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BigO Tire

Suspension & Front End

Tire Terms


Aspect Ratio

The ratio between tire height and width.


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.


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.


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


The structure of tire cords locked around wire beads.


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


Circumferential channels between the tread ribs of a tire.


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.

Low Profile

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

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.


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.


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).


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.


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.


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.

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