Cars - http://maxpages.com/carsinhistory/R

Rim offset: A measurement in inches from the center of the rim (between the flanges) to the tip of the 28° gutter bevel.

Rim pull: Actual amount of effort in pounds available at the point of contact of tire and road surface.

Rim strip: !!!.

Rim tape: !!!.

Rim taper: The slope of the rim. See advancedrimtaper semi-drop center rim taper, drop center rim taper, flatbase rim taper, and intermediate rim taper.

Ring: A circular piece or band of metal. See balk ring, chainring, chrome ring, compression ring, flywheel ring gear, lockring, oil control ring, oil ring, o-ring, piston ring, piston ring, chrome, piston ring, compression, piston ring end gap, piston ring expander, piston ring groove, piston ring job, piston ring, pinned, piston ring ridge, piston ring side clearance, ring and pinion, ringbolt, ring gear, slip ring, and snap ring.
Ring and pinion: A term used to describe the differential drive pinion and ring gear. Also see final drive ratio.

Ringbolt: An iron bolt having a ring through an eye at one end, through which a rope can be passed and tied.

Ring, chrome: See piston ring, chrome.

Ring, compression: See piston ring, compression.

Ring end gap: See piston ring end gap.

Ring expander: See piston ring expander.

Ring gap: See piston ring end gap.
Ring gear: 1. The large bevel, circular gear which is attached to the flange or carrier of the differential case. It meshes with the drive pinion on the end of the propeller shaft. 2. The outer gear in a planetary gearset. Also see flywheel ring gear.

Ring groove: See piston ring groove.

Ring job: See piston ring job.

Ring, pinned: See piston ring, pinned.

Ring ridge: See piston ring ridge.

Rings: See piston ring.

Ring side clearance: See piston ring side clearance.

Rising rate suspension: See rising-rate suspension.

Rising-rate suspension: A suspension system where the spring rate increases when the wheels move further into jounce. This action can be accomplished by configuring the geometric shape of the suspension, by using springs which change tension as they are compressed, or by using two or more springs with rubber stops. The purpose of a rising-rate suspension is to maintain consistent ride and handling characteristics under a variety of situations: loaded or unloaded, straight roads or curves, and smooth roads or bumpy.

Riser: See heat riser.

Rivet: A metal pin used to hold two objects together. One end of the pin has a head and the other end must be set or peened over to create another head.

RL: Refers to red line tires which were marketed in the late '60s and early 70s.

RMA: Acronym for "Rubber Manufactures Association"

Road course: !!!.

Road feel: The feeling imparted to the steering wheel by the wheels of a vehicle in motion. This feeling can be very important in sensing and predetermining vehicle steering response.

Road hazard: Injury to a tire sustained in normal operation, excluding collision or vandalism and that is not reparable by accepted standards.

Roadholding: The ability of a vehicle to grip the pavement. Technically described as "lateral acceleration," because cornering is actually a continuous deviation from a straight path. Measured in g's.

Road load horsepower: The amount of power at the driving wheels needed to move a vehicle down the road at a steady speed. This power varies according to the vehicle's speed, aerodynamic drag, mechanical friction, and the tires' rolling resistance. Road-load horsepower is distinct from engine power because the output of the engine is sapped by various mechanical losses between the engine's output at its flywheel and the driving wheels.

Road rash: !!!.

Roadster: (Rdstr) An open-type body with one cross seat and a luggage compartment in the rear deck. The weatherproof fabric top may be folded, and side curtains may be removed. The windshield usually may be folded down. Also see sport roadster.

Roamer: The 1925 8-88, 6-54e, 4-75; 1926 4-75e and 8-88; 1927; 1928; 1929 8-88; 1929 8-125; and 1930 8:125 models are classic cars.

Robertson screw:.

Rochet-Schneider: The 1925-1948 models with required application are classic cars.

Rocker arm: A curved lever that pivots in the middle. One end is attached to the top of the valve stem. In overhead-valve engines the other end is attached to the push rod. In some overhead-cam engines the other end is attached directly to the camshaft lobe. As the camshaft rotates, the rocker arms pivot causing the valves to open and close. Also see ball joint rocker arm and high lift rocker arms.

Rocker arm cover: A metal lid located on top of the cylinder head on vehicles that have valves that are activated by an overhead cam or by rocker arms. See valve cover.

