Yokohama Tire Glossary

Aramid: A synthetic fiber that is, per weight, stronger than steel. Used in tire construction & provides excellent high tensile strength to weight.

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.

Block Design: A tire tread pattern made of raised rubber- compound segments.

Blocks: The individual, raised rubber-compound segments making up the tread of a tire.

Buckling: A condition when a tire is bulging or crumpling.

Carcass: That portion of a tire that is the foundation for the tread, belts, bead & sidewall.

Casing: The structure of tire cords locked around wire beads.

Chafer: A finishing strip of calendered fabric used to protect the tire's bead area from the rim.

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

Drive Wheel(s): The wheel(s) that provide the power or driving force for a vehicle.

Filler: The material used to fill the area above the bead between the outer & inner portion of the sidewall. Also used in enlarged form to stiffen the lower sidewall of a tire.

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

H-Speed or H-Performance Rated: A speed category for tires with a maximum speed capability of 130 MPH.

High Performance Tire: 1. In the tire industry, those tires with speed ratings of S or greater & aspect ratios of 70 or less. 2. At Yokohama, those tires with an aspect ratio of 70 or less & a speed rating of H, V or Z.

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

Light Truck Tires: Tires designed for off-the-road & on/off-the-road use on sport/utility, small commercial & 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 & 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 & 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.

S-speed or S-performance rated: A speed category for tires with a maximum speed capability of 112 MPH.

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

Shoulder Blocks: Raised rubber-compound segments on the part of the tire tread nearest the sidewall.

Sipes: Slits in the tire tread. Small cuts in the surface of the tread to improve traction.

Steel Belt: A belt material used in radial tires. Its high stiffness provides good handling & low treadwear.

Steer Wheel(s): The wheel(s) that direct the course of a vehicle.

Stud Holes: Small cavities along a tire's tread designed to hold tire studs for increased traction on snow-covered surfaces.

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.

Trailer Wheel(s): The wheel(s) of a trailer unit that neither provide power nor direct the course of a vehicle.

Tread Blocks: Raised rubber-compound segments on the outside visible part of a tire.

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

V-Speed or V-Performance Rated: A speed category for tires with a maximum speed capability of 149 MPH.

Varied-Pitch Ratio: Variations in angles & sizes of a tire's tread elements that reduce ride noise levels.

Z-Speed or Z-Performance Rated: A speed category for tires with a maximum speed capability of 149+ MPH.