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Glossary Of Terms

ABS - anti-lock braking system, and sometimes referred to as an anti-skid braking system.

ABS prevents wheels from locking up under braking by sensing wheel slip and releasing and reapplying brake pressure, even when the foot remains firmly planted on the brake pedal.

The system maintains steering control, even under maximum braking.

See also sensors.

Aquaplaning - describes the situation where a tyre loses its grip on a wet surface and "skates", greatly reducing a driver's control.

Adaptive shift automatic transmission - an extension of conventional autos whereby an electronic system will allow different shift points.

The computer can alter the shift points according to the driver's style (use of the accelerator) and the prevailing road conditions.

Sometimes referred to a "fuzzy logic".

Airbag - a bag designed to inflate instantly in the event of a collision to prevent occupants from hitting the dashboard, steering wheel or other parts of the vehicle.

Side airbags, some of which are designed to protect the head and the chest, head airbags and curtain (window) airbags are becoming increasingly common.

Airdam - reduces the amount of air forced underneath the car at higher speeds (and therefore lift) by redirecting it around the car.

It is usually integrated with the front bumper and incorporates air ducts to cool the engine bay and slots to cool the brakes.

Spoilers, on the other hand, direct air over the car to generate downforce, the opposite of lift.

High downforce and reduced aerodynamic lift will improve the car's handling characteristics.

Approach angle - the angle a 4WD can take a steep climb or descent without scraping the front on the ground.

Departure angle is the angle the rear of a 4WD can take a climb or descent without scraping on the ground.

Ramp-over angle is the angle a 4WD can drive over a mound without scraping underneath.

Bash plate - fitted underneath vital components like the engine, transmission and fuel tank.

Usually made of thick steel and designed to take hard knocks off-road.

Bench seat - a one-piece full-width seat, found in most cars across the rear seat but also available (usually as an option) in the front on some vehicles.

Bore - the width of the engine's cylinders.

Stroke is the distance the piston travels as it rises or falls in the cylinder.

If the bore is greater than the stroke it is often described as "oversquare" (if the measurements are the same, they're termed "square") and usually points to a higher performance engine.

Undersquare is the opposite, and usually better for fuel consumption and low-speed work like towing.

Braking distance - the distance in which a vehicle stops from a given speed once the brakes have been applied.

Bullbar - a one-piece tubular bar to protect headlights, radiator and front panels from damage caused by hitting wildlife.

A nudge bar is primarily designed to protect the radiator in a low-speed collision.

Cabriolet - another name for a convertible, which refers to a car (usually a coupe, or two-door car) with a removable or foldable roof.

Cd - co-efficient of drag, a measure of how easily the car moves through the air without causing undue drag or resistance.

Column stalk - a lever attached to the steering column which, with the help of another stalk on the opposite side, controls such items as the indicators, windscreen wipers, headlights, dip-beam and flasher.

Convex exterior mirror - a lens fitted on the left-hand exterior mirror on some cars, which provides a wider view for the driver.

CVT - refers to a continuously variable (automatic) transmission that uses drive belts to transmit torque and allows for various ("stepless") ratios.

Disc brakes - unlike drum brakes, where expanding shoes make contact with drums and the resulting friction slows the car, disc brakes use a calliper that grips the disc rotor to the wheel to gain friction.

They tend to create more heat than drum brakes, but is designed to continue operating effectively in these conditions.

Ventilated discs, often seen on sports cars, use two rotors sandwiched together with cooling space in between.

DOHC - refer to twin cam.

Drivetrain - a collection of components necessary to transmit torque from the engine to the wheels to get the car moving.

It encompasses the engine, transmission, clutch (on manuals) torque converter (automatics) and driveshafts.

If the torque is transmitted to the front, it's described as front-wheel drive.

To the rear - rear-wheel drive.

In front-wheel drive cars the gearbox and differential are one unit called a transaxle.

In rear-wheel drive cars the power has to be transmitted to the driving wheels from the engine at the front down the length of the car to the differential.

Four-wheel drives can have the differential located at both the front and rear.

