Glossary of Terms

wrenchheader1Not everyone who wants to know more about cars is a gearhead, and even those that have spent a lifetime in automotive pursuits occasionally see words or terms with which they are unfamiliar. Indeed, I have been told that sometimes the verbiage used in this blog is over the heads of some readers. To help resolve this, readers can refer to this page for a description and/or definition of any word or term that might be outside of standard vernacular. If you see such a word or term anywhere in this blog (or anywhere, really; I’m happy to define any automotive terminology), post a comment here or in the article where it appears and I will add it to this section. ~Chris

Air filter – The paper or cloth filtering element that keeps your engine from sucking damaging debris into the combustion chamber.

Autocross (Auto-x) – A motor-sports event in which drivers attempt to navigate a course, constructed of traffic cones, in as little time as possible. One driver goes at a time, so victory is determined by lap time only—no wheel-to-wheel racing occurs. Vehicles are classified according to their speed and handling capabilities so that driving skill is emphasized over equipment. For more info see the SCCA page for Solo racing.

Brakes, Disc – The stopping system in which a spinning brake rotor is squeezed by two brake pads to create the friction necessary to slow the vehicle. See this article for more info.

Brakes, Drum – The stopping system in which shoe-shaped pieces of friction material are forced outward against the inside of a drum-shaped hub. Much less efficient than disc brakes, but much cheaper. See this article for more info.

Chassis – Although this can have several definitions, as I use it, it refers to the basic frame of a car.

Contact patch – the portion of a tire that is actually in contact with the ground.

Heat cycling – A process in which the tread area of a high-performance tire is heated and cooled in a cycle so that the chemical bonds in the rubber are broken and then reformed, reinforcing their strength. Results in better grip at high temperatures and longer tire life. See this Tire Rack article for further info.

Lift – A large piece of machinery that raises a car off the ground for easier access to the under side.

Tire sizing – The correct way to read a tire size, xxx/yyRzz: x represents the tire’s tread width, in millimeters; y represents the height, which is a percentage of the width (it is also called the ‘aspect ratio’); R stands for ‘radial,’ which is the standard design for all modern tires; z represents the size wheel the tire fits. Thus, a tire with the size 185/60R13 is 185mm wide, the height is 60% of that width, and it will fit a 13-inch wheel.

Tread – The outer portion of a tire, that comes into contact with the road. The tread must provide grip to move a car forward and guide it through turns, as well as direct water, snow and other debris away so that the driver can maintain control.