Dictionary of Automotive Terms Abbreviations

DICTIONARY OF AUTOMOTIVE TERMS - "Ra"

R

Letter designation for tires to indicate that they are Radial as in P185R13 tire. See Speed rating.
Reverse.
A letter on a fuel gauge indicating low fuel; when first illuminated it indicates that there is approximately five litres left in reserve.
Symbol for Resistance

R-11: (trichloromonofluoromethane) Low pressure, synthetic chemical refrigerant which is also used as a cleaning fluid.

R-12: (dichlorodifluoromethane) Popular refrigerant known as Freon 12.

R-22: (monochlorodifluoromethane) Low temperature refrigerant with boiling point of -41 0F (-40.50C( at atmospheric pressure.

R-113: (trichlorotrifluoroethane) Synthetic chemical refrigerant which is nontoxic and nonflammable.

R-160: (ethyl chloride) Toxic refrigerant now seldom used.

R-170: (ethane) Low temperature application refrigerant.

R-290: (propane) Low temperature application refrigerant.

R-500: Refrigerant which is an azeotropic mixture of R-12 and R-152a.

R-502: Refrigerant which is azeotropic mixture of R-22 and R-115.

R-503: Refrigerant which is azeotropic mixture of R-23 and R-13.

R-504: Refrigerant which is azeotropic mixture of R-32 and R-115.

R-600: (butane) Low-temperature application refrigerant; also used as a fuel.

R-611: (methyl formate) Low pressure refrigerant.

R-717: (ammonia) Popular refrigerant for industrial refrigerating systems; also a popular absorption system refrigerant.

RABS: Acronym for Rear-wheel Anti-lock Brake System (Ford)

RAC: Acronym for the Royal Automobile Club.

Race

Bearing Race

The inner or outer ring that provides a contact surface for the balls or Rollers in a bearing.
A competition (usually based on Speed) between two vehicles.
To run an engine at high speed when not in gear.

Also See
Drag race
Race camshaft Bearing race

Race cam: A type of camshaft for race car engines which increases lift of valve, speed of valve opening and closing, length of time valve is held open, etc. Also called Full cam, Three-quarter cam, or Semi-race cam, depending upon design.

Race camshaft: A Camshaft, other than stock, designed to improve engine performance by altering Cam profile. Provides increased lift, faster opening and closing, earlier opening and later closing, etc. Race camshafts are available as semi-race or street grind, Three-quarter race camshaft or full race. Grinds in between these general categories are also available.

Racer: See
Boy racer
Cafe racer

Racing: See
Banger racing.

Racing Green: See
British Racing Green.

Racing harness: See
4-point racing harness.

Racing start: A start on a normal street, e.g., at traffic lights, using excessive throttle resulting in wheelspin and screeching tires.

Rack: A long, toothed bar.

Also See
Ache rack
Head ache rack
Luggage rack
Roof rack
Steering rack
Trunk rack

Rack and pinion: See
Rack and pinion gearbox.

Rack and pinion gearbox: Rack and pinion gearbox

A type of Steering system with a Pinion gear on the end of the Steering shaft. The pinion engages a long rack (a bar with a row of teeth cut along one edge). When the Steering wheel is turned, the pinion turns and moves the rack to the left or right. This movement is carried through Tie rods to the Steering arms at the wheels.

Rack and pinion steering: Rack and pinion steering

The pinion gear rotates with the steering shaft, moving the rack from side to side. Several full turns of the pinion are required to shift the rack from lock to lock. Because there are so few parts in the steering linkage, rack and pinion is a very precise and responsive steering system and is often used in sports cars.
Also See
Rack and pinion gearbox

Rack-and-pinion steering: See
Rack and pinion steering

Rack galvanizing: A galvanizing method for objects which can be placed on a rack.

Rad: Abbreviation for Radiator.

RAD: Acronym for radiator temperature switch

Radar detector: A device which will sense the presence of a radar device which law enforcement officers might be using to spot speeders.

