The first step is to mix up the rubber itself. While different bits of the tyre use varying compounds, they all share the same building blocks of natural rubber (from a tree!), synthetic rubber and various additives. These include sulphur, which makes the rubber tougher when heated (‘vulcanised’), and carbon black, which adds durability.
The carcass is the body of the tyre. It’s made by coating cotton cloth in a layer of rubber to form a sheet. This is then cut diagonally, before being rejoined end to end. The beads of the tyre (the lower edges, which hook into the rim) are made in a similar way, by coating either steel wire or twisted Kevlar strands in rubber.
The carcass is then mounted on a drum. Using lasers to ensure accuracy, the beads are put in place and the carcass is folded over them. Strips of rubber, often of different compounds (eg. harder in the centre for fast rolling, softer on the shoulders for grip) are then laid on top as the drum is spun, before being cut to length and joined. These will form the tread.
Next, the logos are placed on the tyre. As with the rest of the manufacturing process, at Hutchinson this is done by hand. Because it requires so much dexterity to do this accurately and quickly, most of the workers are female. Apparently men are too clumsy! On the plus side, this ensures high demand for new tyres.
The tyre is now one step away from being ready. It’s sprayed with a release agent and then placed into a heated mould. Here, an expanding bladder presses the rubber that was applied in step 3 into a pattern on the mould that adds the knobs, sipes (small incisions) and chamfers (sloped edges) that create grip on the trail.
The heat causes a chemical reaction that changes the rubber mixture from soft and squidgy into a much more durable form. When the mould opens, the final product is just a quality check away from being ready to ship to shops and hit the trails. Next time you bemoan the price of new tyres, think about all the work that goes into your rubber!