Drum brakes - these are almost always found on the rear wheels and are generally regarded as inferior to disc brakes because heat cannot escape as effectively and heavy braking can cause the drums to quickly "fade".

Electronic brake distribution - is an additional feature of more sophisticated ABS braking systems, where an electronic control system measures such parameters as road speed to distribute braking force more effectively.

Engine capacity - the volume swept by all the pistons of an engine, within their bores, from the top to the bottom of their travel.

Measured in litres, cubic centimetres (cc) or, primarily in the US, in cubic inches (cu.


Estate - a station wagon.

Exhaust gases - the gases formed by the combustion of fuel and emitted by the exhaust system.

They include water vapour, carbon dioxide, carbon monoxide, oxides of nitrogen and unburnt hydrocarbons.

Foglamp - an auxiliary headlamp mounted low on the front of a car (often on the bumper) for use in fog.

Casts a broad, flat beam on the left-hand kerb.

Four-wheel drive - available on an increasing number of passenger cars as well as the traditional off-roaders, the chief advantage of 4WD is added traction (grip) on slippery surfaces.

Disadvantages include higher purchase price, increased weight (and consequently higher fuel consumption) and higher repair costs.

Four-wheel drive systems - there are a number of 4WD systems, generally split between full-time and part-time operation.

As the names imply, power is sent to all four wheels either all the time or some of the time.

Full-time 4WDs can be driven on all road surfaces.

Some full-time systems are "selectable", running in two-wheel drive when the driver so chooses.

Part-time systems run as two-wheel drive until the driver selects four-wheel drive for off-road use.

On-demand part-time systems automatically transfer power to the rear wheels on all surfaces when slip is detected.

Fuel filler cap - the lid of the petrol tank.

Fuel injection - this system of sending fuel to the engine combustion chamber is more efficient than the outdated carburettor, bringing better fuel economy and less emissions.

Multipoint fuel injection provides improved performance.

Halogen headlamps - give a whiter, brighter light than the commonly used incandescent bulbs.

Some manufacturers now offer xenon headlamps, also for improved lighting.

Hard top - refers to the rigid roof attached to a sportscar or recreational body.

It can be part of the body structure or it can be fitted as an alternative to a soft top or fabric roof.

Headroom - often used as a general term by road testers, however is also refers to a measurement from the seat base to the roof headlining.

Other measurements include shoulder room, the internal width of the car from one internal door panels to the opposite panel, and legroom, taken from the edge of the seat base to either the firewall (front) or to the front seatback (rear) when fully forward.

Inline engine - engine configuration in which all the cylinders are arranged in a single line, with their axes parallel.

A "V" engine has two banks of cylinders in a V-configuration.

Kerb weight - or kerb mass, is the overall weight of the car, unladen and with half a tank of fuel.

Limited slip differential (LSD) - a mechanical version of traction control, limiting wheel spin on an axle in two and four-wheel drives.

Litres per 100 kilometres - measurement of the fuel consumption of a vehicle.

Unlike miles per gallon, the smaller the figure the less fuel consumed.

Lockup torque converter - primarily a fuel-saving device on an automatic transmission where there's no loss of power - a common trait of autos.

Basically, the input shaft for the transmission turns at the same speed as the engine's crankshaft, so there's no loss of mechanical efficiency.

Low profile tyres - have excellent grip on dry roads but are stiffer than ordinary tyres and therefore provide a firmer ride. "Profile" refers to the height of the sidewall compared with the width of the tread, expressed as a percentage.

A number of 60 or lower is considered low profile.

Low-range reduction - an extra set of gears for slow-speed off-road driving (usually only the lowest two ratios are required).

High range refers to the normal set of gears used for driving at normal road speeds.

MacPherson struts - a modern front suspension system which supports the car's weight and acts as shock absorbers.

The main alternative is a double wishbone arrangement.

Metallic paint - where aluminium flakes are embedded into the paint, improving the car's finish and reflectiveness.

Monocoque - the most common form of chassis construction for passenger cars and, increasingly, four-wheel drives.