Rocker arm shaft: The shaft upon which the rocker arms are mounted.

Rocker panel: That section of the vehicle body between the front and rear fenders and beneath the doors.

Rockwell hardness: A measurement of the degree of hardness of a given substance.

Rod: 1. A modified car. Also see street rod. 2. To drive a vehicle hard. 3. A connecting rod. See connecting rod, boxed rod, and throwing a rod. 4. To clean out a radiator by passing a rod through the lines. See rodding the radiator. 5. A thin bar. See boxed rod, metering rod, panhard rod, push rod, radius rods, tie rod, TV rod, and arc welding.

Rod bearing: See big-end bearing.

Rodding the radiator: The top and sometimes, the bottom tank of the radiator is removed. The core is then cleaned by passing a cleaning rod down through the tubes. This is done when radiators are quite clogged with rust, scale, and various mineral deposits.

Rohr: The 1925-1948 models are classic cars.

Roll: The motion of a vehicle in which the springs on one side of the vehicle compress while the springs on the other side extend. If the roll is extensive, the vehicle will fall on its side. Also less accurately called "sway" or "lean," it occurs in corners because the car's center of gravity is almost always higher than the axis about which it rotates. Also see anti-roll bar, rollbar, roll cage, roll center, roll steer, roll stiffness.

Roll cage: A protective structure which surrounds the driver in the event of a rollover or crash. It includes a rollbar and other bars welded to the rollbar. The roll cage also adds chassis strength and stiffness which makes for better handling characteristics.

Roll center: A term which is used to describe the point around which the body of the vehicle rolls when it corners. If the movement of the vehicle is controlled only by linkages, the roll center can be discovered by the geometry of the suspension.

Roll-off: See tire roll-off.

Roll pin: See spiral wrapped pin.

Roll resistance: See roll stiffness.

Roll steer: A characteristic of handling which gives a slight improvement to steering as the suspension moves in body roll. Sometimes a bad roll steer occurs when the suspension is poorly designed.

Roll stiffness: The turning moment or torque that the suspension makes when the body rolls and the suspension tries to pull the body back to its normal upright position. It is usually measured in lb-ft/degree of roll. When the springs are stiffer or when the perpendicular distance from the springs to the roll center is greater then the roll stiffness increases. As a result, the vehicle corners flatter. Also called roll resistance.

Rollbar: A heavy steel bar or tubular steel that goes from one side of the frame, up and around in back of the driver in a hoop, and back down to the other side of the frame. It is used to protect the driver in the event his vehicle rolls over.

Roller: 1. A device for replacing sliding friction with rolling friction. 2. While ball bearings use a series of balls in a cage, roller bearings use a series of small cylinders. Also see worm and roller.

Roller bearing: A bearing using a series of straight, cupped, or tapered rollers engaging an inner and outer ring or race. Also see tapered roller bearing.

Rollercam brake: See rollercam brakes.

Rollercam brakes: mountain bike brakes that are attached to the frame posts and use a cam and pulley system to modify pressure on the rims.

Roller clutch: A clutch, using a series of rollers placed in ramps, that will provide drive power in one direction but will slip or freewheel in the other direction.

Roller lifter: See roller tappets.

Roller lifters: See roller tappets.

Roller tappet: See roller tappets.

Roller tappets: valve lifters that have a roller placed on the end contacting the camshaft. This is done to reduce friction between the lobe and lifter. They are generally used when special camshafts and high tension valve springs have been installed. Also called "roller lifters."

Rollers: A stationary training device that consists of a boxlike frame and three rotating cylinders (one for a bike's front wheel and two for its rear wheel) on which the bicycle is balanced and ridden.

Rolling radius: The distance from the center of the tire's ground contact patch to the center of the wheel rim.

Rolling resistance: As the wheels begin to turn, there are forces which resist its motion such as low tire pressure, rough road surface, increased tire temperature, tire composition, and increased vehicle weight.

Rolling start: !!!.

Rolls-Royce: The 1925-1948 models are classic cars. All the 1947-67 models are milestone cars.

Roll steer: A steering effect induced by load transference from side to side. The axles may move out of their normal parallel relationship due to spring deflection.

Romeo: See Alfa Romeo.

RON: Acronym for "Research Octane Number" see octane number.

Roof pillars: !!!.

