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.
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.