Hot retreading Most tyres undergo hot retreading - Photo credits ©: fr.fotolia.com/rezulteo.com

By only replacing the tread, retreading is the cost-effective way to prolong tyre life. Two techniques exist to achieve this result.

Hot or cold reaction

Most tyres are retreaded with heat. After the casing is inspected and buffed, the retreader places a strip of uncured rubber on the casing. The tread/casing assembly is then placed in a heated mould where the rubber vulcanises, “bonds” to the casing and adopts its circumferential structure. This process corresponds to the production of new tyres, which explains why it is commonly used.

For cold retreading, the strip is pre-vulcanised. The tread already has its final tread pattern before it is bonded onto the casing. A bonding strip is inserted between the casing and the tread strip then the retreader places the tyre in an autoclave where the final vulcanisation effectivelybonds all of the elements together. Certain tyres, mainly “low-profile” or “budget” tyres that have been refused by hot retreaders, may be accepted for cold retreading.

Regardless of whether a tyre is retreaded by heat or cold, all tyres are subject to a final inspection to ensure that they can safely return to service. The two processes provide quality tyres, almost identical to their new equivalents.

Tyre manufacturers often differentiate between the two retreading techniques by giving them their own brand specific names. For example, Continental calls its heat retreaded tyres ContiRe and its cold retreaded tyres ContiTread, where Michelin talk about Remix and Recamic.

By Renaud Lacroix

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