Automotive Glossary

Automotive words, phrases and abbreviations.

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S Classification (SAE)

Engine oil suitable for gasoline engines. The second letter in the classification denotes the quality and minimum conditions that the oil must meet.


Safe Weight Limit."


Society of automotive engineers. SAE International is the premier membership society dedicated to advancing mobility engineering worldwide. SAE is a global technology information and standards organisation.


Excessive flow on a vertical surface resulting in drips and other imperfections on the painted surface. Can Occur not only when the paint is wet, but also during baking in certain types of paints.


To smooth a surface with an abrasive paper or cloth.

Sandblasting (grit-blasting)

A method of cleaning metal, usually steel, by applying an abrasive with pressurised air. This is a very efficient method of removing paint and corrosion prior to repainting.


A power tool used with abrasives to roughen up or smooth surfaces quickly.

Sanding Block (Rubbing block)

A hard, flexible block to provide a smooth, consistent backing for abrasive papers used in hand sanding.

Sandscratch Swelling

Exaggerated distortion of sanding marks in the underlying surface, usually caused by solvents in the topcoat attacking the substrate.


Tracking in the topcoat of sanding marks in the substrate. Usually caused by either flatting with abrasives that are too coarse, or failure to adequately fill sanding scratches with primer fillers/surfacers


This can refer to any celestial body orbiting around a planet or star but usually means man-made equipment that orbits the Earth.


A surface finish that is approximately half-way between gloss and matt


A term referring to a colour's purity or richness. The more chroma in a colour, the more saturated that colour is.


Spark advance word output signal.



Scan Tool

Diagnostic tool that connects to an electronic control module on a vehicle to read fault codes and other data.


Diagnostic tool that connects to an electronic control module on a vehicle to read fault codes and other data. Some scanners can also connect to controller area networks (CAN).


To skim/scan text in order to get a general idea about it.

Scavenge Pump

The oil pump in the oil pan of a dry sump (oil pan) engine that returns the lubricating oil to a separate reservoir.


The process in the combustion chamber that clears the residual exhaust gases by the incoming air charge. The inlet and exhaust valves are both open for a very brief spell as the engine moves across top dead centre at the end of the exhaust stroke.

Schrader Valve

A spring loaded valve for retaining the pressure in a tyre and to allow for tyre inflation. Fitted into the rim of a wheel either as a separate valve for tubeless tyres or as part of the tube for tubed tyres.


Neuralgia of the hip and thigh.


Short for oscilloscope - Test equipment with a screen that can display electrical signals.

Scraper Ring

Piston ring that controls amount of oil on cylinder wall.

Screw Thread

A method of increasing force.

Scrub Radius

Effect on the tyre of steering turn.


A rubbing wear due to lack of lubrication or incorrect alignment. Examples are cylinder scoring and tyre tread wear on one side of a tyre only.


Oil, water or gas tight join.

Seal Land

The area on shafts that an oil seal lip seals against.


A liquid material that is used with or, in place of, a gasket to give a gas or liquid seal. Sealants can be either fully setting and go hard after application or non-setting which remain flexible in use. The correct type of sealant should be selected.


An undercoat that enhances adhesion by providing a barrier between the underlying paint and the new paint. Provides uniform colour holdout and an even, level surface for topcoat application.

Sealing Ring

A rubber (or similar material) ring that fits in or against an item to make an air or liquid tight seal.

Sealing Strip

Gasket to prevent leaks.

Search Engine

A program that enables you to locate information on the World Wide Web using keyword searches.


A machined face for making a good seal when matched with a valve.

Secondary Brake

Back up brake system, either mechanical or a split line hydraulic layout.

Secondary Cells

The cells of a rechargeable battery.

Secondary Shoe

Trailing shoe in a drum brake.

Secondary Winding

The high tension (secondary circuit) coil of wire in an ignition coil.


The development of tiny insoluble particles in paint (in the can) which results in a rough or gritty film.


Sequential Electronic Fuel Injection.

