Dictionary of Automotive Terms Abbreviations

DICTIONARY OF AUTOMOTIVE TERMS - "Re"

Reach:: The distance from the sealing washer of a spark plug to the end of the thread.

Reactance:: That part of the impedance of an alternating current circuit due to capacitance or inductance or both.

Reaction:: See:
air injection reaction
reinforced reaction injection molding

Reactionary type valve:: A unit which responds to fluid displacement and pressure, or mechanical linkage movement and force, to modulate pressure in a brake cylinder or chamber.

Reaction distance:: The time needed to respond to a situation, translated into the distance required for this, depending on the speed of travel; braking distance plus reaction distance equals the stopping distance.

Reaction injection molding:: (RIM) A processing technique for the production of large foamed automotive components, based on the simultaneous injection of the liquid components and the chemical reaction in the mold. Compare polymerization. In some cases, the components are mixed immediately before being injected into the mold. The term "RIM" is also applied to refer to the plastic material produced by this technique, e.g., "RIM-PUR." Also see reinforced reaction injection molding.

Reaction member:: See stator.

Reaction rate:: See absolute reaction rate

Reactivate:: To restore the tackiness of a completely dried adhesive. Reactivated adhesives are useful in that the adhering surfaces may be coated with adhesive and the surfaces mated again after short term exposure. Reactivated bonds set almost immediately

Reactivation, heat:: To restore the tackiness of the adhesive with heat, and then to bond under pressure

Reactivation, solvent:: To restore the surface tackiness in a dry adhesive film with a suitable solvent

Reactive suspension:: See electronic ride control.

Reactor:: See:
stator
thermal reactor

Reactor one-way clutch:: See stator roller clutch.

Read:: Trucker slang for Hear as in "Can you read me there Baylor."

Reader:: See fault reader.

Read only memory:: (ROM) A non-volatile memory that stores information permanently. Information is placed into the memory at the time of manufacture and cannot be altered after the manufacturing process.

Real-time four-wheel drive:: An automatic four-wheel drive engagement by means of an electro-hydraulic clutch or a viscous coupling incorporated in the drivetrain.

Ream:

To enlarge (e.g., worn valve guides) with a reamer.
To finish a hole accurately with a rotating fluted tool.

Reamer:: A conically or cylindrically shaped tool with longitudinally cut teeth for manual or machine operation, used for precision finishing of bores.
Also See:
terminal reamer
tubing reamer
valve guide reamer

Rear:: The back of a vehicle or component.
Also See:
five-link rear suspension
folding rear seats
four-link rear suspension
heated rear window
independent rear suspension
multi-link independent rear suspension
multi-link rear suspension

Rear apron:: See rear valance.

Rear-axle:: The shaft on which the back wheels revolve.
Also See:
front-axle and rear-axle split
twist-beam rear axle

Rear axle crossmember:: A tubular frame member at the rear of the body shell that incorporates the mounting points for the rear axle, e.g., on the VW Beetle and the Porsche 911.

Rear axle differential:: A differential situated in the final drive of the transmission assembly in a conventional rear-wheel drive vehicle.

Rear axle housing:: The component which connects the drive shaft to the axle shafts.
Also See:
banjo type
split type

Rear axle housing, banjo type:: A rear axle housing from which the differential unit may be removed while the housing remains in place on the vehicle. The housing is solid from side to side.

Rear axle housing, split type:: A rear axle housing made up of several pieces and bolted together. The housing must be split apart to remove the differential.

Rear axle ratio:: The number of times the rear wheels turn compared to a particular transmission speed. The higher the rear axle ratio, the slower the engine can run and still allow the vehicle to achieve a given speed. Also called "Final axle ratio.".

Rear-axle split:: See front-axle and rear-axle split.

Rear bulkhead:: The vertical panel across the width of the car that extends behind the rear seat backrest and separates the interior from the trunk.

Rear bumper skirt:: A rear bumper with integral skirt; a large plastic molding.

Rear cabin pillar:: See C-pillar.

Rear corner panel:: The bottom corner of the rear fenders. For manufacturing reasons, often a separate panel.

Rear corner valance:: The bottom corner of the rear fenders. For manufacturing reasons, often a separate panel.

Rear deck:: The surface of the rear of a sedan which includes the lid of the trunk.

Rear deck panel:: The sheet metal panel extending from the bottom of the rear window to the rear panel and enclosing the cutout for the trunk lid, extending sideways to the top of both rear fenders. In some cases, this panel covers only the area between the bottom of the rear window and the front edge of the trunk lid.

Rear derailleur:: A bicycle component that moves the chain across the rear cogs thus changing the gear ratio and achieving what is referred to as a gear shift.

Rear differential:: A differential situated in the final drive of the transmission assembly in a conventional rear-wheel drive vehicle.

Rear end:: The rear part of the body shell, extending approximately from the rear seat pan to the rear apron of the car, incorporating the trunk floor.

Rear end lift:: The tendency of the back of a speeding vehicle to rise, reducing traction. It can be counteracted by a spoiler.

Rear engine:: An engine located at the rear of a vehicle but outside the wheelbase (i.e., behind the rear wheels). Compare front engine and mid-engine car.

Rear fender:: The body panel which partially encloses a rear wheel.

Rear fog lamp:: A red light with the same intensity as a brake light.

Rear fog light:: A red light with the same intensity as a brake light.

Rear head restraints:: (rhr) head rests located on the back passenger seats.

Rear-hinged door:: A older type of door construction that had the hinges at the rear of the door so that the opening was toward the front (i.e., opposite to modern car doors).

Rear lamp cluster:: A group of lights at the rear corners of a vehicle, commonly comprising: tail lamp, brake lamp, back-up lamp, rear fog lamp, reflector, and signal light.

Rear light surround:: A separate panel spot-welded at the juncture between the trailing edge of the rear fender and the rear valance to provide a mounting base for the rear lights.

Rear license plate lamp:: A white light illuminating the rear license plate.

Rear license plate light:: A white light illuminating the rear license plate.

Rear panel:: A British term for back panel.

Rear quarter panel: Often integral with the rear fender on newer cars, but a separate panel above the rear fender. There may be both an inner and outer panel which makes up the construction.

Rear quarter valance:: See rear corner valance.

Rear seat belt:: An inertia reel belt attached at each end of the rear seats; a passenger riding in the middle of the rear seats must be satisfied with just a lap belt, which many safety experts regard as inadequate. Some manufacturers (notably those from Scandinavia) are tackling the somewhat costly problem and providing secure lap and shoulder belts for all passengers riding in the rear seats.

Rear seats:: See:
folding rear seats
split folding rear seats
split rear seats

Rear sets:: Racing-style footrests mounted toward the rear of the machine to allow the rider to adopt a racing crouch.