Radial: See
Radial engine
Radial tire

Radial bearing: A bearing designed to absorb the radial forces acting on a pump. Compare Thrust bearing

Radial clearance: See
Radial play.

Radial commutator: Electrical contact surface on a rotor which is perpendicular or at right angles to the shaft center line.

Radial compressor: A compressor with pistons radiating out from the centerline of the compressor. The Harrison (Frigidaire) is a typical example.

Radial cooling fins: Brake drum cooling fins that are parallel to the centerline of the axle.

Radial cracking: Cracking of sidewall rubber running perpendicular to the tire beads. May result from underinflation or exposure to ozone.

Radial discharge nozzle: Booster venturi with four spokes or arms which carry fuel to the outer circumference of the booster before discharging it from tiny holes in the ends of the spokes. Used only on the Corvair Model H carburetor.

Radial engine: Radial Engine

An internal combustion engine with a number of Cylinders arranged in a circle around the Crankshaft center line. As the crankshaft turns, the pistons are in various stages of the strokes (i.e., intake, exhaust, compression, power). A design often used for aircraft engines.

Radial-flow pump: Radial-flow pump

An end-suction centrifugal pump with the liquid flowing perpendicular to the pump shaft. The liquid enters at the center of the impeller and is directed out along the impeller blades in a direction at right angles to the pump shaft.

Radial load: A load perpendicularly applied to the axis of rotation.

Radial play: A bearing clearance in the radial direction.

Radial ply: Radial ply

The ply or plies used in tire in which the cords run at right angles to the bead and parallel to the tire radius. See Radial tire.

Radial runout

A tire assembly that does not form a true circle; the radii of the circle are not equal. Most usual causes are bent wheel (out of round) or tire not mounted properly (beads not seated). This is one of the main causes of vehicle vibration.
A variation in the diameter of a brake disc, wheel, or tire from a specified amount.

Radial shaft seal: A typical seal design used to prevent leaks between stationary parts and rotating shafts and to exclude foreign matter. A lip seal, typically of neoprene, is held in a metal retainer and applies a sealing pressure to a rotating shaft, the pressure being provided by an annular garter spring winch surrounds the sealing lip; radial shaft seals are used wherever a shaft penetrates a casing, such as on crankshafts, camshafts, water pump shafts, etc.

Radial tire: Radial tire

A type of tire construction which has the main carcass Plies or cords which run at right angles to the bead and parallel to the radius. By itself, this construction is very weak because when the Bias angle is smaller, the structure is stiff. However, the radial tire has a very large Bias angle. In order to strengthen the tire, a belt surrounds the circumference. This belt is made of low-angle plies (usually about 15 degrees). In this way, the Tread area is stiff and the Sidewalls are flexible. In this way the sidewalls can act independently of each other. In a P185/80R13 tire, R indicates a radial tire.
Also See
Steel belted radial tire

Radiant barrier: A thin, reflective foil sheet that exhibits low radiant energy transmission and under certain conditions can block radiant heat transfer; installed in attics to reduce heat flow through a roof assembly into the living space.

Radiant drier: See
Infrared radiant drier.

Radiant energy: Energy that transmits away from its source in all directions.

Radiant heating: Heating system in which warm or hot surfaces are used to radiate heat into the space to be conditioned.

Radiation

Radiator

The transfer of heat from one object to another when the hotter object sends out invisible rays or waves that upon striking the colder object, cause it to vibrate and thus heat.
The process by which energy (such as heat) is emitted by one body, as particles or waves, transmitted through an intervening medium or space (like air), and absorbed by another body. Also refers to the energy transferred by this process
The transfer of heat through matter or space by means of electromagnetic waves.

Also See
Thermal radiation

Radiation shield: A separate panel or panels interposed between surfaces and jackets to reduce heat losses through radiation.