Seismic Mass

A small mass (weight) that moves to act as a sensing element.


Lock up of mechanical parts preventing or restricting proper movement.

Selector Clutch

Part of gear change system that automatically synchronises gear speeds before they are engaged.

Selector Fork

A fork that acts on, and moves a gear selector.

Selector Lever

Any lever to control a system that the driver uses to select a function.

Selector Mechanism

The mechanical connection between the driver and the gearbox shift hubs in a manual transmission.

Selector Shaft

Simple shafts that are attached to and move the selector forks, which in turn move the synchronisers.

Self Test

See Self-Test.


A mechanism or component that takes up free play automatically by either a mechanism or hydraulic pressure.


A system where the ECU can determine if an error has occurs in its own inputs, outputs or systems.


A system where the ECU can determine if an error has occurs in its own inputs, outputs or systems.

Self-Servo Action

Description of how the leading shoe on a drum brake system is pulled by the drum such as to increase its braking effect.


Start up and monitoring sequences for electronic control systems. Produce fault code data and triggers warning signals.

Semi Floating Axle

An axle hub arrangement with one bearing mounted inside the axle casing where it supports the axle shaft. The load is carried by the shaft which has shear and bending forces applied to it.


A material that can be made to conduct or block electricity. A diode is a good example.

Semi-elliptical Spring

A suspension leaf spring consisting of one or more leaves with mounting eyes or slippers at the ends and having a curved shape.


An intermediate gloss level between high and low gloss.

Semi-trailing Arm

A rear suspension type with a triangular trailing arm that has the chassis mounting points set at an angle to the transverse axis of the vehicle.


A material that can be made to conduct or block electricity. A diode is a good example.

Sender Unit

Another name for a sensor.


Electronic components that send electrical signals to the ECU.


Electronic components that send electrical signals to the ECU.


One thing that follows on to the next in time.

Sequential Fuel Injection

A petrol fuel injection system using ported injection timed in sequence with the engine firing order.

Sequential Injection

See Sequential Fuel Injection

Serial Fault Reader

Equipment that connects, usually to the OBD plug or similar, to read stored faults in an electronic system. See also scanner.

Series Circuit

Any electric circuit having all elements joined in a sequence such that the same current flows through them all.

Series hybrid

An engine drives a generator which in turn powers a motor that drives the vehicle.

Series Resistor

A resistor in a circuit that is connected in-line with the supply.

Serpentine Belt

A single flexible drive belt that provides a drive from the engine crankshaft to all ancillary components. Replaces a series of individual belts.


A servo mechanism (informal)

Servo Cylinder

Ram cylinder that supplements physical forces in operating a control (as for example steering, a brake or clutch), either by direct mechanical amplification or by external power assistance.


System or device that supplements physical forces in operating a control (as for example a brake or clutch), either by direct mechanical amplification or by external power assistance.


A motor that supplements physical forces in operating a control.


Service Engine Soon (light)


Gravity separation of one or more components from a paint and the resulting layer of material on the bottom of a container.


Sequential Fuel Injection


Part of a leaf spring suspension system that allows movement (swinging shackle) or is fixed to the chassis (fixed shackle).

Shackle (Slipper)

Allows for changes in length between the ends of a leaf spring as suspension moves.


Variation of a colour. A colour that is basically blue can have a red shade or yellow shade as well as being blue. Shade is also called tone or undertone, since it describes the subtle tone of a colour.


A cleansing agent consisting of soaps or detergents used for washing the hair – or a car!


The gloss or flatness of a film when viewed at a low angle.

Sheer Force

A force that tends to sheer or cut something much like the action of scissors.

Sheet Moulded Compound

Fibreglass or thermoplastic plastic material moulded to shape and used as an outer panel on a vehicle.

Shell Bearings

Plain bearing formed from two interlocking and abutting thin walled semi-circular cups.

Shift Fork

A fork that acts on, and moves a gear selector.

Shift Ring

Part of a gear selector mechanism.