Rear shelf:: The interior shelf extending over the trunk at the level of the top of the rear seats.

Rear side window:: One of several types of side body glass: the side window between the B-posts and C-posts of two-door sedans and coupes, the rearmost side window of station wagons between the C-post and D-post, i.e., behind the rear seat backrest, and the third side window found on some four-door sedans behind the rear side doors.

Rear spoiler:: An aerofoil mounted on the rear deck or trunk, typically made of shock-resistant polyurethane with paintable matt black finish. It is effective only at high speeds, but frequently used for the sake of appearance. Most sports cars are equipped with front and rear spoilers (air dams and rear spoilers) to improve the aerodynamic performance by reduced lifting force.

Rear suspension:: The axles, springs, and linkages which control the movement of the rear wheels.
Also See:
five-link rear suspension
four-link rear suspension
independent rear suspension
multi-link independent rear suspension
multi-link rear suspension

Rear tack strip:: A fixed or hinged bar on a convertible top which holds the rear end of the hood against the rear deck.

Rear triangle:: A bicycle frame triangle formed by the chainstays, seatstays, and the seat tube.

Rear valance:: A separate panel set below the rear panel which extends approximately from behind the rear bumper downward to protect the rear end from splashes of mud. In designs with a single-piece rear panel that incorporates the rear valance, the whole area is sometimes referred to as the rear valance or rear panel.

Rearview mirror:: An interior mirror which allows the driver to see behind him.

Rear wash/wipe system:: An electrical system for cleaning the rear window, comprising a water pump, reservoir, and wiper.

Rear-wheel drive:: (RWD) A configuration in which the rear wheels of the vehicle are driven.

Rear-wheel drive transaxle:: A rear-wheel drive construction incorporating a transmission-differential unit placed between the rear wheels of a front-engined car. The engine may be a front engine (as in most cars and all trucks), a mid-engine (as in some sports and racing cars), or a rear engine (as in some city cars, VW Beetle, the Porsche 911 series, and most buses); RWD ensures good acceleration without wheelspin even on cars with powerful engines; on most small cars, RWD has been superseded by front-wheel drive.

Rear wheel skirt:: See fender skirt.

Rear wheel spat:: British term for fender skirt.

Rear window:: The central window at the rear of a vehicle. Although the American term is backlight, most Americans still call it the rear window or back window. Also see heated rear window.

Rear window heater system:: A heating element that removes the fog, mist, or even ice from the inside and outside of the rear window (i.e., backlight).

Rear window heating:: See rear window heater system.

Rear window louvres:: A plastic molding attached to the rear window which deflects sun rays to keep the interior cool; usually hinged to lift up for easy window cleaning.

Rear wiper:: A window wiper that cleans the rear window.

Réaumur scale:: A temperature scale where the freezing point of water at 1 atmosphere is 0° and its boiling point is 80° at the same pressure. Thus 1°C = 0.8°R. The scale was named after the French physicist, René Antoine Ferchault de Réaumur (1683-1757)

Reboard system:: A child restraint system typically installed backwards on the front passenger seat and having the benefit that the child's relatively heavy head is pressed into the back of the child seat instead of being displaced forward in a frontal crash. A system initially available only for babies, but originating from Sweden, they are increasingly offered for children up to six years old; some reboards cannot be used in conjunction with a passenger-side air bag system.

Rebore:: To grind out a worn or damaged cylinder usually .25 mm or (.01") at a time to fit an oversize piston.

Rebound:: The action of a shock absorber to spring back to its fully extended state. The opposite of rebound is jounce.
Also See:
bump and rebound
jounce and rebound

Rebound clip:: A metal clip that holds the leaves of a multi-leaf spring together to keep them from separating sideways.

Rebound damping:: While compression damping controls the movement as the shock compresses as it hits a bump, rebound damping contols the movement as the shock extends back to its relaxed position.

Rebound stroke:: The downstroke of a piston in a damper or shock absorber. Compare compression stroke.

Rebuild:: To disassemble a particular device, clean it thoroughly, replace worn parts, and reassemble it. Also called "overhauling" or "recondition.".

Rebuilt engine:: An engine reassembled using either new parts or reconditioned components.

Recap:

Adding a top strip of synthetic or reclaimed rubber to buffed and roughened surface of a worn tire.
The top strip itself

Also See:
retread

Recharge:: The action of bringing a product back to its full or original level. Recharging a battery brings the voltage back to its recommended level. Recharging the air conditioner means filling the system with refrigerant.

Receiver:

(e.g., of radio remote control system) device that receives incoming electrical or radio signals. The opposite is transmitter.
A steel tubing and channel structure that accepts the ball-mount platform of a removable trailer coupler.

Also See:
air receiver
air tank

Receiver-dehydrator:: Storage tank and filter for liquid refrigerant and containing a drying agent to remove moisture from circulating refrigerant. Also called receiver-drier.

Receiver-drier:

A device on the high side of an air-conditioning system, somewhere between the condenser and the expansion valve, which stores excess refrigerant and removes moisture from the refrigerant; consists of a tank, a filter, a drying agent, a pick-up tube, and, on some units, a sight glass. Also called receiver-dehydrator
A container for storing liquid refrigerant and a desiccant. Used in Chrysler Corporation and some import vehicles Compare accumulator-drier.

Receiver extension:: Used with Receiver Hitch Racks when the rack need to clear obstacles on the back of the vehicle (such as a spare tire rack).

Receiver heating element:: Electrical resistance mounted in or around liquid receiver. It is used to maintain head pressures when ambient temperature is low.

Recess:: See combustion chamber recess.

Recessed spark position:: A position where the spark gap is actually in the shell of the spark plug. It is used for racing and special engines.

Rechargeable battery:: See storage battery.

Reciprocating:: Back and forth motion in a straight line.

Reciprocating action:: A back-and-forth or up-and-down movement such as the action of the pistons.

Reciprocating compressor:

A positive displacement compressor with pistons that move back and forth in cylinders; rarely used for supercharging, more frequently used for air conditioning
Compressor which uses a piston and cylinder mechanism to provide pumping action.

Reciprocating engine:: An engine with a piston that moves to and fro, coming to a standstill at each reversal.

Reciprocating pump:: See piston charging pump.

Reciprocating single piston pump:: A pump having a single reciprocating (moving up and down or back and forth) piston.

Reciprocation:: A back-and-forth or up-and-down movement such as the action of the pistons.

Recirculating ball:: See recirculating-ball-and-nut steering.

Recirculating ball and nut steering:: See recirculating-ball-and-nut steering.

