Tire Glossary



A

Air pressure

The amount of air inside the tire pressing outward on each square inch of tire, which is expressed in pounds per square inch (psi) or kiloPascals (kPa), the metric designation for air pressure.
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Airtight Synthetic Rubber

Formulated with virtually impermeable butyl rubber, this material replaces the inner tube in modern, tubeless tires. Check you air pressure monthly, as some air loss occurs over time.
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Alignment

When all wheels on the vehicle are adjusted so that they are pointed in the optimum direction relative to the road and each other.
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All-season high-performance tires

Tires that deliver a measure of traction on snow and ice without sacrificing dry performance driving capabilities.
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All-season tires

Tires that provide a good balance of traction in rain or snow with good tread life and a comfortable, quiet ride.
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All-season traction

Indicates the tire’s ability to provide a balance of traction in wet, dry, and winter conditions.
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APS

An advanced silica-based winter rubber compound that helps provide flexibility where the tread surface makes contact with the road.
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Aquaplaning

An extremely dangerous situation where water builds up in front of the tires resulting in the tires losing contact with the road surface. At this point, the vehicle is skimming on the water surface and is completely out of control. Also called hydroplaning.
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Aramid

A synthetic fabric used in some tires that is (pound-for-pound) stronger than steel.
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Aspect Ratio

The relationship of a tire’s sidewall height to its section width.
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Asymmetrical Tread Design (AD)

Different tread patterns featured on either side of the tread that enhance and optimize performance for both wet and dry handling. The inside shoulder has more grooves for water evacuation and massive tread blocks on the outside shoulder make for maximum handling.
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B

Balance/Imbalance

The state in which a tire and wheel spin with all their weight distributed equally. To correct an imbalance, a trained mechanic will add weights on the interior or exterior of the wheel.
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Banded At Zero Technology

Michelin®BAZ Technology uses spiral-wrapped nylon strips applied in the tread area atop the steel belts at zero degrees. BAZ Technology opposes centripetal forces that can cause tire distortion at high speeds1. BAZ Technology optimizes high-speed handling and durability.
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Bead

The section of the tire that sits on the wheel. Inside, there is a round hoop of steel wires, wrapped or reinforced by body ply cords, that clamps the tire firmly against the wheel rim.
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Bead Chafer

A key component of the tire that is the contact point between the tire and the wheel, designed to withstand forces the wheel puts on the tire during mounting as well as the dynamic forces of driving and braking.
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Bead Filler

Responsible for transferring propulsion and braking torque from the wheel rim to the road surface contact area.
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Bead Tension Structure

Two sidewall plies wrapped around each bead wire in opposite directions providing lateral stability but flex to absorb road irregularities.
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Belt

A rubber-coated layer of cords that is located between the body plies and the tread. Cords are most commonly made from steel but may also be made from fiberglass, rayon, nylon, polyester or other fabrics.
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Bias-Ply

A type of tire with crossed layers of ply cord running diagonally to the center line of the tread.
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Bolt Circle

The diameter of an imaginary circle drawn through the center of each lug nut hole and then measured from two holes that are directly across from each other. The measurement is used in selecting the proper wheel for replacement.
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Braking Torque

A technique practiced by drag racers and road testers to improve their off-the-line acceleration; applying the brake and throttle at the same time, increasing the engine rpm until release of the brake.
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Breakaway

A term used to describe a loss of traction when negotiating a curve or when accelerating from a standing start. The tires slide against, instead of grip, the road surface.
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C

C3M Technology

A manufacturing process that permits precise placement of different tire components and multiple rubber tread compounds.
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Camber

A wheel’s inward or outward tilt from vertical, measured in degrees. The camber angle is adjusted to keep the outside tires flat on the ground during a turn.
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Camber Thrust

Side or lateral force generated when a tire rolls with camber, which can add to or subtract from the side force a tire generates.
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Carbon Black

This is a reinforcing filler which, when incorporated into the tire rubber compound, gives it a high resistance to wear.
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Carcass

The supporting structure of the tire consisting of plies anchored to the bead on one side and running in a radius to the other side and anchoring to the bead. Also called casing.
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Carcass Ply

Made up of thin textile fiber cables bonded into the rubber. These cables are largely responsible for determining the strength of the tire.
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Carrying Capacity

At a given air pressure, how much weight each tire is designed to carry. For each tire size, there is a load inflation table to ensure the inflation pressure used is sufficient for the vehicle axle load.
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Caster

The angle between a line drawn vertically through a wheel’s centerline and the axis around which the wheel is steered; improves a car’s directional stability and on-center feel.
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Centerline

An imaginary line down the center of the vehicle. Alignment tracking is measured from this line.
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Centrifugal Force

The sideways acceleration, measured in g’s, of an object in curvilinear motion. As a car traverses a curve, centrifugal force acts on it and tries to pull it outward. To counteract this, the tires develop an equal and opposite force acting against the road. Also called lateral force.
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Cold Inflation Pressure

The amount of air pressure in a tire, measured in pounds per square inch (psi) before a tire has built up heat from driving.
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Comfort Control Technology

Uses precision manufacturing to ensure an ultra-high level of tire uniformity, while also employing powerful proprietary tread design software to minimized tread acoustics.
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Compliance Cushion

An added rubber tire component between the tread and belt that absorbs road irregularities for a smoother ride.
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Contact Patch

The area in which the tire is in contact with the road surface. Also called footprint.
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Cord

The strands of fabric forming the plies or layers of the tire. Cords may be made from polyester, rayon, nylon, fiberglass or steel.
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Cornering Force

The force on a turning vehicle’s tires - the tire’s ability to grip and resist side force - that keeps the vehicle on the desired arc.
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Cross Z-Sipes Technology

A sipe pattern that provides lateral and longitudinal stiffness within the tread block.
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Crown Plies

Provide the rigid base for the tread which allows for good fuel economy. The plies also provide centrifugal and lateral rigidity to the tire, and are designed to flex sufficiently for a comfortable ride.
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Curb Weight

Weight of a production vehicle with fluid reservoirs (including fuel tank) full and all normal equipment in place, but without driver or passengers.
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