A Big O Tires Technician Helps You Learn to Speak 'Tire'!

Aspect Ratio
The ratio between tire height and width.

Asymmetric
A tread pattern in which opposite sides of a tire’s tread pattern are not identical.

Backside Setting
The distance from the mounting surface of the wheel, which contacts the hub, to the back rim flange. It is sometimes referred to as the backspacing or backside measurement.

Balance
The even distribution of weight on a mounted wheel and tire.

Bias-Belted Tire
A passenger type tire which has two rubberized plies of cords which are crossed over one another at an angle (on a bias) plus two reinforced belts which encircle the tires under the tread.

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

Carcass
The portion of a tire that is the foundation for the tread, belts, bead and sidewall.

Casing
The structure of tire cords locked around wire beads.

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

Grooves
Circumferential channels between the tread ribs of a tire.

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

Load Rating
The maximum weight that the tire is designed to carry; dictated by the tire's construction. Metric passenger type tires are offered with a Standard Load Rating (up to 35 psi), or Extra Load Rating (up to 41 psi). LT Metric (truck type) tires are offered with ply ratings of C (8 ply), D (8 ply), and (10 ply) and at various inflation pressures up to 80 psi.

Nominal Ring Diameter
Diameter of rim seat supporting the tire bead. Examples: 13", 15" and 16.5".

Overall Diameter
The diameter of the inflated tire without any load.

Overall Width
Maximum width in cross-section of the unloaded tire including protruding side ribs and decorations.

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

Positive Offset
A condition where the wheel's mounting surface is closer to the street side of the wheel; when the mounting surface is outboard the wheel's centerline.

Radial Ply Tire
A type of tire that has one or more rubberized plies of cords running from bead to bead (at right angles to the tread and parallel to each other), plus two or more plies of reinforced belts which encircle the tire under the tread.

Ribs
Part of a tire tread pattern created by grooves that run circumferentially around the tire.

Section Height
The distance from rim seat to outer tread surface of an unloaded tire.

Section Width
The linear distance between the outside sidewalls of an inflated tire without any load (exclusive of protruding side ribs and decorations).

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 and low treadwear.

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

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

Tread Width
The portion of the tread design that comes in contact with the road.

Unsprung Weight
The total weight of the automobile's components not supported by the suspension system; wheels and tires are prime examples.

UTQG
The UTQG is a 'user-friendly' way for consumers to understand basic tire specs. It stands for Uniform Tire Quality Grade. It's a government-mandated tire rating system based on a tire's performance in treadwear durability, traction and temperature resistance. UTQG ratings are branded on the tire's sidewall.

Varied Pitch Ratio
Variations of angles and sizes of a tire's tread elements that reduce ride noise levels.

Low Profile
A term describing a tire with a low relative aspect ratio or series classification (short sidewall, wide tread).