Recirculating-ball-and-n ut steering:: A very popular type of steering gear. It uses a series of ball bearings that feed through and around and back through the grooves in the worm gear and nut on the steering shaft. The turning forces are transmitted through these ball bearing to a sector gear on the pitman-arm shaft. When the steering wheel is turned, the worm gear on the end of the steering shaft rotates and the movement of the recirculating balls causes the ball nut to move up and down along the worm. Movement of the ball nut is carried by teeth to the sector gear which in turn moves with the ball nut to rotate the pitman-arm shaft and activate the steering linkage. The balls recirculate from one end of the ball nut to the other through a pair of ball return guides. This system is also called ball-and-nut steering or worm-and-recirculating-ball steering.

Recirculating ball gearbox:: A special version of the worm-and-nut steering in which ball bearings circulate between the nut and worm to reduce friction. Turning the steering wheel rotates the worm gear, which causes the ball nut rack to move up or down. Teeth on the outer edge of the ball nut rack mesh with the sector gear so that as the rack moves, it swivels the sector gear and Pitman arm. The ball bearings in the grooves reduce friction.

Recirculating ball steering:: A special version of the worm-and-nut steering in which ball bearings circulate between the nut and worm to reduce friction. Turning the steering wheel rotates the worm gear, which causes the ball nut rack to move up or down. Teeth on the outer edge of the ball nut rack mesh with the sector gear so that as the rack moves, it swivels the sector gear and Pitman arm. The ball bearings in the grooves reduce friction.

Recirculating ball worm and nut:: See recirculating-ball-and-nut steering.

Recirculation:: See:
exhaust-gas recirculation
fuel vapor recirculation system

Recirculation system:: See fuel vapor recirculation system.

Reclaimed rubber:: Reprocessed rubber (tires, inner tubes, rubber novelties), either synthetic or natural, used as an adhesive base. Because of characteristic advantages of low cost, good physical properties, wide tack range, tolerance of surface preparation, and high wet strength, these are the most widely used of the rubber based adhesives

Recognition:: See voice recognition.

Recon:: A colloquial term for reconditioned engine.

Reconditioned engine:: A worn engine that has been given a new lease of life by reboring the cylinders, regrinding the crankshaft journals and generally replacing any worn or damaged parts.

Recorder:: See:
crash recorder
trip recorder

Recording ammeter:: Electrical instrument which uses a pen to record amount of current flow on a moving paper chart.

Recording thermometer:: Temperature measuring instrument' which has a pen marking a moving chart.

Recovery:: See:
breakdown recovery
vapor recovery

Recovery/recycling equipment:: Equipment that must now be used when servicing air conditioner systems. This equipment captures refrigerant removed from an air conditioning system and stores or recycles it.

Recovery system:: See:
coolant recovery system
vapor Recovery System

Recreational vehicle:

(RV)

Any vehicle (motorized or trailered) in which temporary camping is done. They are divided into seven categories:
.
A British term for any vehicle used for pleasure rather than business or transport (e.g., dune buggy, quad) (i.e., an ATV).

Rectangular headlight:: A modern shape of headlight as opposed to the traditional circular headlight.

Rectangular-section ring:: A compression ring with a rectangular cross-section.

Rectification:: The process of changing AC to DC.

Rectifier:: A device used to change AC ( alternating current) into DC (direct current). Some small motorcycles use a single diode for this purpose (half-wave rectifiers), the overwhelming majority use four diodes connected in a bridge which yields full-wave rectification.
Also See:
diode
full-wave rectifier
half-wave rectifier

Rectifier diode:: A semiconductor diode in an alternator that converts alternating current to direct current.

Rectifier, electric:: Electrical device for converting ac to dc.

Rectifier pack:: A diode heat sink with diodes in an alternator.

Recumbent:: A bicycle in which the rider sits low between the two wheels. The seat is "L-shaped." The rider's back is against the upright portion of the seat. His feet are almost straight forward. The pedals are just behind the front wheel. The handlebar is located below the rider.

Recuperative coil:: Secondary coil in glycol water forced-air furnace which extracts latent heat from combustion gases.

Recycling:: Passing of flue gases from combustion in a furnace to a secondary heat exchanger to remove latent heat.
Also See:
charge-air recycling
vapor recycling

Recycling car:: A car built with recycled materials and designed so as to facilitate recycling.

Red flag:: A solid red flag is used to stop the race immediately. Generally races are stopped for bad accidents or weather. Occasionally, a multiple car pileup will halt a race. Wreckers and fire marshals clear the track of cars, debris and fluids. Alternatively, rain makes the surface of the race track dangerous. Once NASCAR officials authorize the race to start again, a green flag resumes the race.

Red lead:: (pronounced "LED") A poisonous, bright-red powder, soluble in excess glacial acetic acid and dilute hydrochloric acid; used for corrosion protection.

Red line:

Top recommended engine rpm. If a tachometer is used, it will have a mark (red line) indicating maximum rpm. Some tachometers mark the red line with a colored sector. Others have two lines: the lower one marking the maximum allowable sustained engine rpm, the higher line indicating the absolute maximum rpm.
(RL) Tires with a red concentric line which were marketed in the late '60s and early '70s.

Reduced shank:: A shank whose diameter approximately equals the effective pitch diameter.

Reducer:: The solvent that is used to thin enamel.
Also See:
thinner
general purpose lacquer thinner

Reducer valve:: See vacuum reducer valve.

Reducing adapter:: An adapter whose male end for the socket is smaller than the female end for the drive handle. Opposite to increasing adapter.

Reducing agent:: A material which adds electrons to an element or compound in chemical reactions, i.e., which increases the positiveness of its valence.

Reducing catalyst:: A catalyst such as rhodium which converts nitrogen oxides into harmless nitrogen and oxygen in a reducing catalytic converter. Compare oxidizing catalyst.

Reducing flame:: An oxygen-fuel gas flame with a slight excess of fuel gas.

Reducing furnace:: A section in continuous galvanizing lines in which the oxygen content of steel surfaces is reduced at 900-980°C by means of hydrogen.

Reduction:: A chemical reaction in which an element gains electrons, i.e., has an increase in positive valence. Compare oxidation.
Also See:
cap cost reduction
capitalized cost reduction
double reduction gearing
noise reduction

Reduction effort:: See supplier cost reduction effort.

Reduction gearbox:: A gearbox located at the wheels, which reduces the drive speed and may also increase ground clearance; often found on 4WD off-road vehicles.

Reduction gearing:: See double reduction gearing.

Reduction of area:: Difference in cross sectional area of a specimen after fracture, as compared to original cross sectional area.

Reed:: A part of a reed valve made of flexible steel, or of glass fiber reinforced resin, attached to the valve case and normally closed. The reeds are designed to open readily under pressure from the incoming mixture, but will close rapidly once the pressure inside the crankcase reaches that of the surrounding atmosphere; in this way, the maximum amount of mixture is admitted and any back-leakage is prevented.

Reed stop:: A component of a reed valve used to limit upward travel of the reed.