Radiative forcing: A change in average net radiation at the top of the troposphere (known as the tropopause) because of a change in either incoming solar or exiting infrared radiation. A positive radiative forcing tends on average to warm the earth's surface; a negative radiative forcing on average tends to cool the earth's surface. Greenhouse gases, when emitted into the atmosphere, trap infrared energy radiated from the earth's surface and therefore tend to produce positive radiative forcing. Also see Greenhouse gases.

Radiatively active gases: Gases that absorb incoming solar radiation or outgoing infrared radiation, affecting the vertical temperature profile of the atmosphere. Also see Radiative forcing above.

Radiator: A device that cools the liquid in the Cooling system by allowing it to circulate through a series of water Channels, which are exposed to air Ducts.
Also See
Crossflow radiator
Downflow radiator
Heat exchanger
Pressure radiator cap
Rodding the radiator

Radiator cap

Pressure cap

A Pressure cap at the top of the radiator.
A high pressure cap used in radiators to allow operation at high temperature. Higher pressure raises the boiling point of the coolant.

Also See
Pressure radiator cap.

Radiator drain cock: Radiator drain cock

A radiator tap; unlike the Radiator drain plug, tools are not required to drain the coolant from a radiator with a drain cock.

Radiator drain plug: A threaded closure plug located at the underside of a radiator used to drain the coolant; usually equipped with a hex or Allen head.

Radiator fan: Two types are used on automobiles a crankshaft-driven fan connected by a temperature-sensitive viscous coupling, or a fan driven by an electric motor.

Radiator fan motor: An electrically operated motor responsible for driving the radiator fan. An electric motor allows much more freedom in radiator location and engine bay design and permits aftercooling of the engine with the engine switched off most engines mounted crosswise at the front (as on most front-wheel-drive subcompacts) use electric radiator fans which also lead to reduced power losses, since the vehicle's engine is not also required to drive the radiator fan also. The problem with them, however, is that even with the engine off, the fan may start up unexpectedly for the person inspecting the engine bay.

Radiator fill hole: An opening at the top of the Radiator through which new water and Coolant can be added when the engine and radiator is cool. In modern vehicles, an overflow reservoir is the location for topping off the radiator fluid since opening a hot radiator cap can be dangerous. The Pressure cap seals the fill hole.

Radiator grille: The grating that admits cooling air to the radiator.

Radiator grille surround: The sheet metal panel for mounting the radiator grille; often combined with the front apron to form a single front panel.

Radiator guard: See
Side radiator guard.

Radiator hose: The rubber pipe connecting the radiator to the cylinder block.

Radiator hose shark tooth pliers: A special automotive tool for removing and installing radiator and heater hoses; round and toothed jaws securely grip the hose while the handles provide leverage to twist the hose free.

Radiator overflow tank: Radiator overflow tank

A small bottle that acts as a reservoir for liquid expelled from the Cooling system through the Overflow pipe and returns the liquid to the system when it cools down. A special Radiator Pressure cap is also part of the kit. It is also called a Closed Cooling System when it is part of the Original equipment.

Radiator pressure cap: See
Pressure cap.

Radiator shell: Radiator shell

A metal or plastic enclosure which surrounds the outside perimeter of the radiator and mounts to the frame of the vehicle. In modern motorcycles, it is usually chromed.

Radiator support panel: A panel located behind the radiator grille surround which provides a mounting for the radiator and connects the mudguard skirts at their front edge.

Radiator tank: A reservoir containing the coolant in a radiator. Early units were made from sheet metal, typically brass or aluminum. Newer versions used advanced polymer technology and injection molding processes have made it possible to produce radiator tanks from thermoplastics. Since all modern cars use forced circulation systems, there is no need for a vertical flow through the radiator. Thus most radiators are mounted horizontally. Also called Radiator Overflow Tank

Radii adapter: A mounting device that is used to center a drum or rotor on the arbor of a lathe. A radii adapter centers the drum or rotor through contact with the bearing races.

Radio: A device which receives radio signals (either AM, FM, or both) and plays the sound through the speakers. Automobile radios began to appear in vehicles in 1928. Even in the mid-1960s, many cars came without radios.

