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How is a tyre made?
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How is a tyre made?

27.07.2020

The production of a MICHELIN premium tyre is a science in itself. Including the raw materials, it consists of around 200 materials. The structure is highly complex, the materials used are high-tech at its finest and the production processes interlock with millimetre and second precision.

A car tyre is round, black and made of rubber. Quite simple. But if you take a closer look, you will see that the structure of a modern MICHELIN radial tyre is incredibly complex. Thanks to many measures, Michelin has reduced energy consumption during production by up to 20 percent in recent years. The use of new high-tech materials has even reduced the consumption of raw materials by an average of one third. Whereas a tyre weighed twelve kilograms ten years ago, today it weighs only eight kilograms. Moreover, it is more durable and has better driving characteristics than its predecessors.

A look at the five steps of tyre production shows how highly complex the production of a MICHELIN premium tyre is:

First preliminary stage

High-quality raw materials are processed in precisely calculated compositions to create important composite materials, known as compounds

The raw materials include:

  • Natural rubber: it ensures that the tyre remains largely flexible even at low temperatures.
  • Natural and synthetic elastomers: Together with other components, they improve a tyre's resistance to wear and ageing as well as its grip.
  • Fillers such as carbon black and silica compounds (a group of minerals): Michelin was the first tyre manufacturer to use silica back in 1995.
  • Steel: used to make the steel belt and wire cores.
  • Textiles: textile cords are the backbone of the tyre.

Then there are oils and waxes. They protect the finished product against environmental influences such as ozone, UV rays and oxidation. Sulphur ensures the optimal bonding of the carbon black molecules during vulcanisation (step 4), where it performs a similar task to that of yeast in baking a cake. Modern MICHELIN tyres can contain up to 16 different rubber compounds.

Second preliminary stage

Production of tyre components

  • Textile cord for the carcass ply(s) and for special belt plies of passenger car tyres. Steel cord for the carcass ply(s) of light truck and truck tyres as well as for the main belt plies of all tyre types.
  • The bead core, together with the shape of the bead, ensures that the tyre sits firmly on the rim thanks to the air pressure. MICHELIN uses only round cores for its passenger car tyres.
  • Tread: Extruders form an endless profiled strip from the rubber material produced in a mixing plant, which is cut to the correct length according to the tyre size.
  • Sidewall: Sidewall sections cut to the tyre size are produced by the extruder in the same way as the tread.
  • Inner layer: The airtight inner layer (butyl) is formed into a wide, thin layer by a calender or extruder.
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Steel cords give the tyre its strength and ensure, among other things, improved dimensional and driving stability.

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Extruders form an endless strip from the rubber material produced in a mixing plant to produce the tread.

 

The tyre structure

Assembling the tyre casing

The actual tyre production takes place on a cylindrical drum. The layers and components described above are gradually placed on it and rolled tight. In technical jargon, this is called "tyre winding". This process takes place in two phases: first the carcass and then the belt and tread. Tyre wrapping requires the highest precision and is therefore considered the most difficult production step.

 

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The carcass is the supporting structure of the tyre. Its manufacture requires extreme precision.

The vulcanisation (cooking)

In order to give the tyre its final shape, tread and finished appearance, the casing is put under high pressure at around 160 °Celsius to a state that allows it to flow into the  pattern of the cooking mould. The casing now becomes elastic. For energy-saving reasons, cooking is increasingly done electrically and not exclusively with water and steam as in the past. This process varies from ten minutes to several hours, depending on the tyre size and type. The tyre is then removed from the mould and slowly cooled.

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The curing process begins. The tyre gets its final shape after it has been vulcanised, i.e. cooked, for a certain time at a certain pressure and temperature.

The final test

Michelin subjects every single step of production, from the testing of raw materials to the moment a tyre leaves the factory, to continuous quality control.

Without exception, every tyre is inspected visually, or with optical control systems, as well as by touch. In addition, random tyre samples are taken and subjected to further tests: For example, an X-ray or ultrasound examination, a tyre uniformity test, or shearography, which detects the smallest trapped air bubbles. Only when all the tests and inspections have been completed satisfactorily does a tyre leave the factory and goes on sale or to the end consumer.

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    David Johnson

    PR Manager, Michelin UK and Ireland

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