Unlike a ladder frame, where the chassis and body are separate for high strength, monococques are specifically designed to crumple in the event of a collision and absorb energy, protecting the occupants from the full force of the crash.

Negative camber - inward tilt sometimes given to the front or rear wheels of vehicles with independent suspension, to increase the cornering power of the tyres at speed.

Neutral handling - means the car doesn't show much understeer or oversteer.

Normally aspirated - an engine which is not turbocharged or supercharged.

NVH - noise, vibration and harshness, a term used to describe all the rattles and squeaks sometimes encountered in new cars.

Odometer - instrument for recording distance covered.

Usually incorporated within the speedo arc and records kilometres and sometimes tenths of a kilometre.

Overdrive - a fuel-saving device, overdrive is an extra gear on a manual or automatic which makes the engine turn more slowly at higher road speeds.

It's called overdrive because the driveshafts are turning faster than the engine.

Oversteer - this refers to the car's tendency to lose rear wheel grip, with the back end sliding out.

Oversteer is prevalent in most rear-wheel drive cars when pushed.

Performance - how well any car - not simply "performance cars" - accelerates and stops, but sometimes used to describe how well it handles as well.

Pillar - upright body section supporting the roof.

Front pillar is called A pillar, middle B and rear C pillar.

Most wagons have a D pillar as well.

Power - a figure pointing to the maximum number of kilowatts (the metric equivalent of horsepower) an engine can achieve and the corresponding engine speed (rpm).

Revolutions per minute (rpm) - this is displayed on a tachometer in the instrument panel and refers to how engine speed is measured.

The redline on the tachometer shows the maximum rpm; upon reaching redline, the driver will be forced to select a higher gear if a rev limiter is fitted.

Ride - like handling, ride is typically a subjective notion of the car's level of comfort (handling generally refers to the car's dynamic cornering ability).

Manufacturers must strike a balance between ride and handling, bump absorption and stability.

An ultra-soft ride can aggravate body movement during directional changes (bodyroll) and reduce steering response.

Rubbing strips - rubber strips running down the length of the car and on bumpers as the first line of defence against wayward shopping trolleys and carelessness from occupants in the vehicle parked next to yours.

Saloon - a sedan.

Sat-nav - an abbreviation for satellite navigation, increasingly common these days.

Provides a television readout of the exact location and voice commands along the way to the required destination.

Seatbelts - are usually "lap-sash" (or three-point) restraints which run diagonally from the shoulder to the hip as well as across the lap.

Lap-only belts are today regarded as inadequate, though are commonly found in the centre-rear position of many budget cars, as well as some luxury European cars.

Pretensioners tighten during an accident to give added protection.

Adjustable anchors alter the height of the shoulder strap to improve belt fit, and are especially helpful for smaller people.

Sequential shift - often described as a "Tiptronic-style" automatic, after Porsche's pioneering system.

It is simply an automatic transmission that gives the driver the ability, if desired, to move up and down through each gear sequentially.

It is not a euphemism for a clutchless manual, which dispenses with a clutch pedal (the clutch is controlled electronically) but in most other respects it operates as a manual transmission.

Sensors - these are linked to the anti-lock brake system and are used to monitor wheel rotation.

There is usually one sensor per wheel.

Hydraulic pressure channels are also used on at least two wheels (four is the optimum) to relieve pressure on wheel/s that would otherwise lock up.

Side cladding - usually found on four-wheel drives, it refers to plastic panels usually linking the front and rear bumpers to add an element of ruggedness to the car's appearance as well as protect the paintwork from rocks and shrubs etc.

Springs - an essential component of any suspension system because they absorb bumps.

Dampers (or shock absorbers) absorb the re-bound movement of the spring.

Without dampers, the vehicle would bounce along the road and create havoc for the driver.

Steering - can be powered by an engine-driven hydraulic pump and varied according to engine speed or the actual road speed.

There are two basic steering systems, the common rack-and-pinion set-up and the ageing recirculating ball system.

Steering feedback - indication, passed back through the steering system to the drivers hand, of where the front wheels are pointing or how much grip their tyres have.

SRS - Supplementary Restraint System (see airbag).