Reed valve:

A one-way valve used in a two-cycle engine. It is made of a flat strip of metal that lies on the floor of the crankcase over a hole connected to the carburetor. As the piston moves up, the vacuum developed in the crankcase lifts the reed valve off the hole. The vacuum causes the fuel-air mixture to flow from the carburetor into the crankcase. Then, as the piston starts to move down, pressure increases in the crankcase pushing the reed valve down, closing the hole and sealing the crankcase.
Wafer-thin metal plate located in the valve plate of an automotive compressor which act as suction and discharge valves. The suction valve is located on the underside of the valve plate; the discharge valve is situated on the top.

Reed valve induction timing:: Using a reed valve located in the intake system to control induction timing.

Reefer:

A refrigeration unit which is mounted on a large truck to cool the contents in the trailer.
A refrigerated trailer with insulated walls and a self-powered refrigeration unit. Most commonly used for transporting food.
A ship designed for carrying goods requiring refrigeration.

Reefer container:: An insulated container fitted with a refrigeration unit for carrying cargo requiring temperature control.

Reel:: A revolving, often cylindrical device for winding up or letting out cord, wire, or strap.
Also See:
inertia reel seat belt
inertia reel
locking reel

Reel seat belt:: See inertia reel seat belt.

Reface:: A general term for reconditioning of the interface between valves and their seats in the cylinder head; depending on valve seat condition, refacing may involve lapping, grinding, or cutting.

Reference ignition pattern:: An oscilloscope pattern of an intact ignition system for comparison purposes.

Reference input:: In a closed-loop control, the reference input is fed to a controller that changes a controlled variable in a controlled system to achieve a certain output condition or actual value.

Reference mark sensor:: A magnetic pick-up attached to the flywheel for sensing the crankshaft position and transferring the signal to the electronic control unit, which calculates the ignition point; the reference mark sensor scans a pin or a hole in the flywheel and produces one output signal per crankshaft revolution.

Reference pressure:: The fuel bowl is vented to the outside air to maintain a constant (atmospheric) pressure on the fuel, thus maintaining a constant fuel level as a point of reference for the other system in the carburetor.

Reference signal:: A signal sent to the ECU, generally by the vehicle's fastest-moving wheel, which the ECU uses for comparison with the signals from decelerating wheels

Reference temperature:: The temperature at which measuring tools and pieces being worked on must have the specified measurements; the reference temperature 20°C applies to all statements of technical measurements unless the contrary is expressly stated.

Reference voltage:: A voltage provided by a voltage regulator to operate potentiometers and other sensors at a constant level.

Refinishing:: See paint refinishing.

Refinishing paint:: A paint sold specifically for resprays; many paint formulas used in the factory are not suited for respray equipment, so special paints for the repair trade are required.

Refinish system:: The complete product lines and product support offered by many paint manufacturers for respray operations in body shops; these include all materials from primers and thinners to the topcoat plus additional respray products; all products are matched for optimum results.

Refit:: Closure of a plant for the purpose of plant conversion or retooling.

Reflectance:: The ratio of reflected luminous flux to that reflected from an ideal, perfectly reflecting surface when similarly illuminated.

Reflection:: See abnormal reflection

Reflector:

A part of a headlight which receives light from the bulb and reflects it back through the lens.
A part of a rear lamp cluster which reflects the light from headlights behind.

Also See:
parabolic reflector
triangular safety reflector

Reformulated gasoline:: (RFG) Fuel with less volatility and reduced levels of toxic hydrocarbons.

Reformulated gasolines:

(RFG)

Fuels with less volatility and reduced levels of toxic hydrocarbons.
Gasoline blended with pollution reducing additives

Refrigerant:: The liquid used in refrigeration systems to remove heat from the evaporator coils and carry it to the condenser. It absorbs and gives up heat as it changes from a liquid to a gas to a liquid. Freon-12 was a common automotive refrigerant, but it has been replaced by C134A.

Refrigerant-12:: The name applied to refrigerant generally used in automotive air conditioning systems and refrigerators. Also called freon-12.

Refrigerant charge:: Quantity of refrigerant in a system.

Refrigerant control:

Device which meters flow of refrigerant between two areas of a refrigerating system. It also maintains pressure difference between high-pressure and low-pressure side of the mechanical refrigerating system while unit is running.
Device used to regulate flow of liquid refrigerant into evaporator. Can be a capillary tube, expansion valves, or high-side and low-side float valves.

Refrigerant cylinder:: Cylinder in which refrigerant is stored and dispensed. Color code painted on cylinder indicates kind of refrigerant.

Refrigerant dye:: Coloring agent that can be added to refrigerant to help locate leaks in a system.

Refrigerated truck:: Commercial vehicle equipped to maintain below-ambient temperatures,

Refrigeration cycle:: The complete circulation of refrigerant through an air conditioning system as it changes temperature and pressure, i.e., changes its state from vapor to liquid, then back to vapor. Air-conditioning refrigerant in vapor form is pressurized in the compressor, air-cooled in the condenser, and becomes a liquid which passes through the receiver-drier into the expansion valve where it expands into low-pressure liquid. It then flows through the evaporator where it expands again and starts to boil, absorbing heat from the core and cooling the air going into the passenger compartment. The compressor draws off the low-pressure vaporized refrigerant and recycles it.

Refrigeration oil:: A highly refined lubricating oil which is free of contaminants such as sulphur, moisture, and tar.

Refrigerator:: See absorption refrigerator

Refundable deposit:: This is a refundable deposit required at lease inception. In some cases it may be used to satisfy the final monthly payment. It is sometime called a security deposit.

Regal:: A model of automobile manufactured by Buick
Click image for books on Buick Regal

Regenerative braking:: A system in which an electric motor can be switched to a generator mode when braking, so that the kinetic energy involved may be stored in the battery.

Register:

To align with. The two-stroke piston is provided with cut-outs that line up with the intake ports as the piston moves up and down in the bore, i.e., they register with the ports. The fresh charge can thus enter the crankcase.
Combination grille and damper assembly covering an air opening or the end of an air duct.

Registered keeper:: A British term for a person who keeps the car, i.e., who is registered and pays tax and insurance for the car, but is not necessarily the owner or the driver.

Registered owner:: The person who owns the car, i.e., the car is registered in his name and he pays the licence, tax, and insurance for the car.

Registered tons:: See gross registered tons.

Registration:

Motor vehicle ownership that is filed with the province/state.
The act of entering the details of a new vehicle in a supervised record.

Registration document:: Papers giving details of a vehicle, including its manufacturer, date of registration, engine and chassis numbers, and owner's name. Also see vehicle registration document.

Registration number:: A unique sequence of letters and numbers assigned to a vehicle when it is registered, usually indicating the year and place of registration, displayed on the vehicle license plate.

