The output device that the PCM controls such as solenoids, relays, fuel injectors and stepper motors.

 

See

Brake Actuator

Electrohydraulic Actuator

Feedback Carburetor Actuator

Hydraulic Actuator

Idle Speed Actuator

Spring Type Brake Actuator

AdBlue

AdBlue is the registered trademark for AUS32, or Aqueous Urea Solution 32.5% that is used with the Selective Catalytic Reduction system (SCR) to reduce emissions of oxides of nitrogen from the exhaust of UK diesel vehicles.

Adjustable shock absorber

Shocks with adjustable bounce and rebound characteristics can be stiffened to compensate for wear or to fine tune a suspension for a particular application such as rough roads, heavy loads, or racing.

Manual types (especially on motorcycles) require that you physically make the adjustment from one level to another by rotating securing rings.

Automatic types are controlled by a computer as it senses particular changes in road condition.

Adjusting shim

A thin washer or plate which reduces or increases the clearance between two components (depending upon where they are placed). While some valves are adjusted by screws on the rocker arm, others are set by inserting a shim to make the same adjustment.

Aeration

Act of combining substance with air

A foaming of a liquid because air has been introduced into the fluid.

When it occurs in certain liquids, it decreases the efficiency of the liquid.

Air-assisted hydraulic brake system (Air Over Hydraulic)

A hydraulic-type brake system actuated by an air over hydraulic power unit.

Airbag (Supplementary Restraint)

A device which is part of the passive safety system. In the event of a collision, Sensors will cause the airbag to be deployed so that your head will be pillowed by the bag instead of hitting the dash or windshield.

Airbag (Suspension)

Air bags are used in place of conventional steel springs in passenger cars, and in heavy vehicle applications such as buses and trucks.

Air Brakes

A system of braking which is usually found on large vehicles in which compressed air pushes against a brake piston or diaphragm in order to apply the mechanical brakes to stop or slow the vehicle.

Air Dryer

A device for removing the moisture from air as it enters a vehicles air braking system.

By Panoha [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or FAL], from Wikimedia Commons

Air Filter / Cleaner

A device for removing impurities from the air which enters the combustion chamber.

Air filter restriction indicator

A system of braking which is usually found on large vehicles in which compressed air pushes against a brake piston or diaphragm in order to apply the mechanical brakes to stop or slow the vehicle.

Align

  1. The process of bringing two or more items into mating conjunction so that all the bolt holes and locating pins fit properly.

  2. The process of adjusting wheels and other components so that they are in a straight line.

Alignment gauge

see: wheel alignment

Alloy

A mixture of two or more elements.

Alloy wheel

A generic term used to describe any non-steel road wheel. The usual alloys are either aluminium or magnesium.

All Wheel Drive (A.W.D.)

A variation of four-wheel drive (4WD) designed to improve on-road traction in unfavourable road conditions or for ultra high performance driving. All-Wheel Drive (AWD) reduces wheel slippage and provides greater driver control over the vehicle. AWD usually does not require the driver to actively engage the system and does not have a low range. AWD automatically splits engine torque between the front and rear wheels as needed. All-Wheel Drive is generally an on-road system and is not designed for off-road use.

Alternator

A device which produces AC by converting the engine's (mechanical) energy into alternating electrical current at all engine speeds. The AC must be rectified (converted from AC to DC) by using diodes before reaching the vehicle's electrical system. The alternator is most commonly driven by a belt at the front of the engine. Alternators replaced the traditionally used direct-current (DC) generators and dynamos as they were less efficient especially at idle.

Ammeter

An electric instrument used to measure the rate of electrical current flow, measured in amperes.

Ampere

(A) A unit of measurement used in expressing the rate of electrical current flow in a circuit. It is determined by dividing the voltage by the resistance.

Ampere-hour

The measurement of the ability of a battery to deliver a stated amount of current for a stated period of time. The higher the ampere-hour rating, the more powerful the battery.

Anchor

  1. A mounting point on the vehicle frame, chassis or body for a non-structural but stressed component, such as a seat or seat belt.

  2. The stationary portion of a leading/trailing drum brake on which the heels of the brake shoes ride.

Ancillaries

The various components attached to the main part of the engine and driven by the engine itself -- such as the alternator, generator, power steering pump, supercharger, fuel pump, water pump, air conditioning etc.

Anemometer

Instrument for measuring the rate of airflow or motion.

Anneal

To remove hardness from metal by heating, usually to a red color, then allowing it to cool slowly.

Unlike steel, copper is annealed by heating, and then plunging it into cold water.

Annular

Something in the form of a ring.

Annular gear

A round gear with teeth cut on the outside for engagement with a pinion. Usually shrunk fit on to a mating diameter, e.g., starter ring on engine flywheel.

Annulus

A hollow gear which in the form of a ring with internal teeth.

See also: Epicyclic gearbox

Anodized

An electroplating process most commonly performed on aluminium parts, which forms a thin protective film on the surface of the metal. Anodizing is often accompanied by the use of a coloured dye, which gives a lustrous coloured finish to the aluminum parts.

Antechamber

A small auxiliary combustion-chamber, used in some compression-ignition engines, in which partial combustion of the fuel is used to force the burning mixture into the cylinder, promoting a more complete combustion.

Antifreeze

A chemical (usually ethylene glycol) added to the cooling system to prevent the coolant from freezing in extreme cold weather. It can also inhibits the formation of rust and other deposits which may clog the radiator and other cooling passageways.

Antifriction bearing

An anti-friction bearing is a bearing that contains moving elements to provide a low friction support surface for rotating or sliding surfaces.