Shift Rod

A simple rod that connects the gear change lever to the gearbox.

Shift Shaft

A shaft that is used as part of a gearshift / gear changing mechanism.

Shift Timing

The point at which an automatic gearbox changes gear.


A thin metal sheet or washer used between two components to adjust free play. Shim material is produced in standard sizes.


Side to side movement of the wheels that causes the tyres to lose some grip on the road.

Shock Absorber

Method of dampening suspension spring shock oscillation. Damper.

Short Circuit

A short circuit is one that allows a current to travel along a different path from the one originally intended.

Short Engine

Engine block containing crankshaft and pistons. Usually referred to when being replaced to overhaul the engine.

Short Motor

The engine block and crankcase together with all internal running components, pistons, crankshaft, etc.

Shrink Fit

An interference fit obtained by heating the outer component or cooling the inner component so that they can be assembled with a push fit. When the temperatures are balanced the parts retain their interference fit.


Loss of solvent during the drying/curing process of a paint film.


General term used to describe a cover.

Shunt (Electrical)

A parallel part of an electrical circuit. An example is the shunt windings of some starter motors.

Side Draft

A carburettor where the choke tube (venturi) is fitted horizontally.

Side Thrust

Forces caused by cornering.

Side-draught Booth

A spray booth in which air movement is from the front to back.


Viewing the repaired area from an angle just past the reflection of the light source.


Siemens IT solutions and Services Ltd – Service provider for MOT Computerisation.

Significant Figures

The number of digits expressed in a measurement. Sig. fig. can appear before and/ or after the decimal point.

Signposting Guidance

within the specifications for the new AS levels A levels and GNVQs, opportunities for developing or producing evidence for assessment of key skills.

Silencer (Muffler)

A component in the exhaust system to absorb the gas shock waves and noise in order to reduce the emitted noise from a vehicle engine. Also known as a muffler.(US term).


One of many polymeric organic compounds of silicone with high resistance to cold, heat, water and passage of electricity.


A chemical compound with excellent water repellency and a slippery feel. Silicones are commonly used in automotive waxes to enhance application and ease of removal, and to increase gloss and durability. The term 'Silicones' is often applied to the defect known as 'cratering' or 'fish-eyes'

Simple Gear Train

Two or more gears in direct mesh.


Simulation is the imitation of some real thing, state of affairs, or process. The act of simulating something generally involves representing certain key characteristics or behaviours of a selected physical or abstract system.


Activities that simulate or model reality.


Two or more things happening at the same time.

Sine Wave

The wave pattern of an AC current. The positive and negative patterns are an inverse copy of each other.

Single Point Injection

A petrol fuel injection system using a single point injector in a throttle body in the inlet air supply and positioned on top of the inlet manifold. Also throttle body injection (TBI)."


A condition in which the topcoat appears to sink into the primer coat causing a loss of gloss. Also, a loss of gloss due to improper solvent selection.


A manufacturing process using heat and pressure to form metal and composite components. Examples are brake lining materials and some components traditionally produced by forging or hot stamping.


Very narrow groove or cut in the tyre tread that aids the dispersal of surface water between the tyre and road.


Side Impact Protection System


Special test track for skidding on!


To skim/scan text in order to get a general idea about it.


The formation of a thin, tough film on the surface of a liquid paint film, usually due to oxidation, hardening, or drying of the paint.

SLA Suspension

Short and long transverse suspension arms. The upper arm is the shorter of the two. The geometry of this layout keeps the wheel camber reasonably constant during suspension movements. Also known as 'unequal wishbones'.

Slave Cylinder

A hydraulic cylinder receiving a force and operating a mechanism. Examples are the clutch cylinder and the brake or wheel cylinders in brake units.

Sleeve (Cylinder)

A steel sleeve used to form a running surface for pistons in an engine. Also known as a cylinder liner.

Sliding Caliper

A brake caliper that has one piston and one sliding section.

Sliding Joint

A drive shaft joint with the ability to change length and to transmit movement usually with a splined construction.