Registration plate:: See license plate.

Registry:: See:
certificate of registry
open registry

Regrind:

To smooth and polish again (e.g., valve seats).
A resin batch material produced by regrinding thermoplastic scrap and waste; such recycled material can be used to produce plastic parts which are not critical in terms of engineering properties or color, such as wheel arch liners or battery cases. The opposite is virgin resin.

Regrooveable tire:: See special mileage tire.

Regrooving:: The act of cutting new tread grooves into the crown of the tire after the original tread is worn down. A practice which is legally forbidden in many places.

Regular Cab:: A pickup with two doors (one on each side of the vehicle) and a bed at the back.

Regular gasoline:: Gasoline which has the normal amount of octane and is less than premium or high-test gasoline.

Regular threading:: A common name for right-hand thread

Regulated proportioning valve:: See load-sensitive proportioning valve.

Regulating:: See:
main regulating system
pressure regulating valve

Regulating system:: See main regulating system.

Regulating valve:: See pressure regulating valve.

Regulation traction control system:: See anti-spin regulation traction control system.

Regulator:

The device found in the panel of a vehicle door which lifts and lowers the window. It may be operated manually or electrically.
Any device which controls fluid (gas or liquid) flow, pressure, temperature, voltage, etc.
Also See:
acetylene regulator
current regulator
height regulator
oxygen regulator
pressure regulator valve
pressure regulator
system pressure regulator voltage regulator

Regulator valve:: See pressure regulator valve.

Regulator, voltage:: See voltage regulator.

Reinforce:: To increase the strength of plastics by filling them with whiskers of glass, metal, fibres, etc.
Also See:
glass reinforced filler paste
glass reinforced plastic
hinge pillar reinforcement

Reinforced filler paste:: See glass reinforced filler paste.

Reinforced plastic:: See glass reinforced plastic.

Reinforced reaction injection molding:

(RRIM)

A reaction injection molding of reinforced plastics.
The term also refers to the material produced by this technique. Compare reaction injection molding.

Reinforcement:: Any material, usually rubber and fabric, vulcanized to the tire to return strength to the cord body upon an injury. Also see hinge pillar reinforcement.

Reinforcement of weld:: Excess metal on the face of a weld.

Relative atomic mass:: (ram) Mass of atoms of an element formerly in atomic weight units but now more correctly given on the unified scale where 1 u is 1.660 x 10^-27kg, where u is the atomic mass unit. For natural elements with more than one isotope, it is the average for the mixture of isotopes.

Relative density:: The ratio of the mass of a given volume of a substance to the mass of an equal volume of water at a temperature of 4°C. The older term was specific gravity

Relative humidity: (RH)

A dimensionless ratio of the actual vapor pressure of the air to the saturation vapor pressure
Ratio of (difference between) amount of water vapor present in air to greatest amount possible at same temperature.

Relay:

An electro-magnetically operated switch used to make and break the flow of current in a circuit. As low amperage current is passed through one circuit of the relay, it switches and permits a greater current through another line. For example, when installing auxiliary lights with a heavy draw, the stock light switch may not be able to take the current. Thus a relay is installed so that when the light switch is turned on, low current is sent to the relay. The relay closes the circuit of heavy wiring directly from the battery to the lights. Also called "cutout" and "circuit breaker."
An automatic device which controls the setting of a valve, switch, etc. by means of an electric motor, solenoid, or pneumatic mechanism.
An electromagnetic switch using a small amount of current in one circuit to control a second circuit using a greater current flow.
A common practice in the less-than-truckload industry, in which one driver takes a truck for 8 to 10 hours, then turns the truck over to another driver, pony express style. Also called "relay driving"

Also See:
cutout relay
hot-start pulse relay
time delay relay

Relay driving: A common practice in the less-than-truckload industry, in which one driver takes a truck for 8 to 10 hours, then turns the truck over to another driver, pony express style.

Relay emergency valve:: A relay valve which also provides for automatic application of the trailer brakes in case of a breakaway or loss of pressure in the trailer supply (emergency) line.

Relay lever:: See idler arm.

Relay rod:: An intermediate rod between the pitman arm and idler arm.

Relay valve:: See ABS Relay Valve.

Release:: See:
bonnet release
hood release
quick-release
quick release skewer

Release agent:: A substance to prevent a molding, i.e., a GRP part, from sticking to the mold and to facilitate its removal from the mold; as opposed to release wax, this is marketed only in liquid form.

Release bearing:: See clutch release bearing.

Release button:: A button at the end of the park brake lever which, when depressed, allows the pawl to be released from the ratchet.

Release finger:: See:
clutch release finger
clutch semi-centrifugal release finger
semi-centrifugal release finger

Release fingers:: See clutch semi-centrifugal release fingers.

Release fork:: See clutch release fork.

Release lever:: See clutch release lever.

Release skewer:: See quick release skewer.

Release tool:: See trim panel release tool.

Release wax:: See release agent.

Releasing fluid:: Penetrating oil for loosening seized parts.

Relief:: Amount one surface is set below or above another surface.
Also See:
high pressure relief valve
pressure relief valve

Relief passage:: See bypass.

Relief valve:

A valve in the air pump of an air injection system which dumps part of the air at high pump speeds to prevent pump damage. It may be combined with the air gulp valve.
Safety device on a sealed system. It opens to release fluids before dangerous pressure is reached.

Also See:
high pressure relief valve
pressure relief valve

Relieve:: To remove, by grinding, the small lip of metal between the valve seat area and the cylinder and removing any other metal deemed necessary to improve the flow of fuel mixture into the cylinders. Porting is generally done at the same time.

Relieved shank:: See reduced shank.

Relieving:

Removal of some metal from around racing engine valves and between cylinder and valves to facilitate flow of gases.
See stress relieving.

Reline:: To replace the brake shoes in drum brakes.

Reluctance:

A force working against the passage of magnetic lines of force (flux) through a magnetic substance.
The characteristic of a magnetic material which resists the flow of magnetic lines of force through it

Reluctor:: See trigger wheel.

Remains:: See sheet metal remains.

Remanufacturing:: The process of taking a used part and returning it to original equipment (OE) specifications through disassembly and cleaning of the core, testing, and remachining or replacement of worn components.

Re-metalling the bearings:: A bearing repair method used on pre-war engines with poured bearings instead of Babbitt metal inserts. The Babbitt metal is poured into the bearing surfaces and is then scraped until a correct bearing surface is established.

Reminder:: See lights-on reminder.

Remold:: See retread.

Remote:: See:
infrared remote control
ir remote control

Remote bulb:: A sensing device connected to the expansion valve by a capillary tube. The bulb senses the temperature of the evaporator outlet pipe and controls the expansion valve accordingly.