Anti-friction metal

anti friction metal material used in bearings where the load is transmitted using no moving parts, by slide, without the aid of balls or bearings. Most commonly found in crankshaft shell bearings.

Anti-knock agent

A substance added to petrol to raise the octane number and reduce the gasoline's tendency to detonate, knock, or pink.

Anti-lock brake system

Anti-rattle spring

Disc brake systems have an Anti Rattle Spring in order to minimize the noise caused by contact between the brakes' friction element and the brake caliper or the piston cup.

Anti-roll bar

Also known as the anti-sway bar and stabiliser bar. It is usually a round bar which connects the left wheel suspension assembly with the right side. It can be found at the front and/or rear. Its main function is to keep both wheels rolling at the same rate when meeting bumps; but it also affects handling. A front anti-roll bar increases under-steer and a rear bar increases over-steer.

Antiseize compound

A paste that is applied to metal parts to keep them from sticking to other metal parts, particularly threaded surfaces such as spark plug threads, wheel studs, bolts and pins.

Anti-squeal shim

A shim (thin metal plate) placed behind the brake piston or the brake pad to reduce noise when the brakes are applied.

Anti-vibration mounting

The Engine, transmission, differential, and other components tend to vibrate when in motion, this increases noise and vibration at the points of contact with the frame members, which can cause wear and premature failure. Rubber blocks are used to cushion the vibration at the mounting points.

A-pillar

Looking at the side of a car, the pillar that is attached to the windscreen and supports the roof is called the A-post or A-pillar.

Aquaplaning

Also called hydroplaning. A dangerous tendency for a tyre to ride on a thin film of water, creating a loss of driver control until tyre contact with the road surface returns.

ARS (Air Ride Suspension)

A suspension system in which the load is supported on air-filled rubber bags rather than steel springs. An compressor fills reservoir tanks which supply air for the suspension (and the air brake system on heavy vehicles).

Articulated bus

A large public passenger bus, with two connected passenger compartments with an accordion-like section between them which flexes or bends to allow the bus to turn sharply around curves or corners as it bends at that part of the bus. Also called an accordion bus, bendy bus, banana bus, caterpillar bus, double bus, slinky bus, stretch bus, tandem bus, or wiggle bus.

Articulated truck

A large truck with two sections to give it a smaller turning radius.

Asbestos

A heat resistant and non-burning fibrous mineral widely that was widely used in the manufacture of brake shoes, clutch linings, etc. Asbestos is a hazardous material and the dust created by brake systems should never be inhaled or ingested as it can cause serious health issues.

Aspect ratio

The relationship in a tyre or wheel between the distance from the rim to the tread and the tire's width (i.e., ratio of section height to section width). For example, in a 205/80R17 tire, 80 is the aspect ratio, showing the height is 80% of the width. A lower aspect ratio describes a shorter, wider tire.

ASR

Anti-spin regulation. A Bosch term for traction control

Assisted brakes

See:

Asymmetrical power distribution

A system in a four-wheel vehicle where more power is transmitted to the front wheels than the rear wheels or more to the rear wheels than the front wheels.

Asymmetrical tread

The tread pattern on an asymmetric car tyre changes across the tread with different parts adapted for particular functions. The outside edge consists of large stiffer tread blocks which help with cornering. The inner tread blocks are smaller and designed to shift water and improve wet grip.

A.T.F.

see: Automatic Transmission Fluid

A.T.V.

Abbreviation of "All Terrain Vehicle". A vehicle that is designed to travel over all types of ground surface.

Automatic advance

A mechanism which adjusts the ignition advance by means of centrifugal weights or by a diaphragm controlled by intake manifold vacuum.

Automatic choke

A device attached to the carburetor that automatically reduces the amount of air (therefore enriching the fuel/air mixture) entering the carburetor by sensing changes in engine temperature.

Automatic four-wheel drive

A4WD is a driving system that automatically engages 4WD as required, usually by monitoring differences in individual wheel speeds, sensing tyre slip.

Automatic gearbox

See: Automatic Transmission

Automatic transaxle

An automatic transaxle combines the vehicle's automatic transmission and differential in one unit.

 

Automatic transmission

A drive-train mechanism which takes the power from the engine and transfers it to the driveshaft or wheels with a range of automatically selected gears, selected according to the varying road and load conditions as well as desired speed.

The automatic transmission does not use a traditional. Instead it uses a torque converter, which is a type of fluid coupling to transfer drive from the engine to the transmission. The gear ratios inside the transmission are achieved by a series of epicyclic gear set, with bands and clutches to achieve selections.

Automatic Transmission Fluid

ATF is a low viscosity fluid designed for automatic transmissions where it is required to transmit drive in the torque converted, hydraulically select gears and lubricate the moving parts. Poor transmission performance and gear selection can often be attributed to a low level or poor condition of the automatic transmission fluid.

Auxiliary brake light

Additional brake lights mounted at around eye level at the rear of a vehicle and designed to give a following vehicle more notice of your presence and intention of stopping.

Axle

An axle is a shaft on which the wheels rotate.

A full-floating axle is used to drive the rear wheels. It does not hold them on nor support them.

A semi-floating or one-quarter floating axle is used to drive the wheels, hold them on, and support them.

A three-quarter floating axle is used to drive the rear wheels as well as hold them on, but it does not support them.

A live axle holds the wheels and transmits power to the wheels. A dead axle or beam axle merely holds the wheels, but does not transmit power to the wheels.

Axle differential

In an axle, the differential allows the wheels to turn at different speeds with equal torque.

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