Also See
Car radio
Cb radio
Citizens band radio
Din radio
Mobile two-way radio

Radio/cassette deck: (r/c) A combined radio and tape deck.

Radio choke: An electric coil used to prevent static in the radio caused by opening and closing of the contact points in the instrument voltage regulator.

Radio Data System: (RDS) A system which interrupts a radio broadcast with the latest information on e.g., traffic problems.

Radio frequency interference: (RFI) interference generated by the ignition system and other electrical apparatus; counteracted by suppressors.

Radiograph: A photograph obtained by passing X-rays or gamma rays through the object to be photographed and recording the variations in density on a photographic film.

Radius: See
Buffered radius
Crown radius
Free radius
Loaded radius
Radius rods
Rolling radius
Scrub radius
Static loaded radius
Turning radius
Unloaded radius

Radius arm: An additional suspension link in a beam axle layout providing fore-and-aft location of the axle.

Radius rod: An additional suspension link in a beam axle layout providing fore-and-aft location of the axle.

Radius rods: Rods or arms which are part of the Suspension, usually a live rear axle. They are attached to the axle and pivoted on the Frame. They are used to keep the axle at right angles to the Frame (i.e., prevent lateral movement) and yet permit an up and down motion. On some cars like the Triumph Spitfire, they are used to help locate the Swing axles.

Radius seat: A spherical seat that provides positive centering of the wheel bolt head in the wheel.

Radon: A naturally occurring radioactive gas found in the United States in nearly all types of soil, rock, and water. It can migrate into most buildings. Studies have linked high concentrations of radon to lung cancer.

RAF: Acronym for Reactivity Adjustment Factor

Rag: See
Tack rag.

Rage: See
Road rage.

Ragtop: Colloquial term for Convertible.

RAI: Acronym for Nederlandse vereniging de Rijwiel-en-Automobiel Indusrie (Netherlands).

Rail

A Dragster built around a relatively long pipe Frame. The only body panels used are around the Driver's cockpit area.
A common pressure accumulator.

Also See
Common Rail Injection Drip rail
Fender rail
Fuel rail
Oil rail
Roof rail
Running on rails
Seat rail
Shift rail
Shift rails
Side rail

Rail console: See
Seat rail console.

Rail job: A vehicle that has been transformed into a dragster built around a long pipe frame with minimal body panels.

Railroad locomotive: Self-propelled vehicle that runs on rails and is used for moving railroad cars.

Rails: See
Running on rails
Shift rails

Rail, shift: See
Shift rails.

Railton: A vehicle brand of which the 1925-1948 models, with required application, are Classic cars.

Rain: See
Acid rain.

Rain grooves: Channels cut into a road's surface to help water run off the road during a rainstorm

Raising: The action of beating a rounded shape out of a flat panel by starting in the center and working outward in a spiral to the edge; the metal is shrunk around the edge but remains about the same in the center.

Rake

The angle at which a rod is attached. Also see Fork rake.
The fore-and-aft inclination from the vertical.

Raked: A vehicle which has the Ground clearance or body altered so that either the front or rear of the vehicle is increased or lowered, thus giving the vehicle a tilted appearance.

Rake the leaves: Trucker slang for the last vehicle in a string as in "Looks like I get to rake the leaves tonight."

RAM: Acronym for Random Access Memory -- memory that serves as a temporary storage place for data from the sensors.

Ram air

In a ram air system, carburetors get fresh air to be mixed with the gasoline via forward facing ducts. The idea is that as the vehicle moves faster, more air is forced or rammed into the carburetors resulting in improved performance.
A term referring to the air forced through the condenser coils by vehicle movement or fan action.

Ram induction: Using the forward Momentum of vehicle to scoop air and force it into Carburetor via a suitable passageway.

Ram intake manifold: An Intake manifold that has very long passageways that at certain Speeds aid the entrance of fuel mixture into the Cylinders.

