Basic Tyre Information

Variety of tyre – Categories of the tyre types

Functions of Tyres – 4 Important Functions of Tyres

Tyre construction

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Tread

The tread is the part of a tyre that contacts the road surface.
the tread consist of a layer of rubber, compounded to suit the application purpose of the tyre, and the thickness serves to protect the belt and carcass. Depending on application a suitable tread pattern is moulded at the time of curing. The tread pattern serves the purpose of improving water drainage, providing traction, braking and cornering characteristics and aiding in NVH performance.

Shoulder

The shoulder on each side of the tread is designed to protect the belt and carcass of the tyre and to disspate heat generated during running to the atmosphere.

Belt

The belt is a reinforcement layer extending around the outer circumference of the carcass under the tread. It acts like an iron hoop in improving the stiffness of the tread area.

Bead filler

This is a reinforcement rubber that has a triangular cross-section and which is used to increase the stiffness of the bead.

Bead wire

A ring-shaped reinforcement material that is made by bundling together several steel wires.

Inner liner

The inner liner is a layer of special rubber that has high resistance to air migration.

Carcass

The carcass is the load-bearing framework that forms the body of the tyre. It is composed of rubber coated fabric laid in a radial direction. The carcass contains the inflation pressure aiding in supporting the load and absorbing impact.

Bead

The bead area supports the extremities of the carcass on each side of the tyre. This is the part of the tyre that anchors the tyre to the wheel.

Side wall

The sidewall on each side of the tyre, between the shoulder and the bead is the section that deflects most during running. The rubber coating serves to protect the carcass.

Tyre dimensions

The picture shows where the tyre is measured for the tyre size code.

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Total width

The exterior measurement of a tyre’s width from inner to outer sidewall (including protective ribs and decorations) when properly mounted and inflated.

Section width(W)

The exterior measurement of a tyre’s width from sidewall to sidewall (excluding protective ribs or decorations) when properly mounted and inflated, but with no load placed upon the tyre.

Section height(H)

The measurement of the vertical distance between the tyre’s bead seat and outer tread surface when properly mounted and inflated, but with no load placed on the tyre.

Inside diameter (Rim diameter)

The linear distance between bead seats measured at the widest point. This measurement may be in inches or millimeters.

Outside diameter

The linear distance between the tyre’s tread surfaces measured at the widest point. This measurement is taken with the tyre mounted on the measuring rim and no load applied.

Tyre dimensions

Load Index(LI)

The capacity of each tyre in withstanding the load is referred to as the load capacity. The load index is a numerical code associated with the maximum load a tyre can support.

Speed Symbol

The SPEED SYMBOL indicates the maximum speed at which the tyre can carry a load corresponding to its Load Index under service conditions specified by the tyre manufacturer. (except for speeds above 210km/h, see the above section, “Load capacities and speed limits” respectively for Passenger Cars)

Aspect Ratio

Aspect ratio is the section height expressed as a percentage
of the section width (e.x. 70, 65, 60, etc.).