Glossary of Tire Terms

ASPECT RATIO: An expression representing the height of the sidewall of a tire in terms of a percentage of tire's width.

ASYMMETRIC: When opposite sides of a tire's tread pattern are not identical.

COMPOUND: The general term referring to the chemical formula for the tread material.

GROOVES: Circumferential channels between the tread ribs of a tire.

HIGH PERFORMANCE TIRE: In the tire industry, those tires with speed ratings of S or greater and aspect ratios of 70 or less. 2.

HYDROPLANING: Loss of traction at high speeds caused by a wedge of water that lifts a tire off the road surface.

TRUCK TIRES: Tires designed for off-the-road and on/ off-the-road use on sport/utility, small commercial, and recreational vehicles.

LOAD RATING: A method of rating a tire's load-carrying capacity (denoted by letters such as B, C, D, etc.) with respect to its ply rating.

LOW-PROFILE: A term describing a tire with a low relative aspect ratio or series classification.

METRIC TIRE SIZE SYSTEM: A tire sizing system using the section width (mm), aspect ratio, speed category, tire construction, and the rim diameter (inches). Example: 185/70SR13.

P-METRIC SYSTEM: A tire sizing system using the section width (mm), aspect ratio, type of tire construction, and rim diameter (inches). Example: P225/70R15.

PASSENGER CAR TIRE: Automobile tires featuring aspect ratios of 70 or greater, using a taller profile for increased ride comfort.

PLY: A layer of rubber-coated fabric or wire making up the tire casing.

RADIAL TIRE: A tire built with casing plies that cross the crown at an angle of 90 degrees.

RIBS: Parts of a tire tread pattern created by grooves that run circumferentially around the tire.

SERIES: A numerical representation of a tire's aspect ratio; for example, 50 series.

STEEL BELT: A belt material used in radial tires. Its high stiffness provides good handling and low treadwear.

TIRE PROFILE: A term representing the portion of a tire measured as its aspect ratio or series.

TOURING PERFORMANCE TIRE: A tire providing the ride comfort of a passenger car tire, yet possessing high performance tire characteristics.

UTQG: Uniform Tire Quality Grade. A government-mandated tire rating system based on a tire's performance in treadwear durability, traction, and temperature resistance. UTQG ratings are branded on a tire's sidewall.

Z-SPEED OR Z-PERFORMANCE RATED: A speed category for tires with a maximum speed capability of 149+ MPH.
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