Making a Tyre

A cross section of a tyre with labelling

Having an understanding of how tyres are made is important to knowing how best to look after them, I think. So here is a brief run down of how tyres are made.

[Note: this is how it was done at Michelin when I worked for them in 2005 and it’s possible that things have changed or different manufacturers do things differently.]

The various elements that make up a tyre are put together on a large drum with a flexible part in the middle which can be inflated to form the shape of the tyre.

Firstly, the air-tight lining of the tyre is put onto the centre of the drum. A piece of rubber embedded with the casing ply (strips of textile cord in car tyres or metal cord in truck tyres) which runs from bead to bead (the metal ring that holds the tyre to the wheel) is put on top of this.

The bead wire is then put in place and the casing ply is folded over it to hold the whole tyre together. Other bits and pieces of rubber are added depending on the type and manufacturer of the tyre until the flexible sidewalls are added. Manufacturers try to make the sidewalls as durable as possible, especially in cars with low profile tyres, because there is no safe way to repair them and clipping a curb could potentially write off an expensive tyre.

With these pieces added, they inflate the centre of the drum to make the tyre tyre-shaped. Two layers of steel tread bracing ply are put along the top of the tyre to protect the inner lining from penetration and help the tread to stay flat against the road. These are laid out so they cross each other diagonally, creating tiny diamond shapes. The thick rubber of the tread is put on top of this before the whole lot goes into the mould.

Vulcanisation occurs when the rubber, which contains sulphur, is heated up. This means that the sulphur creates bonds between the polymer chains and the rubber becomes much harder and holds its shape while still being flexible. A bladder of warm water is used to push the tyre into the mould to imprint the grooves of the tread and other markings into the rubber.

So there you are.

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