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Gripping stuff - what makes a tyre?

Tyre
Cyclist magazine
13 Jun 2016

There's a lot more in your tyres than just air...

It doesn’t matter what you ride or where you ride it, staying rubber-side down is crucial. And whether that rubber is in tubular, clincher or tubeless form, there’s more going on beneath your tread than meets the tarmac.

In the hunt for the holy triumvirate of speed, grip and durability, most tyre manufacturers follow the same basic formula: a carcass (1), made from woven strands of cotton or nylon and impregnated with a rubber compound, forms the body of the tyre, onto which the tread (2) is attached. In the case of clincher tyres such as this Continental Gatorskin, a Kevlar bead (3) is folded into the edges of the carcass, which keeps the tyre ‘round’ when inflated while gripping the internal walls of a wheel rim without blowing off under pressure. 

Depending on the tyre, a puncture-resistant layer known as a breaker strip (4) can be inserted between the carcass and the tread. In the case of the Gatorskin, puncture resistance is increased by what Continental terms a ‘DuraSkin’ layer (5), a cut-resistant mesh that extends from bead to bead.

Unlike tubular and open tubular tyres, where the tread is glued onto the carcass, clincher tyres are vulcanised. This process involves the addition of an accelerator or curative chemical (such as sulphur or a peroxide) to the tyre’s rubber mix or compound. When heat and pressure are applied the parts bond together as the polymer chains in the compound cross-link, forming a more robust substance.

Each rubber compound will differ depending on the manufacturer. Such ‘recipes’ are closely guarded, but as a rule involve a mixture of natural rubber, synthesised rubber and carbon black – a soot-like substance derived from burning gas or oil that helps increase durability and lends tyres their black colour in the process (natural rubber is white).

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