Sliding Resistance

The frictional value for the surface of a sliding component in contact with the track or road on which it runs. An example is the sliding resistance of a road tyre skidding on a road surface. The sliding resistance is usually less than the rolling resistance.


(1) A plate fitted on a rotating shaft in front of an oil seal to reduce the volume and pressure of the oil on the seal. (2) A plate or protuberance on a crankshaft for throwing oil onto the cylinder walls or other components.


Loss of grip between two frictional faces.

Slip Angle

The difference between the true line and the actual line of a vehicle wheel when cornering.

Slip Ring

Continuous ring of copper used with a brush to transmit electricity through a rotating component.

Sludge (Oil)

Lubrication oil deterioration where the oil thickens, mixes with contaminants and forms a thick and glutinous jelly or paste.


Description of what happens to oil if it is not changed as recommended - a sludge forms that looks like Mississippi mud!

Smart Card

A card issue to an authorised user to access the MOT database via the VTS Device.

Smoke Meter

Opacity meter used to measure the amount of smoke in diesel engine exhaust gases.


Special Notice – an official notice issued from time to time by VOSA to inform AEs, NTs and other system users of changes to the testing scheme. SNs may also be used to highlight areas of concern and to advise of developments of the scheme.

Snail Cam

A cam that is shaped like a snail shell. In other words it has more effect the further it is turned.


Term used to describe the action of a clutch when the take up is too sharp/severe.


State of charge (of a battery)

Sodium Hydroxide

A chemical used as the inflater for some air bags.

Soft Interface Pad

A support pad to which a finishing film abrasive disc can be attached. A soft interface pad reduces the pressure transmitted to the surface to be finished and moderates the cutting effect of the abrasive. Also used to great advantage on highly contoured surfaces.

Soft Jawed Vice

A vice with soft material fitted to the jaws to prevent damage to any components held in it.


A computer program.


Single Overhead Camshaft Engine.


A mixture of lead and tin used to join wires and terminals.

Soldered Joint

Termination of cables with solder.


A coil of wire. Usually used to refer to a device containing an electromagnet.

Solenoid Switch

Electro-magnetically activated electrical switch.

Solenoid Valve

A valve operated by a solenoid. Fuel injectors are good examples.


The part of the paint that does not evaporate but stays on the surface to form a film. Usually measured on a weight or volume basis.


Homogeneous liquid or mixture of two or more chemical substances.


The ability of a liquid to dissolve a solid. Measured by the viscosity of a solution at a certain concentration of solid resin. The same solvent may have different solvency for different resins.


A liquid which will dissolve another material, usually resins or other binder components. Commonly organic liquids.

Solvent Density

The weight per unit volume of a solvent or solvent mixture.


The particular mixture of liquids (usually true solvents and diluents) that give a paint the desired flow or evaporation properties.


Describes a paint which contains organic solvents rather than water as its primary liquid component.


Bumps or small craters that form on the paint film, which are caused by trapped solvent trying to escape through the drying paint.

South Pole

The term used to describe one of the poles of a magnet where the magnetic field lines of force end.


A metal sheet or washer used between two components to adjust free play.

Spade Terminal

A flat blade terminal used to make an electrical connection.

Spark Ignition (SI)

The ignition of petrol by a spark in the combustion chamber of an engine.

Spark Plugs

Used to provide a small gap in the combustion chamber of an engine, for a spark to jump across.


Device that converts audio signals to sounds that humans can hear.

Specific Gravity

The ratio of the density of a substance to that of water.

Spell Checker

Most computer applications (i.e., Microsoft Word, Excel etc.) will enable you to check documents for incorrect spelling.


To form a word with a series of letters.


Single point injection. Electronic throttle body fuel injection system.


1. Arachnid with eight legs...2. Name sometimes used for the shaft on which planet gears rotate in a differential.

Spider Diagrams

A series of lines and boxes containing relevant information. A form of note taking.