Remote choke:: Vacuum diaphragm is mounted on the carburetor, but the bimetal spring is mounted either on a pad on the intake manifold or in a heat well in the exhaust man. Choke lever is operated by a mechanical linkage rod from the bimetal spring. Also called divorced choke.

Remote control:

The control of something from a distance.
The device used for this.

Also See:
infrared remote control
ir remote control

Remote controller:: Energy control device capable of controlling multiple devices. It can be located away from the devices it is controlling.

Remote-control locking:: A central locking device operated by a remote control from outside the car.

Remote keyless entry:: A system where the door locks can be opened or locked by a small hand-held switching device located several meters/feet away. Some also contain a panic button that causes the lights to flash and the horn to honk if an intruder is seen near the vehicle. Most remote keyless entry devices turn on the vehicle's interior lights while unlocking the driver's door.

Remote mirror:: An outside mirror that is adjusted by a toggle device inside the passenger compartment. Older styles relied on a cable that transferred physical movement from the toggle to the mirror. On newer vehicles, the mirror is controlled by electrical controls.

Remote power element control:: Device with sensing element located apart from operating mechanism it controls.

Remote starter switch:: A special automotive tool that allows the ignition switch to be bypassed for cranking the engine.

Remote system:: Refrigerating system in which condensing unit is away from space to be cooled.

Removable rim:: See detachable rim.

Remover:: A chemical or compound used to clear away unwanted material.
Also See:
bug and tar remover
rust remover
spot-weld remover
stud remover
tar remover
valve guide remover

Renault:: A vehicle brand of which the 45 HP models of 1925-1948 with required application are classic cars.
Click image for books on Renault

Reo:: A vehicle brand of which the 1931-33 Royale 8-31, Royale 8-35, Royale 8-52, and Royale Custom 8 and 1934 N1, N2, and 8-52 are classic cars.

Repair:: To restore something to working condition, e.g., by reconditioning, rebuilding, or replacing.
Also See:
body repair
independent repair shop
plug repair
section repair

Repair and Service Council:: See Canadi an Automotive Repair and Service Council.

Repair gum:: See cushion gum.

Repair kit:: A package of the parts needed to repair a particular component (e.g., carburetor, generator, pump, universal joint, etc.).

Repair link:: A link in some motorcycle chains that can be disassembled for chain repair

Repair manual:: A book which details the procedure for repairing one or more components of a vehicle. Compare service manual.

Repair section:: A special panel supplied for body repairs that does not include the full panel used for assembling the car but only the most vulnerable areas; i.e., for fenders, separate repair sections are supplied for the headlight area and the bottom fender edges, where damage usually occurs. Compare replacement panel.

Repair shop:: See:
independent repair shop
specialty repair shop

Repeater lamp:: A British term for a signal light on the side of a vehicle.

Replaceable derailleur hanger:: A type of derailleur hanger that can be easily replaced using hand tools if it gets damaged

Replacement market:: All products and services used in the repair and maintenance of vehicles.

Replacement panel:: A body panel supplied for repair purposes; sometimes also used to denote a repair section.

Replacement vehicle:: A car loaned by a dealer to a customer while the customer's car is under repair.

Replenishing port:

An opening in the master cylinder body which connects the fluid reservoir to the annulus of the primary piston. Compare compensating port. In a tandem master cylinder, there is one replenishing port for each piston. It is the first port as seen from the pushrod end of the master cylinder and it is always open. Also called a breather port
Breather port
The opening between the fluid reservoir and the low-pressure chamber that keeps the chamber filled with fluid.

Replica panel:: See pattern panel.

Repli-racers:: Hard-edged sportbikes. These motorcycle are characterized by riding positions that tuck the rider into an extreme crouch, forcing him to practically lay down on the fuel tank

Repmobile:: A colloquial term for a car used by a sales representative.

Repro:: Abbreviation for " reproduction.".

Reproduction:: Parts or complete vehicles that have been manufactured to closely follow or exceed original specifications, materials, and performance. Also called "repro" or "repros." These parts often are so perfect that not even a concours judge can tell that they are not NOS or OEM.

Reproduction panel:: See pattern panel.

Repulsion-start induction motor:: An electric motor type which has an electrical winding on the rotor for starting purposes.

Required ignition voltage:: The maximum high voltage required to produce a spark under particular conditions.

RES:

An abbreviation for "resume" on a cruise control switch which sets the cruise speed back to what it was after being shut off.
A ballast resistor.

Research & development:: R&D expenditures (product and process development)

Research and Experimental Development Program:: See scientific Research and Experimental Development Program.

Research octane number:: (RON) A fuel octane rating determined by the research octane test, one of many test procedures. Compare octane number.

Reseat:: To recut a valve seat after repeated grinding-in has worn it out of shape.

Reservation:: See:
central reservation
central reserve

Reserve:: The amount left in the fuel tank. On many motorcycles there is no gas gauge. Instead, the fuel tap has two settings. The regular setting allows most of the fuel to be used. When this amount is finished, the fuel tap can be adjusted so that the remaining portion can be used. During this time, it is wise to fill up the tank.
Also See:
central reserve
heat range reserve
high-voltage reserve
voltage reserve

Reserve capacity:: The time, in minutes, that a battery can maintain a discharge rate of 25 amps.

Reservoir:

Any container filled with fluid.
The space between the outer and inner tubes of a double-tube shock absorber which takes up the oil squeezed out of the working chamber corresponding to the volume of the piston rod immersed in the working chamber.
A container attached to the master cylinder, either directly or by hoses, that stores extra brake fluid for the hydraulic system

Also See:
brake fluid reservoir

Reservoir diaphragm gasket:: The gasket under the master cylinder reservoir cap separating the fluid from the atmosphere. Moves with fluid to allow venting above the fluid.

Reset button:: A switch which puts the configuration of a component back to its standard setting.

Reshaping:

A panel beating process for removing dents: the panel is brought roughly into its original shape before detailed work is performed in the finishing stage.
The process of forming a panel from sheet steel.

Residual:: See expected residual value.

Residual brake pressure type check valve:: A two-function unit in which one function either restricts fluid from the brake wheel cylinder(s) or retains a pressure in the brake wheel cylinder(s) at the time of brake release, and in which the other function permits fluid compensation for fluid volume changes.
Also See:
check valve
closed type check valve
open type check valve
residual pressure valve
two-way type check valve

Residual check valve:: See check valve closed type check valve open type check valve residual pressure valve residual brake pressure type check valve two-way type check valve

Residual discount:: If the end-of-lease purchase price (stated residual value) is greater than the expected end-of-lease value (expected residual value), the dollar difference represents the value of the vehicle that you will not pay for during the lease.

Residual exhaust gases:: The exhaust gas remaining in the cylinder of a two-stroke engine after the exhaust ports have been closed, i.e., these gases have not been scavenged.

