Despite its traditional appearance, a truck tyre is so much more than just simply a circle of vulcanized rubber. The numerous high-performance composites of a truck tyre are constructed from multiple materials and are one of the most complex ancillary components of a truck. The proportion of the materials used to create a tyre (including rubber, fillers and other components) depends on the desired performance goals expected from a particular tyre.
Once the tyre compounds have been mixed, they are then cut or extruded into profiled individual components after which the tyre is constructed from the inside outwards. From there onwards, the tyres are cured to provide their desired and final shape, including the tread pattern and sidewall markings. All tyres undergo a complete tactile inspection, X-Ray and Uniformity check before warehousing and subsequent sale into the market.
Chris Westland, technical specialist at Apollo Tyres explains how truck tyres are constructed, ultimately ensuring premium performance delivery.
Tread: A tyre’s tread is the part that comes into direct contact with the road surface and provides the traction required to manoeuvre the vehicle. The design of the tread depends on the axle position and application type. The tread base and cushion are located directly under the layer of tread cap compound and help to minimise the tyre’s temperature.
Working belts: A series of steel belts below the tread base serve a number of purposes, helping to stabilise the tread, reduce distortion when the tyre is moving over the ground, provide resistance to punctures, and enhance the tyre’s structural integrity.
Belt edge filler: At the ends of the working belts on a tyre you will find rubber skim, designed to reduce the forces acting on the belt ends when a tyre is in use.
Shoulder cushion: Shoulder cushions are contoured rubber strips found on the body ply under the belt ends. They help provide belt contouring and insulate the body ply from the belt edges.
Bead bundle: Bead bundles form a high-strength unit allowing an inflated tyre to fit perfectly on a wheel rim. Made by winding high-tensile wires insulated in rubber, they act as a tyre’s anchor, ensuring it remains in place on the rim and resists any pull forces.
Apex: A rubber profile located above the bead bundle is called the soft apex. It provides a smooth transition from the stiff bead area to the flexible sidewall.
Sidewall: The sidewall helps increase comfort and lateral stability. The surface of the sidewall is marked with information regarding the load and speed capabilities, maximum inflation pressure, and brand/product name.
Body ply: The body ply gives a tyre its structural strength, its ability to contain air pressure, its deflection characteristics, and provides sidewall impact resistance. These plies transmit all load, driving, braking and steering forces between the wheel and tyre tread.
Innerliner: The innerliner has very low permeability, preventing the diffusion of air and moisture through the structure of the tyre.
Rim strip: The rubber layer between the body ply and wheel rim is known as the rim strip. It is in direct contact with the wheel rim and is designed to withstand mounting and demounting.
Chafer: The strip of wire placed around the body ply cord in the bead area is called the chafer. Its purpose is to protect the bead area from damage during mounting and demounting and reduce the effects of chafing between the wheel and tyre bead.
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