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Displaying 351 - 400 of 502 glossary terms Use the search function to find terms.

Partial Zero Emission Vehicles (PZEV) are environmentally friendly automobiles that comply with strict standards.

Rack and Pinion

Rack and Pinion means a horizontal rack (= flat-toothed bar) engages a horizontal pinion on the steering column. It refers to a linear actuator that comprises a circular gear (the pinion) engaging… Read more


Radiator refers to a cooling system that works as a heat exchanger by circulating hot coolant through the engine by getting it circulated by the water pump.

Radiator Core

Radiator Core is an ahead exchange that heats the inside of the cabin. It is part of the vehicle's cooling system.

Radiator Hoses

Radiator Hoses are the flexible rubber connections between the engine radiator, radiator core, and other cooling system components.


Ratchet refers to a tool or mechanical device that allows continuous rotary or linear motion in the opposite direction.

Rear Defroster

Rear Defroster is used during winter months that melts ice or removes condensation from the rear window.

Rear Spoiler

Rear Spoilers help change airflows above, underneath, and around the vehicle. It also reduces wind resistance.


Recall refers to a safety-related bulletin that requires the vehicle to get to the dealership for modifications. The recall must be done with no charge to the consumer. Recall notices are usually… Read more


Redline is when the engine cuts off its acceleration once the maximum rpm is achieved. It is to protect the engine from several damages. The redline is usually red, or some have a red light that… Read more


Refrigerant is the chemical used in the Aircondition system of the car. It cools down the cabin if the air conditioner is activated.


Rim is the metal assembly that holds the tire and is also attached to the wheel hub.

Roll Bar

Roll Bar is tubular steel installed behind and above the driver to protect the car rolls over.

Roll Cage

Roll Cage is an application often used in race cars. It is tubular steel installed behind and above the driver to protect in case the vehicle rolls over.

Roof Rack

Roof Racks are large metal or plastic constructions that attach to a vehicle's roof and carry cargo or bicycles.

Roof Spoiler

Roof Spoiler is installed to create downforce during high speeds in high-end applications.


Roofline refers to the outline or shape of the roof.

Rotary Engine

Rotary Engine refers to an early internal combustion engine designed with an odd number of cylinders per row radial configuration. The crankshaft is still stationary in operation, with the entire… Read more


Brake Rotor, often referred to as a Brake disc, is a disc-shaped device that rotates with the wheels. Brake pads installed on a brake caliper press against it depending on the brake pedal's… Read more


Rotor or Brake Disc is the rotating part of a wheel's disc brake assembly, against which the brake pads apply. It is typically made of gray iron, a form of cast iron. Some discs are both… Read more

Rough Idle

Rough Idle refers to a vibrating and shaking engine when pressing the gas pedal.


Revolutions Per Minute (RPM) refers to the revolution per minute in which the crankshaft turns.

Run Flat

Run-flat refers to tires that can be driven temporarily after losing tire pressure.

Running Boards

Running Boards are metal boards installed on tall vehicles to aid passengers in entering tall vehicles.


Rear-Wheel Drive or RWD is a drive system that applies its motion to the rear wheels. means rear-wheel drive, a drive system that applies its motion to the rear wheels.


SAE International, or Society of Automotive Engineers, is an active association of engineers in various fields and a standard-setting organization.


Salvage is used in the automotive industry to describe a vehicle that has been damaged more than 70% of its market value. Insurance company's write off those vehicles since the repair cost is… Read more


Selective Catalytic Reduction (SCR) refers to reducing Nitrogen Oxides (NOx) in diesel exhaust.

Seat Belt Retractor

A Seat Belt Retractor refers to a mechanism the moves your seat belt out of the way when you un-buckle.

Seat belts

Seat Belts are harnesses used to secure occupants of vehicles during collisions.

Seat Extension

Seat Extension refers to a metal rail installed to the vehicle's seat to extend legroom for a very tall person.

Self-leveling Headlights

Self-leveling Headlights are adjusting to the vehicle's load the correct light settings. It is working automatically by the suspensions height sensors.


Sensors are devices that generate a signal that reports a value to the computer.

Serpentine Belt

Serpentine Belt is a ribbed belt that drives the engine's accessory. It usually drives an alternator, water pump, and air conditioner compressor. It is wrapped around several rollers and… Read more

Service Reminder Light

Service Reminder Light illuminates once the vehicle needs general maintenance.

Shift Interlock

Shift Interlock is a safety feature that prevents drivers from shifting out of the park while not pressing the brake pedal.

Shift Lock

Shift Lock may display on the dashboard reminding the driver to press the brake pedal to start the vehicle or shift it into Drive or Reverse.

Shock Absorber

Shock Absorbers or Dampers refer to a mechanical or hydraulic device designed to absorb and damp shock impulses.

Side Airbags

Side Airbags refer to small airbags that deploy during an impact to protect the passenger's ribcage.


Sidewall refers to the tire. It indicates the information about the tire size, manufacturing dates, grades, ratings, and brand.

Skid Plate

Skid Plate refers to an abrasion-resistant material that protects the underside of a vehicle or boat from damage when it makes contact with the ground. In off-road vehicles, motorcycles, and… Read more

SLS Filter

Sodium Lauryl Sulfate (SLS) Filters remove contaminants from hydraulic fluid in a self-leveling suspension system.


Sluggish means a vehicle does not accelerate smoothly.


Sequential Manual Gearbox (SMG) refers to an automated manual transmission without a clutch pedal.


Single Overhead Camshaft (SOHC) engines have a single camshaft per bank of cylinders. Dual Over Head Camshaft (DOHC, also known as "twin-cam.") engines have two camshafts per bank. The… Read more


Solenoid refers to a coil of wire used in inductors, electromagnets, antennas, valves, etc. The application of a solenoid varies in many different types of industries. It can be a simple locking… Read more

Spark Plug

Spark Plug is installed inside the cylinder head to ignite the fuel/air mixture in the combustion chamber.

Specific Gravity

Specific Gravity (SG) is a case of relative density. It defines the ratio of the density of a given substance to the density of water (H2O). Substances with a specific gravity greater than one are… Read more


Speedometers display the speed at which a vehicle is traveling.


Spoiler refers to an automotive aerodynamic device whose intended design function is to 'spoil' unfavorable air movement across the vehicle's body in motion, usually described as… Read more