Suspension - there are two basic types of suspension systems, rigid (or solid) axle and independent.

Rigid axles, where a solid beam runs from across from one wheel to its opposite number, can be either "live" (where the wheels are driven) or "dead" (wheels are not driven).

As the name suggests, independent suspension allows a wheel to ride over bumps without affecting the other.

Most modern cars have independent front suspension, however some manufacturers of rear-drive cars still persist with a live rear axle instead of independent rear suspension (or IRS).

Switchgear - refers to the set of switches and dials, etc.

that used to operate the minor functions of the vehicle such as HVAC (heating, ventilation and air-conditioning), stereo, headlights, cruise control and indicators.

Tachometer - also referred to as a rev-counter, although this colloquial term is inaccurate; the instrument records the rate at which the crankshaft is rotating (revolutions per minute, or rpm), not the number of times it does so.

Tonneau - a waterproof fabric cover that fits over the passenger compartment of a convertible.

Torque - also known as pulling power, or what the sense of purpose (commonly referred to as grunt) you feel when you press the accelerator pedal.

It is measured in Newton metres and is an extremely important figure when considering a car's response in normal driving and under higher loads, such as when towing.

A low peak torque figure (rpm) will point to better acceleration will be when cruising along in higher gears or when pushing off from low speeds.

However, high torque at high engine speeds is often seen on performance cars.

Torsional rigidity - refers to the vehicle's ability to resist twisting forces which, particularly during cornering, braking and acceleration, attempt to bend the vehicle from the front right to left rear or front left to right rear.

This form of rigidity plays an important role in areas such as ride, handling and structural integrity.

Track - the distance between the centre of either the two front or rear wheels, measured from the middle of the tyre on one side to the middle of the tyre on the other side.

Hence, "front track" or "rear track".

Other measurements include overall height, the height of the car and not including roofrails if fitted, overall length front to rear and overall width, which usually does not include the exterior mirrors.

Traction control - a system that uses ABS to apply braking force to a slipping wheel.

Drive can be directed to the wheels with the most traction.

Transfer case - found on most "serious" four-wheel drives, this is part of the transmission which channels drive to front and rear axles and may contain the gearset for low range.

Transverse engine - where the engine is placed across the car in an east-west position, instead of lengthwise.

Two plus Two (or 2 + 2) - usually a sports car and often a convertible, this refers to a four-seater.

Turbocharger - a small compressor driven by the engine's exhaust gases which increases power.

A supercharger is driven by a belt off the engine to increase power.

An alternative to both is the use of a multivalve engine, where more valves than the traditional two per cylinder move air and fuel through the engine more quickly.

That said, some cars have multivalves AND turbochargers.

Turning circle - a good measure of how easy the car will be to park or U-turn.

Usually measured kerb to kerb using the front outside tyre, though sometimes measured "wall to wall" using the outermost extremity of the car as it corners.

Sometimes only the radius is given - for the diameter, or complete circle, multiply the radius by two.

Twin cam (DOHC) - also known as DOHC (double overhead camshaft), twin cam refers to an engine that has two camshafts per cylinder bank.

Having one camshaft responsible for intake valves and another for exhaust valves is more efficient than one cam for both intake and exhaust.

The system typically provides better fuel efficiency and performance.

Understeer - often described as front-end push, understeer occurs when the car resists turning into a corner and wants to steer straight ahead.

Most cars are designed to understeer because more drivers will be comfortable with this type of handling rather than oversteer.

Viscous coupling - a common four-wheel drive system where an enclosed tube connected between transfer case and driveshaft contains viscous fluid which heats up when a pair of wheels start to spin and 'locks' the driveshaft, giving 4WD.

Water-cooled engine - engine in which water heat is transferred to circulating water rather than directly to air blowing over cylinder heads.

An air-cooled engine is cooled directly by air, which is blown (usually by a fan) over the finned cylinder barrels and cylinder heads.

Wheel articulation - lateral movement of a live axle.

For independent suspension this is described as wheel travel.

Wheelbase - the distance between the centre of the front and rear wheels.

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