A bearing between two shafts mounted end to end axially.

Spigot Bearing

Bearing for a spigot shaft. Usually used to refer to the bearing inside the end of the crankshaft, into which the gearbox input shaft fits.


A rotating shaft.

Spindle Arm

(1) Lever that imparts the steering action to the steering knuckle or stub axle assembly, as from a tie rod or track rod. Also steering arm, though this term is often used for the lever that imparts steering action from drag link to steering knuckle. (2) An intermediate arm in a steering system.

Spindle Bushes

Simple bearings on which a spindle rotates.

Spiral spring

These are generally made of rectangular section material, flat strip, with round edges. They are general used as brush springs in D.C. motors. Also known as clock springs

Spirit Level

A device full of liquid with a bubble that moves to the centre when it is level.


A joint in two or more cables made by crimping or soldering the cables together.


Axial groove on a shaft and hub.

Splined Joint

A toothed joint between two shafts that will transmit rotation but also allow axial (back and forth) movement.


Axial grooves on a shaft and hub.

Split Pin

A soft steel pin that has two sides that are folded out to secure the pin in a hole. Sometimes called a cotter pin.

Split Rings

Two continuous rings of copper used with brushes to transmit electricity through to a rotating component such as an alternator rotor field winding.

Split Slip Ring

Two continuous rings of copper used with brushes to transmit electricity through to a rotating component such as an alternator rotor field winding.


Tool used to split ball joints or track rod ends from the steering arms.


Thin metal rods that join the wheel hub to the rim and support the weight of a vehicle.

Spongy (Brakes)

Usually caused by air in the hydraulic brake lines. A soft and imprecise feel to the brake pedal.

Spot Repair

A type of refinish job in which a section of the vehicle smaller than a panel is refinished. The paint is usually blended into the surrounding area.


Spark output Signal.

Sprag Clutch

A uni-directional rotary clutch that uses a series of shaped (like a figure 8) rollers and springs to either freewheel or grip the outer tracks to transmit a rotating force.

Spray Booth

An enclosure used to paint vehicles. Spray booths have controlled air flow and normally have temperature control or baking capacity.

Spray Gun

A device that mixes paint and compressed air to atomise and control the spray pattern as the paint leaves the fluid needle and air cap.


Paint is atomised in a spray gun and the stream of atomised paint is directed at the part to be painted. Atomisation is normally achieved using high pressure air, by high fluid pressure, or by electrical means as in an electrostatic process.

Spreader Valve

The adjustment valve on a compressed air spray gun which directs an air stream against the sides of an atomised paint cloud to adjust the spray pattern.


A computer program often used to create financial forecasting documents.

Spring Clip

Small fixing device that can usually be removed by hand.

Spring Eye

A hole formed at the ends of leaf springs to allow fixing to the chassis.

Spring Ring

Small spring fixing device like a circlip.


Gear wheels usually used to drive or be driven by a chain.

Sprung Mass (Weight)

The part of the vehicle supported by the suspension springs.

Spur Gear

A gear wheel with straight cut teeth.

Spurious Data

Data that falls outside what is expected.

Square Metre

The area enclosed by a square with sides of 1 metre long.

Square Wave

The wave pattern formed by a digital signal.


High pitched noise (screech) from friction components. Examples are brakes, clutch and drive belts.


A flexible rubber blade used to wipe off excess water from washed or wet sanded areas.


A twisting or side-to-side movement.


Service Reminder Indicator.


Supplementary Restraint System.


System Readiness Test


Speed Sensor


Solid State Ignition

Stabiliser Bar

A torsion bar that connects the suspension on each side of a vehicle's axle to transmit movement from one side to the other in order to reduce vehicle roll when cornering.


An additive included in a paint mixture to prevent degradation during storage.

Stall Speed

The maximum engine speed (rpm) of a vehicle with automatic transmission that can be obtained at full throttle against the brakes without moving the vehicle. A test procedure to check the torque converter.