Ramp

Equipment used to support a vehicle's front or rear for underbody work.
A device used to raise a vehicle in the air.

Ramp-over angle: An indication of how high a hump the vehicle can negotiate without scraping the undercarriage or becoming high-centered; that is, stuck with the center of the vehicle on the hump and the wheels in the air.

Ram pressure: The pressure generated by the deflection of the fluid flow due to the curvature of the stator blades, resulting in a momentum acting on the turbine.

Ram tube: A tube of a specific length and shape in the intake manifold that promotes performance at certain engine speeds by ramming air into the cylinders.

R&D: Acronym for Research & Development.

Random access memory: (RAM) A type of volatile memory that is used to store information for either short or long term usage. This type of memory can be written to. If energy is removed from the RAM device, the contents in memory are destroyed.

Randonnée: A long bicycle touring ride of 160 to 1200 kilometers made up of several controls (checkpoints).

Randonneur: A male long-distance cyclist. Also see the female Randonneuse.

Randonneur 5000: One of the most prestigious awards a Randonneur can earn. To be one of the recipients, a randonneur must do a full series of 200, 300, 400, 600, and 1000km Brevets, a Paris-Brest-Paris randonneur event, a Flèche team ride, and the remaining distances ridden on sanctioned brevets for a total of 5000 kilometers. The qualifying events must all be completed within a four-year period.

Randonneuring: Long distance bicycle riding within a specified length of time. First developed in France a few years before the Tour de France which later spun off from randonneuring. It is not considered a race but a ride. Everyone who completes the ride is awarded the same medal whether he/she takes the fully alloted time or not.

Randonneurs Mondiaux: An umbrella organization of national randonneuring groups. Its primary functions are to organize foreign (i.e., France, Spain, United Kingdom, Holland, Belgium, Australia, Denmark, Sweden, Norway, Finland, Austria, Germany, Russia, South Africa, Canada, and the United States) participation in Paris-Brest-Paris and other 1200-kilometer Brevets, encourage the exchange of information of interest to randonneurs, and reward clubs' and individuals' participation in long-distance randonnées with various medals and trophies.

Randonneuse

A female long-distance cyclist.
A bicycle specifically designed for randonneuring.

Range: Pressure or temperature settings of a control; change within limits.

Also See
Gear range
Heat range
Heat range reserve
High/low range gearbox
High/low range transmission
Load range
Mid-range
Product range
Rev range

Range-change: See
Auxiliary gearbox.

Range gearbox: See
High/low range gearbox.

Range gearing: See
Wide range gearing.

Range reserve: See
Heat range reserve.

Range Rover: Click image for books on
Range Rover

A model of SUV manufactured in England

Range transmission: See
High/low range transmission.

Rank: See
Taxi rank.

Rankine cycle: The thermodynamic cycle that is an ideal standard for comparing performance of heat-engines, steam power plants, steam turbines, and heat pump systems that use a condensable vapor as the working fluid. Efficiency is measured as work done divided by sensible heat supplied.

Rankine cycle engine: The Rankine cycle system uses a liquid that evaporates when heated and expands to produce work, such as turning a turbine, which when connected to a generator, produces electricity. The exhaust vapor expelled from the turbine condenses and the liquid is pumped back to the boiler to repeat the cycle. The working fluid most commonly used is water, though other liquids can also be used. Rankine cycle design is used by most commercial electric power plants. The traditional steam locomotive is also a common form of the Rankine cycle engine. The Rankine engine itself can be either a piston engine or a turbine.

Rankine scale: Name given the absolute (Fahrenheit) scale. Zero (00R) on this scale is -4600F

RAP: Acronym for Retained Access Power

Rash: See
Road rash.

Rasp

A tool like a file with coarse teeth used to prepare a tire for Section repair and for Buffing prior to Retreading.
The action of using a rasp tool.