Rotary engine: An internal combustion engine which is not of a reciprocating (piston) engine design. There is no true crankshaft, although the power-take-off shaft is sometimes called the crankshaft. It is stationary or fixed in that it simply spins in place. The central rotor turns in one direction only and yet produces the required intake, compression, firing and exhaust strokes. Because it uses rotary motion instead of reciprocating motion, the rotary engine has better balance and less vibration than piston engines. Two common rotary engines are the gas turbine and the Wankel.

Rotary flow: The movement of the oil as it is carried around by the pump and turbine in a torque converter. The rotary motion is not caused by the oil passing through the pump, to turbine, to stator, etc., as is the case with vortex flow. Rotary flow is at right angles to the center line of the converter whereas vortex flow is parallel (more or less depending on the ratio between the speeds of the pump and turbine).

Rotate tires: See tire rotation.

Rotation: See tire rotation.

Rotator: See valve rotator.

Rotax: !!!.

Rotor: 1. A small rotating cap-like unit at the end of the distributor shaft. It is located on the breaker cam inside the cap. It connects between the center electrode and the various outer spark plug terminals as it turns, thus distributing the high voltage from the ignition coil secondary winding to the proper spark plug. 2. A rotating armature inside a stator. As the rotor turns within the stator, electricity is produced to power the electrical components. 3. A trichoidal device in a rotary engine.

Rotor pump: !!!.

Rotovalve: See Thompson rotovalve.

Roughing stone: A coarse stone used for quick removal of material during honing.

Roundel: See BMW roundel.

RPK: Acronym for "revolutions per kilometer" in measuring the number of times a tire turns in one kilometer of travel.

RPM: 1. Acronym for "revolutions per minute." A tachometer measures engine revolutions in terms of rpm. Also see engine speed and red line. 2. Acronym for "revolutions per mile" in measuring the number of times a tire turns in one mile of travel.

RS: 1. Acronym for "Rally Sport"; a term used to identify some Chevrolet Camaro models. 2. Acronym for "rumble seat."

RTV: Acronym for "Room Temperature Vulcanizing" sealant.

Rubber: 1. All the rubber seals, mats, and pads that cushion and protect vehicle windows, trim, handles, bumper sections, carpets, etc. 2. The tires. See also peel rubber. 3. An elastic substance used in tires. Also see butyl, natural rubber, and synthetic rubber.

Rubber-isolated crossmember: A laterally aligned structural member that is attached to the body or the frame via vibration-absorbing rubber isolators. By bolting suspension or driveline components to such crossmembers, automotive engineers can reduce the transmission of noise and/or ride harshness to the body.

Rubbing block: A little block located on the movable point that contacts the distributor cam wheel and causes the points to open. A spring causes the points to close.

Rubbing compound: A polish that contains abrasives harsh enough to remove layers of "dead" paint. Useful in radical restoration procedures, rubbing compounds should not be used on new cars or those with delicate finishes.

Rumble: 1. A noise found in high-compression engines and associated with bending vibration of the crankshaft. It is caused by abnormally high rates of pressure rise near top dead center. 2. A vibration caused by loose components. Also see rumble seat.

Rumble seat: (RS) An open-air seat at the back of some older automobiles. Called a "dickey" in Britain.

Runabout: An open sporting-type vehicle, lightweight, with two seats and with simple bodywork.

Run flat: Damage sustained by a tire due to driving with insufficient air pressure or while flat. Some types of tires will allow you to run the tire with no air pressure for a short period of time.

Run in: See break-in.

Run-in: See break-in.

Running board: A long flat footboard on either side of a vehicle which acts as a step for passengers. They were particular common on vehicles before 1940.

Running fit: See running-fit.

Running-fit: A fit in which sufficient clearance has been provided to enable the parts to turn freely and to receive lubrication.

Running gear: The system of the engine, transmission, drive shaft, differential, and wheels.

Running on rails: !!!.

Run on: Condition when the engine continues to run, even when the key is turned off. See dieseling.

Runout: The amount a gear or wheel moves in and out away from its true center as it is rotated. If runout is excessive the gear or wheel can be seen to wobble as it rotates. Also see vacuum runout point.

Ruxton: The 1925-1948 models are classic cars.

RWL: Acronym for "raised white letter," as in rwl tires..

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Page Updated Sun May 20, 2001 8:08pm EDT