When an engine stops because it is running too slowly or due to some other influence such as a learner driver!


A manufacturing process using punches and dies to cut objects out of sheet materials.

Standard Form

Used so that very large or very small numbers can be written in a more convenient way.

Standards moderation

The means by which awarding bodies ensure consistency across centres and ensure that national standards are being maintained and applied.

Star Wound Stator

An alternator stator winding with the three-phase coils connected at the centre in order to give a large voltage output. The normal winding for light vehicle applications. Also 'Y' type stator.

Starter Motor

A powerful electric motor that produces high torque to rotate the engine for starting.

Starter Solenoid Feed

Small wire that causes the solenoid to operate. Feed is from the starter switch and usually a relay.

Starter Switch

The switch that operates the starter motor. Usually part of the ignition switch.


A term that indicates components that are stationary. The opposite of dynamic when the components are in motion.

Static Balance

The balance of a rotating component about the rotational axis. Wheel balance has both static and dynamic quantities.


Numerical data.


Stationary part of machine. Examples are the magnetic inductance component of an alternator and the reaction member in a torque converter.

Stator Windings

Electrical windings on the stator of an alternator.


Self-Test Connector.


A ferrous metal commonly used as a substrate for paint, which must be painted to prevent corrosion.


Mechanism or means whereby the direction of a vehicle is controlled.

Steering Arm

(1) Lever that imparts the steering action to the steering knuckle or stub axle assembly, as from a tie rod or track rod. Also spindle arm (US), though this term is often used for the lever that imparts steering action from drag link to steering knuckle. (2) An intermediate arm in a steering system.

Steering Axis

The point about which the steered wheel turns.

Steering Column

The linkage and outer housing between the steering wheel and the steering gearbox/rack.

Steering Gear

Small pinion that operates the steering rack. OR Worm gear that operates a steering arm.

Steering Gearbox

Gearcase in which the rotary movement of the steering column is converted into angular motion of the drop arm or pitman arm.

Steering Geometry

(1) Position of the wheel and steering swivel mountings. (2) Combination of angles in steering swivel.

Steering Nut

Part of a steering gearbox that moves on the worm gear.

Steering Rack

System where a small pinion works on a flat gear (rack) to move the steering arms.

Steering Shaft

The shaft that rotates as the steering wheel rotates.

Steering Swivel

The turning component that carries the steered wheel, king pin, stub axle assembly and McPherson strut.


Hard and temperature resistant metal alloy used to coat exhaust valves.

Stepper Motor

An electrically controlled motor that gives precise incremental movements.

Stepper Motors

An electrically controlled motor that gives precise incremental movements.


Short Term Fuel Trim


Self-Test Input.


Self-Test Output.

Stoichiometric Ratio

The chemically correct ratio for air and petrol to achieve complete combustion. An air/fuel ratio of 14.7:1.

Straight Line Sander

Sander that uses a back-and-forth movement to sand a surface using sandpaper on its shoe.


Strain is the amount of extension in size divided by the original length.


A mesh filter for basic cleaning of oil or fuel. Usually fitted in the oil pan or fuel tank.


Alternative term for a choke flap in a cold start device for a carburettor.

Strap Wrench

A tool used to undo filters. A simple strap tightens around the filter to grip it securely.

Strap Wrenches

See Strap Wrench.


To form, arrange, or deposit in layers. This usually refers to the fuel air charge in a cylinder where the layer next to the spark plug is richer than the layers further away. used for lean burn applications.

Strength (of a pigment)

The opacity and/or tinting power of the pigment. The measure of the ability of a pigment to hide or provide colour to a substrate.


Stress is a measure of a force or load divided by the cross-sectional area of a material to which the force is applied (N/m2).

Striker Pin

Part of the door latch mechanism.

Strippable Coating

Also called booth coating. A sprayed peelable film which is applied to the internal walls of spray booths to provide protection from overspray. When the coating becomes sufficiently contaminated, it is easily peeled or scraped away and replaced by a new layer of strippable material.


