Visit to the Michelin factory in Vitoria

Manufacturing a tyre is not easy and involves the most rigorous quality control. This is what we were able to learn (among other things) during the visit to the Michelin factory in Vitoria, the second oldest and the only one of the 4 in Spain producing civil engineering tyres.

Everything begins with a study of the components that will make up the tyre. The rubber, as the main component, is reinforced with fabrics of different materials to achieve high strength and excellent firmness and elasticity against the pressures they must withstand, mainly from vehicles of large dimensions that can reach 600 tonnes in weight.

A tyre, as one might think, does not consist of using rubber (or its derivatives) in an elastic state, injecting it into the mould and finishing. Everything begins with the selection of different metallic and synthetic materials that vary even within the same sizes to offer maximum flexibility, strength and grip in any situation.

Each properly treated material, ready to be assembled, is sent along the production line, where a drum passes through several stages (more than 10) and each of the materials is added. These are arranged automatically, one on top of another, forming layers that are rigorously checked in a process lasting just 14 seconds from the placement of the first layer to the last, not counting the tread.

The first step is to fit a synthetic rubber element impermeable to air, which for some years has replaced the inner tube. A textile cord ply (radial carcass) is then placed. On the sides of the tyres, two metal beads are formed to provide the necessary rigidity, which are wrapped by the carcass ply. Next, other plastic elements are added, including the specific material for the sidewalls (the flanks), which must provide both rigidity and elasticity. Finally, it is inflated from the central part, so that what was previously a cylinder gradually takes on the shape of the tyre that we all know.

Before the tread, two plies with metal wires arranged diagonally are placed. Strength is now very high to prevent deformation. It is time to place the band that will be in contact with the ground. It is a completely malleable and very delicate material, as it is raw and must be subjected to extremely high temperatures and pressures. Curing, although it varies between different tyres, takes around 10 minutes. A membrane filled with hot water at high pressure pushes the component against the walls of the mould, vulcanising the rubber and shaping the profile, geometry and final properties of the tyre.

The last step before storage and distribution is to check that the whole process has been carried out correctly. Real specialists verify each tyre produced, one by one. They subject them to continuous rotation, mainly by hand, to confirm that their rotation is symmetrical and perfect. It is one of the most important phases in tyre production, and watching them at work is truly astonishing.

For large-size tyres the process is slightly different, although the steps are very similar. Due to size and weight, it is not as automated, and what were previously drums and stages of 1-2 seconds are now static stations with 2 people taking around 12 hours to form all the layers of the tyre. Curing large tyres with the same technology goes from taking a few minutes to up to 12 hours, although the ovens are not in operation the whole time, as the residual heat they contain completes the internal vulcanisation process. The verification of rotation and condition is not carried out manually; instead, they are subjected to ultrasound to verify their correct manufacturing process and final quality.

The Vitoria factory is the second oldest in Spain, followed by the Lasarte factory, which this year celebrates its 75th anniversary. Over 3,000 employees work in Vitoria (almost a third of the total across Spain and Portugal), and total Spanish production reaches 400,000 tonnes a year, a figure that places the brand in the premium category among tyre manufacturers.

In Vitoria, tyres of very varied sizes are produced. Passenger car tyres are made in sizes of 14, 15 and 16 inches, with more than 120 different sizes. In civil engineering they make fewer size varieties, but equally spectacular ones that reach more than 5,000 kilos and 4 metres in diameter. The factory can proudly say that in 1995 it manufactured the heaviest tyre in the world to date (Guinness World Record), reaching 5,725 kilos in weight.

According to the heads of the manufacturing process who assured us, each manufacturer chooses the compounds it wants for each of its models, and each tyre is made exclusively for each car model. It is the brand’s specialists who verify that the tyre is perfectly made for that particular car, so that maximum performance of both can be obtained. We, the rest of mortals, are not able to notice this difference, so we must make sure to fit a tyre of the same dimensions as those listed in the car’s technical data sheet.

Finally, drivers should be made aware that the tyre is the only point of contact of the car with the road, and that it must always be in excellent condition to deliver its maximum performance. Following the manufacturer’s advice and staying within the law is a driver’s obligation.