# Time to learn Tire Terms

## Aspect Ratio

Section height/section width x 100 – ratio between tire height and width

## Asymmetric

When 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 that are crossed over one another at an angle (on a bias) plus two reinforced belts that encircle the tires under the tread.

## Bolt Circle

Sometimes referred to as bolt pattern: The number of lug holes on the diameter of the imaginary circle that each lug hole is centered on.

## Carcass

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

## Casing

The structure of tire cords is locked around wire beads.

## Compound

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

## Criss-Cross Torquing

The recommended sequential tightening of the lug nuts in a pattern across from one another helps ensure even tightening.

## Grooves

Circumferential channels between and the tread ribs of a tire.

## Hub Centric

A situation where the center bore of the wheel is made to match up with the diameter of the automobile hubs; the wheel is then balanced by the center hold rather than the lug holes.

## Hydroplaning

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

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.

Read: WHEELS: PARTS, SIZES, BOLT PATTERNS, WHEEL OFFSET, ONE-PIECE VS TW-PIECE WHEEL AND HOW THEY MADE

## Low Profile

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

## Negative Offset

A condition where the wheel’s mounting surface is closer to the inside of the wheel; when the mounting surface is inboard the wheel’s centerline.

## Nominal Rim Diameter

Diameter of rim seat supporting the tire bead. Examples: 13′, 15″ and 16.5″.

## Offset

The positive or negative distance from the wheel’s centerline to the mounting surface of the wheel.

## Overall Diameter

The diameter of the inflated tire without any load.

## Overall Width

Maximum width in cross-section of the unloaded tire including protruding sides 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.

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 that encircle the tire under the tread.

## Ribs

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

## Rim Flange

The edge of the wheel’s rim that the clip-on weights attach to.

## Rim Width

The distance between the inside surfaces of the rim flanges.

## Section Height

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

Related Content:

## 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.

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

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

## Unsprung Weight

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

## 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 the tire’s sidewall.

## Varied-Pitch Ratio

Variations of angles and sizes of a tire’s tread elements that reduce ride noise levels.

## Zero Offset

A condition where the wheel’s mounting surface coincides with the centerline of the wheel.