Ratchet

A feature of a special wrench which allows you to turn the handle in one direction to tighten a nut or bolt, but turning it in the opposite direction does nothing but position the handle back where you started and leaves the wrench on the nut or bolt. Likewise you could set the wrench to loosen a nut or bolt.
A drive handle with ratchet mechanism, usually called a Socket wrench.
A toothed Rack or wheel which is engaged by a lever to permit motion in only one direction.

Also See
Air ratchet Tap ratchet

Ratchet adapter: A device which converts a torque wrench or drive handle without a ratchet mechanism into a reversible ratchet tool.

Ratchet handle: A Ratchet tool.

Ratchet jaw: Trucker slang for a non-stop talker as in "He sure was a ratchet jaw."

Ratchet screwdriver: A screwdriver with a ratchet mechanism.

Rate: See
Base interest rate
Burn rate
Charging rate
Conversion rate
Damping rate
Deflection rate
Discharge rate
Flat rate
Flat rate manual
Flow rate
Net interest rate
Progressive rate spring
Rising rate suspension
Spark rate
Spring rate
Turn-in rate

Rated capacity: The quantity of electricity which can be drawn from a fully charged battery for 20 hours by a constant discharging current until cutoff voltage of 1.75 volts per cell is reached. Compare Ampere-hour capacity.

Rated horsepower: See
SAE horsepower.

Rated power

The power output of an engine as horsepower or kilowatt.
The value stated on the generator nameplate. It is the power available at the output terminals of a component or piece of equipment that is operated in compliance with the manufacturer's performance specifications.

Rated pressure: A nominal pressure rating applied to vehicle parts.

Rated voltage: The voltage given for electrical equipment or devices which refers to specified operating conditions.

Rate manual: See
Flat rate manual.

Rate spring: See
Progressive rate spring
Single rate spring
Variable rate springs

Rates: See
Door rates.

Rate suspension: See
Rising rate suspension.

Rating: See
Amp/hr. rating
Amperage rating
Axle weight rating
Capacity rating
Cetane rating
Gross axle weight rating
Gross Combined Weight Rating
Gross Vehicle Weight Rating
Load rating
Manufacturer's performance ratings
Octane rating
Ply rating
Rated capacity
Speed rating
Tow rating

Ratio: A fixed relationship between things in number, quantity or degree. For example, if the fuel mixture contains one part of gas for fifteen parts of air, the ratio would be 15 to 1.

Also See
A/f ratio
A/f ratio
Air-fuel ratio
Air fuel ratio
Air ratio
Aspect ratio
Axle ratio
Back axle ratio
Bore-stroke ratio
Braking ratio
Compression ratio
Economy ratio
Final drive ratio
Fuel-air ratio
Fuel air ratio
Gear ratio
Overall gear ratio
Power-to-weight ratio
Power to weight ratio
Primary compression ratio
Rear axle ratio
Speed ratio
Stall torque ratio
Steering overall ratio
Steering ratio
Stoichiometric ratio

Rationalization: An industrial reorganization primarily aimed at a more cost-effective and time-saving production process.

Ratio steering: See
Variable ratio steering.

Rat-tail file: A Round file.

Rattle: See
Body rattle
Death rattle
Diesel rattle

Rattle spring: See
Spreader spring.

Rattrap: The type of Bicycle pedals that have thin metal plates with jagged edges running parallel on each side of the pedal Spindle.

RAVE valve: A device used on Two-stroke engines which automatically alters or varies the Exhaust port size. It stands for Rotax adjustable variable exhaust.

Ravigneaux planetary gear set: A system which is composed of two sun gears of different diameters, one internal gear, and several planet pinions.

Raw exhaust gas: The exhaust gas upstream of any emission control device, e.g., before it passes through a catalytic converter.

Raw rubber: Natural rubber that has not been vulcanized.

Rayleigh frequency distribution: A mathematical representation of the frequency or ratio that specific wind speeds occur within a specified time interval.

Raymond-Mays: A vehicle brand of which the 1925-1948 models with required application are Classic cars.

Rayon: A synthetic fiber.

Rays: See
Infrared rays
Ultraviolet rays