A flashing light. A strobe light is used to check and adjust ignition timing.

Stroke (Cylinder)

The length of travel of the piston in the cylinder. Twice the throw of the crankshaft.


Term used to describe a suspension unit that operates telescopically.

Stub Axle

Alternative name for a king pin assembly or steering swivel.

Stub Axle Assembly

Alternative name for a king pin assembly or steering swivel.


Threaded rod.


A low cost, colourless monomer which polymerizes readily. Widely used in the manufacture of fibreglass mouldings, plastic articles and polyester finishes.


An extra chassis component used to support a major part such as the engine or transmission.


The object or material to be painted. It may be bare metal, an old paint finish, or a foundation coating applied as part of a refinishing procedure.

Suction-feed Gun

A spray gun that has the paint container connected directly below it. Air flowing across the air cap creates a vacuum and, thus, draws the paint up from the container via a metal tube.


Lower part of an engine or gearbox usually containing lubrication oil.

Sun Wheel

Central gear wheel of an epicyclic gear train or differential.


A fixed or operable (venting or sliding) opening in an automobile roof which allows light and/or fresh air to enter the passenger compartment. Sunroofs may be manually operated or motor driven, and are available in many shapes, sizes and styles.


A mechanical air pump driven from the crankshaft and used to boost the intake air charge for an engine.


To direct, manage, or oversee; to be in charge.

Supplied-Air Respirator

A respirator that provides safe breathing air to a painter while working with paints. The air supply provides not only breathing air but positive pressure on the edges of the mask to eliminate any contaminants from the outside air.


An electrical device fitted in parallel with a circuit to reduce the emission of electromagnetic waves at radio frequencies.

Surface plate

A flat metal plate for gauging the accuracy of a plane surface in precision metalworking


A heavily-pigmented foundation coating designed to be applied to a substrate for the purpose of smoothing or uniforming the surface for the subsequent coats of paint. Usually sanding is required, although non-sand variations are available.


Means whereby vehicle body is supported on its undercarriage, comprising springs, dampers and locating linkages.

Suspension Arms

Linkages used to construct a suspension system.


Service connector for octane and idle speed adjustment.


Small pieces of metal that are produced during machining.

Swash-plate Compressor

See swash-plate pump.

Swash-plate Pump

A type of pump that uses a rotating plate, that is radially off-set from the axis of the shaft, to operate the pump pistons in their cylinders. This design can also be used for compressors.


Short Wheel-Base

Swept Volume

The volume inside a cylinder above the piston crown at bottom dead centre minus the volume above the piston at top dead centre which forms the combustion chamber and is given the term 'clearance volume'.

Swinging caliper

A type of floating caliper with wedge-shaped disc pads (only one of which is activated by hydraulic pressure from the piston, the other being fixed), which can pivot on its hinge pin to equalize the pressure on both pads

Swirl Marks

A pattern of small scratches left in a finished surface by the wheel of a buffer or sander during the sanding and/or compounding operation, or by hand flatting using a circular motion.

Switch Pack

General term to describe a collection of switches in one unit, window lift switches in the driver's door for example.

Swivel Axis

Line about which the steering turns.

Swivel Joints

Joints used as part of a steering linkage about which the steering turns.

Swivel Pins

Pins used as part of a steering linkage. Often called Kingpins.


A description of objects that are the same on each side of their centre line.


The observed or measures result of a fault in a system.

Synchromesh Gear

Gear change system in which the speed of rotation of a selected gear is automatically synchronized with that of the mainshaft.

Synchromesh Hub

Cone clutches that are part of a gear change system which equalises the speed of a rotating gear.


Two or more occurrences happening or being made to happen at the same time.


Part of gear change system that automatically synchronises gear speeds before they are engaged.


An adjustment that causes something to occur or recur in unison.


Part of gear change system that automatically synchronizes gear speeds before they are engaged.


Prepared or made artificially, in contrast to naturally. For example, synthetic engine oil is NOT made from crude oil!

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