A type of steering system that uses a small gear (pinion) to move a linear gear (rack) horizontally. The tie rods are attached to either side of the rack, eliminating a number of components used in a conventional worm-gear steering system.
Tire construction utilizing plies whose cords run radially from bead to bead under the tire’s tread. The advantages are more flexible side walls with a relatively stiff tread area and a larger and more consistent footprint on the road under all driving conditions.
The engine's heat exchanger. Coolant circulating around the engine’s cylinders and through the cylinder head, carries engine combustion heat to the radiator, where it is released to the atmosphere, thereby reducing the temperature of coolant. (See “COOLING SYSTEM”)
REAR WHEEL DRIVE
Drivetrain configuration that drives only the rear wheels.
REAR WINDOW DEFROSTER
A defrosting or de-misting system that typically uses thin wires embedded in the vehicles rear glass to remove mist or frost. The system’s wires heat-up, thereby heating the glass slightly to help evaporate moisture on the surface and improve visibility.
A chemical compound, typically gas or liquefied gas (R-12 and R-134), used in air conditioning systems to help produce cool air.
A secondary muffler, often used to generate a desired exhaust note or further quiet a vehicle’s exhaust system.
ROLLER ROCKER (ARM)
A type of rocker arm used in an engine’s valve train to open/close intake and exhaust valves. A roller rocker uses a roller bearing at the end that makes contact with the engine’s valves to reduce wear and increase performance.
As a vehicle’s wheels begin to turn, there are forces which resist its motion (rolling resistance) such as low tire pressure, rough road surface, increased tire temperature, tire composition, and increased vehicle weight.
RON (RESEARCH OCTANE NUMBER)
A fuel’s numeric octane rating. Most common are 87 (unleaded regular), 89 (unleaded, middle grade) and 92 (unleaded premium). (See “OCTANE”).
An auxiliary cargo area on a vehicle’s roof, typically used on wagons and SUV’s, the racks feature fixed roof side rails and adjustable cross rails to secure cargo.
ROOF SIDE RAILS
(See “ROOF RACK” above)
Roof pillars or roof posts are formed metal structures that provide support for a vehicle’s roof. Typically, vehicles have an “A” Pillar for the forward roof support located near the windshield; a “B” Pillar for the center or second roof support normally between the front and rear doors, and the “C” Pillar - located behind the rear door opening near the rear window. Wagons and SUV’s may also have a “D” Pillar at the rear corners of the vehicle.
ROTARY TYPE CLIMATE CONTROLS
Climate controls that use rotary knobs rather than levers or buttons to control climate system functions.
In a disc brake system, the disc rotates on the axle and incorporates both attachment for the wheel and a braking surface contained in the brake caliper. (See “DISC BRAKE”)
Revolutions Per Minute - a measure of the number of revolutions an engine’s crankshaft completes per minute. The tachometer on a vehicle’s dash measures RPM’s. (See “TACHOMETER”.)