Residual penalty:: If the end-of-lease purchase price (stated residual value) is less than the expected end-of-lease value (expected residual value), the dollar difference represents the additional value of the vehicle you'll pay for during the lease.

Residual pressure:

Fuel pressure maintained within the system after engine shutdown.
Pressure remaining in a hydraulic circuit after the brakes have been released

Residual pressure check valve:: A small valve, usually located in the outlet port(s) of the master cylinder, which maintains a certain amount of positive pressure in the hydraulic circuit(s) when the brakes are released.

Residual pressure valve:: A valve mounted in the cylinder outlet between piston and brake lines of drum brake circuits. It maintains a certain minimum pressure in the system. Disc brakes do not require a residual pressure valve.

Residual value:: See:
stated residual value
expected residual value

Residue:: See combustion residue.

Resilience:: Capability of a sealer or coating to return to is original size and shape after deformation

Resilient mounting:: A suspension system or cushioned mounting designed to reduce the transmission of normal electric motor noise and vibration to the mounting surface

Resin:

A secretion from trees used in varnishes, printing ink, and plastic as a binder.
A synthetic product with some of the same physical properties as the plant secretion.
A liquid plastic used in body work.
Synthetic plastic adhesive.

Also See:
acrylic resin
epoxy resin
gel-coat resin
lay-up resin
virgin resin

Resist:: A substance applied onto aluminum pieces before etching; no surface particles are removed where the surface is covered with the protective coating.

Resistance:

An opposing force.
A measure of a conductor's ability to retard the flow of electricity.
An opposition to flow or movement; a coefficient of friction.
(R) The degree of obstacle presented by a material to the flow of electrical current. Resistance is measured in ohms. R is the symbol

Also See:
air resistance
corrosion resistance
fatigue resistance
impact resistance test
internal resistance
knock resistance
polarization resistance
rolling resistance
roll resistance
surface resistance
wear resistance

Resistance, electrical:: The difficulty electrons have moving through a conductor or substance.

Resistance shrinking:: Ripples in the bodywork are removed by shrinking the panel with the aid of heat from an electric current provided by the electrode of a special tool which is brought into contact with the rippled area.

Resistance test:: See impact resistance test.

Resistance thermometer:: An electrical temperature sensor which, in contrast to a thermocouple, needs an external voltage supply; the actual sensing element is a resistor whose resistance is an accurate indication of the temperature.

Resistance welding:: Fusing metals using the resistance of the metals to the flow of electricity, as the source of heat.

Resistant:: See:
impact-resistant
weather resistant

Resistivity:: The ability of a material not to conduct electricity. The opposite is conductivity.

Resistor:

A device placed in a circuit to lower the voltage. It will also decrease the flow of current.
Electrical device that is a poor conductor of electricity and produces a given amount of resistance to current flow.

Also See:
ballast resistor
coil resistor
ignition coil resistor
load resistor

Resistor spark plug:: A spark plug containing a resistor designed to shorten both the capacitive and inductive phases of the spark. This will suppress radio interference and lengthen electrode life. Using a non-resistor spark plug may also damage a CDI box.

Resleeve:: See re-sleeve.

Re-sleeve:: This is a term used of the piston cylinders. The old cylinder inserts are completely removed and new inserts or sleeves are pressed in. This action is done when the cylinder cannot be rebored. Also see cylinder sleeve.

Resonator:

A small muffler-like device that is placed into the exhaust system near the end of the tail pipe. It is used to provide additional silencing of the exhaust.
Any device that attenuates pressure spikes.

Resource Conservation and Recovery Act:: Federal act that covers businesses that generate, transport, or manage hazardous wastes.

Response:: See steering response.

Respray:: To add one or more coats of paint to the existing finish. Also see partial respray.

Rest:: See:
armrest
backrest
start from rest

Restoration:: The act of working on a vehicle with such care as to bring it back to its original condition (including original parts, paint, chroming processes, etc.) rather than merely rebuilding or repairing one.

Restorationitis:: A term coined by Mark A. Rock of Columbia Station, OH. A quasi-disease which affects a person with a restorable vehicle so that he feels compelled to work on his vehicle rather than eat, sleep, or anything else. While working on his vehicle to repair or replace a particular part, the "disease" compels him to disassemble, clean, polish, repair, etc. everything associated with the initial part and he justifies his actions by saying, "While I am at it, I might as well do it right." Also see detailitis.

Restorer:: See finish restorer.

Restraint:: A device used to halt the movement of something.
Also See:
head restraint
child restraint system
passive restraint system
rear head restraints
supplementary inflatable restraint
voluntary Export Restraint

Restraint Agreement:: See Voluntary Restraint Agreement.

Restraint inflatable air-bag system:: See supple mental restraint inflatable air-bag system.

Restraint system:: A general term for occupant safety systems such as seat belts, belt tensioners, air bags, child seats, etc.
Also See:
airbag restraint system
child restraint system
passive restraint system
supplemental restraint system

Restrictor:

A porous device located in vacuum lines to delay vacuum applied to diaphragms.
A device for producing a deliberate pressure drop or resistance in a line by reducing the cross-sectional flow area.
See nozzle restrictor.

Restrictor plate:: A plate attached to the carburetor that limits the amount of airflow entering the combustion chamber. It decreases horsepower.

Rest stop:: A place at the side of a road where drivers can stop (to rest). The British term is "lay-by".

Rest-um-up:: Trucker slang for Roadside rest area as in "Can anyone tell me where the next eastbound rest-em-up is?"

Resume:: A switch on the cruise control system. If you are driving on cruise control, for example at 100 kph, and approach some slow traffic, you would normally apply the brakes. This action will disengage the cruise control and allow you to slow down. Once you are past the slow traffic, you can go back to the speed you had previously set by simply hitting the "resume" button. The vehicle will accelerate to that speed.

Resurfacing:

If the cylinder head is warped due to thermal differences, its mating surface will have to be machined to ensure first that a level surface is created and second that the engine's compression ratio is not increased above a tolerable value.
The process of machining a brake drum or disc on a brake lathe to remove surface imperfections from the friction surface. Resurfacing is also done after a rotor is turned to give the friction surfaces a non-directional finish.

Retail:: The price of something that the customer pays (in contrast with wholesale). See manufacturer's suggested retail price.

Retail price:: See manufacturer's suggested retail price.

Retainer:: A device which holds something in place.
Also See:
pad retainer pin
pad retainer
valve keeper
valve retainer
valve spring retainer

Retainer pin:: See pad retainer pin.

Retainer plate:: A plate which prevents a valve from sliding out of its bore.

Retainer spring tool:: A special automotive tool used on drum brakes for restraining the shoe retaining springs for removal and installation. It comes in a variety of shapes, e.g., as a screwdriver-type tool with a special socket end to grip retaining washers.

