How a tyre is created


Before describing process performance, the production phases involved in creation of a tyre are described here. There are two principal phases:

XX production of the rubber compounds used in the various components of the tyre: tread, sidewalls, liner, bead filler, etc.

XX construction of the base structure, an actual rubber “framework” that supports all the components.

The rubber part of the tyre (tread, sides and fabric) is a special mix, more commonly referred to as a “compound,” which is mainly composed of rubber (both natural and synthetic), plasticizers (petroleum derivatives) and binders (mainly carbon black and silica).

The sum of these components represents about 90% of the compound, with the remaining 10% or so being accounted for by other components with specific functions (e.g. accelerating agents, anti-decomposition agents, vulcanizing agents...).

The plasticizers, carbon black, and silica are stored in dedicated silos and sent to a closed mixer (“banbury”), in which the compound undergoes initial processing. A computer controls and manages the quantities, both for the ingredients from the silos and for the various ingredients that compose the compound.

During the second phase of mixing, special chemicals – vulcanizing agents and accelerants – necessary for the subsequent phases are added to an open mixer consisting of two big rollers.

Then, the compound sheet is plunged into a vat (“batchoff”) for final cooling. At this point, the compound is ready and used to fabricate the tyre tread or other components of the tyre. It is then extruded into the appropriate form for the subsequent steps.

The heart of the tyre structure is represented by the fabrics, which are formed by longitudinal threads (weft) and may be comprised of various materials. The fabrics are then cut at a certain angle with respect to the longitudinal direction (the direction of movement, of rolling or of the weft).

Other key parts of the tyre are the tread and the sidewall. The first of these performs critical functions, such as stopping on dry and wet surfaces. The second is the area close to the metal rim, which is called the “bead.” The base of the bead is supported by the ring, comprised of a series of steel wires, which stiffens the part touching the wheel rim.

The components described thus far must be assembled together to make the finished tyre.

This assembly process is carried out by using devices that are called “building machines.”

The resulting tyre (called a “raw tyre”) is then sent to be vulcanized, which involves a genuine solid state chemical reaction. After being cooled, the vulcanized tyre is deburred to remove any imperfections that might alter its appearance. Then it undergoes an initial visual inspection (both internal and external, to check that there are no obvious fabrication defects), which is then followed – in the case of truck tyres – by an X-ray inspection in specially shielded areas.

The birth of a tyre

Come nasce un pneumatico

Source: Science and Technology of Rubber, 2nd edition, Academic Press