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

Aspect Ratio: An expression representing the height of the sidewall of a tyre in terms of a percentage of tyre's width.

Asymmetric: When opposite sides of a tyre's tread pattern are not identical.

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

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

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

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

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

Chafer: A finishing strip of calendered fabric used to protect the tyre'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 and inner portion of the sidewall. Also used in enlarged form to stiffen the lower sidewall of a tyre.

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

H-Speed or H-Performance Rated: A speed category for tyres with a maximum speed capability of 200 km/h.

High Performance Tyre: 1. In the tyre industry, those tyres with speed ratings of S or greater and aspect ratios of 70 or less. 2. At YOKOHAMA, those tyres with an aspect ratio of 70 or less and a speed rating of H, V or Z.

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

Light Truck Tyres: Tyres 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 tyre'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 tyre with a low relative aspect ratio or series classification.

Metric Tyre Size System: A tyre sizing system using the section width (mm), aspect ratio, speed category, tyre construction and the rim diameter (inches). Example: 185/70SR13.

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

Passenger Car Tyre: Automobile tyres 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 tyre casing.

Radial Tyre: A tyre built with casing plies that cross the crown at an angle of 90 degrees.

Ribs: Parts of a tyre tread pattern created by grooves that run circumferentially around the tyre.

S-speed or S-performance rated: A speed category for tyres with a maximum speed capability of 180 km/h.

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

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

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

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

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

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

Tire Profile: A term representing the portion of a tyre measured as its aspect ratio or series.

Touring Performance Tyre: A tyre providing the ride comfort of a passenger car tyre, yet possessing high performance tyre 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 tyre.

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

V-Speed or V-Performance Rated: A speed category for tyres with a maximum speed capability of 240 km/h.

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

Z-Speed or Z-Performance Rated: A speed category for tyres with a maximum speed capability of 240+ km/h.