Retaining key:: A metal plate used to secure some sliding calipers in their anchor plates.

Retaining ring:: See truarc retaining ring.

Retaining spring:: A spring used to connect the lower ends of a pair of brake shoes and to hold them in contact with the star wheel adjuster.

Retard:

To set the ignition timing so that a spark occurs later or less degrees before TDC. It involves adjusting the camshaft, distributor spark, or valve operation. In this way, the spark plugs fire or the valves open later in the cycle.
The device for doing this action.
The opposite of advance.

Also See:
ignition retard
spark retard
vacuum retard

Retarded:: Occurring late.

Retarder:

An additive to decrease the evaporation rate of a thinner or reducer in paint; used to improve viscosity in hot weather.
An auxiliary brake used on commercial vehicles and coaches (it is a requirement in some European countries). The most common type is called a "Jake Brake""Jake Brake" because the predominant manufacturer is Jacobs Vehicle Equipment Co. Other types of retarders include exhaust retarders, transmission-mounted hydraulic retarders and axle-mounted electromagnetic retarders. Also called energy retarder, or engine brake.

Also See:
energy retarder

Retard unit:: See vacuum retard unit.

Retract:: To draw back, pull back, or rewind.

Retractable aerial:: A telescopic aerial or power antenna.

Retractable antenna:: See power antenna.

Retractable headlights:: See concealed headlights or hideaway headlights.

Retracting spring:: Used to pull the brake shoes away from the drum when the brake pedal is released. Also pushes the wheel cylinder piston back into its bore, returning the brake fluid to the master cylinder.

Retractor:: A seat belt device which locks the reel of a seat belt when the forward acceleration of the occupants exceeds a certain value.
Also See:
belt retractor
headlight retractor indicator lamp

Retractor indicator lamp:: See headlight retractor indicator lamp.

Retread:

A means of extending the life of a tire that has worn its original tread, yet still has a sound carcass. The casing is prepared by buffing off tread rubber and vulcanizing new tread rubber stock in its place.
A casing to which tread rubber has been affixed to extend the useable life of the tire after the original tread has been worn out.
The term in some parts of the USA and Australia is "recap." Also see production retread shop.

Retreading:: See retread.

Retread shop:: See production retread shop.

Retrofit:: To equip a vehicle with new parts after it has been manufactured.; Term used in describing reworking an older installation to bring it up to date with modern equipment or to meet new code requirements.

Return:: See:
earth return
fuel return line
ground return

Return line:: See fuel return line.

Return spring:

A spring which is attached to a lever so that when the lever is moved in one direction, the spring forces it back.
Springs used on drum brakes to pull the brake shoes away from the drums when the brakes are released

Also See:
brake shoe return spring
throttle return spring

Return sweep:: A body panel section presenting a concave appearance; its most common function is to strengthen loose panel areas such as the finish along the wheel aperture of the fender.

Rev:: Abbreviation for revolution.

Rev counter:: A colloquial term for tachometer.

ReVere:: A vehicle brand of which the 1925-1948 models are classic cars.

Reverse:

To drive backward or to back up.
Reverse gear (R). Also see auto reverse.

Reverse bias:: Nonconductive condition that exists when current flow is blocked by a diode.

Reverse bleeding:: A method of purging air from a hydraulic system by forcing fluid into the system at a bleeder valve and allowing the air to escape at the master cylinder.

Reverse brake shoe:: See trailing brake shoe.

Reverse clutch:: A clutch which couples the components of planetary gear sets or trains in such a way that the vehicle can be driven backwards.

Reverse cycle defrost:: Method of heating evaporator for defrosting. Valves move hot gas from compressor into evaporator.

Reversed Elliot axle:: An axle design in which the axle beam terminates in an eye, the steering knuckle axis dividing as a yoke or fork-shaped end which straddles the axle beam end.

Reversed polarity:: (Electrode positive-anode) referring to DC and causing electrons to flow from the base metal to the electrode.

Reverse Elliot steering knuckle:: Type of axle construction in which steering spindle straddles ends of axle beam.

Reverse-Elliot type axle:: A solid bar front axle on which the steering knuckles span or straddle the axle ends.

Reverse-flow scavenging:: A scavenging system for two-stroke engines in which a cylinder has two pairs of transfer ports, at the front and rear respectively, with two exhaust ports located on either side of the two pairs of transfer ports; the incoming streams of mixture spread out like a fan, are deflected downward and expel the spent gases.

Reverse flush:: Cleaning the cooling system by pumping a powerful cleaning agent through the system in a direction opposite to that of normal flow.

Reverse gear:: A very low gear for driving backwards, denoted by the letter "R" on a gear knob or gear selector.

Reverse idler gear:: A gear used in the transmission to produce a reverse rotation of the transmission output shaft.

Reverse inhibitor valve:: A valve which prevents the engagement of the reverse clutch in an automatic transmissions if the vehicle road speed exceeds 10 kph (6 mph).

Reverse lock:: A steering condition where the front wheels are pointed in the opposite (reverse) direction of the turn. This technique is used in a rear wheel skid.

Reverse process:: An immersion or combined spray/immersion process employed to apply two protective coatings which, in the case of body shells, replace the dip primer coat and the filler coat. The designation derives from the fact that the sequence in which the dip primer coat and the filler coat are applied is reversed. Compare electrostatic powder coating.

Reverse scavenging:: See loop scavenging.

Reverse shoe:: See:
trailing shoe

Reverse thread:: A common name for left-hand thread

Reversible gear puller:: A puller with two or more reversible jaws, allowing it to be used for inside and outside pulling.

Reversing light:: A British term for back-up light.

Reversing valve:: Device used to reverse direction of the refrigerant flow, depending upon whether heating or cooling is desired.

Reversing warning signal:: British term for backup alarm.

Reversion:: Excessive heating of a cured rubber compound leading to deterioration of its physical properties.

Rev limiter:: See engine speed limiter.

Revolution counter:

A tachometer, which measures the engine speed in rpm.
A counter which counts the total revolutions of a shaft as opposed to rpm.

Revolutions per kilometer:: (RPK) A measurement of the number of times a tire turns in one kilometer of travel.

Revolutions per mile:: (RPM) A measurement of the number of times a tire turns in one mile of travel.

Revolutions per minute:: (RPM) The speed the engine crankshaft is turning. Also see RPM.

Rev range:: Automotive jargon for the range of speeds (expressed as revolutions per minute) in which an engine is designed to operate. The lowest point in the rev range is the idle speed; the highest point is the redline.

Revs:

To increase the speed of an engine.
The number of revolutions per minute.

Also See:
high revs
peak revs

Revving:: See free-revving.

Reynolds numbers:: A numerical ratio of the dynamic forces of mass flow to the sheer stress due to viscosity.

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