The process of tyre manufacture is a complex one - there are around seven different tyre components, all needing to be constructed in a precise manner to give best performance such as reliability, longevity and road-holding. Get one element wrong, and it could be disastrous.
Most of us know the basic components of a tyre – beads, belts, ply, sipe and groove, sidewalls, shoulder and tread, but very few know how a tyre is constructed. Just what are the processes involved?
Blend of ingredients
There are up to thirty ‘ingredients’ in any one tyre blend, dependent on what the tyre is for – a hard-wearing truck tyre won’t have the same blend as a high performance tyre for example. As these blends are proprietary and key to any tyre manufacturers success, you won’t find a list of them on the internet.
Typically, a tyre construction uses several different rubber compounds, compromising both natural and synthetic rubber, a number of ‘fillers’ such as carbon black and silica, and few other ingredients which varies per construction (although some of these are chemical compounds).
It’s the compounds that add the unique properties – ultra-high grip for example. These ingredients are all mixed together and heated, the result of which is a black, sticky rubber compound. From this point, the rubber is left to cool before heading to the next construction step.
Tyre milling
The mill is used to shape the rubber into strips, usually by rolling the rubber compound out before cutting. It’s these strips that form the basic construction of the tyre.
Other elements are also prepared in this process, such as the sidewalls and beads. Although some of these elements have added processes, such as the inclusion of steel belts or wire bundles, they also have extra rubber added, dependent on the tyre component.
Once the ‘plies’ have been constructed, it’s time to piece it all together in the build area.
Building the tyre
Generally, the tyre is built up from the inside out, although some manufacturers do it differently, but the process is similar. The strips of rubber are laid into a tyre building machine; the different strips are called plies and there are usually around four per regular car tyre. It’s here that the other elements are also brought together.
Essentially, the plies are laid into the machine, glued together and then the sidewalls and beads are added. The internal drum of the machine expands under steam pressure, which has two effects – the first being to force the tyre against the outer part of the machine, and the second is that the steam heats the rubber to help the moulding process.
Once the tyre has been built, it’s left to cool down before being released, this product is known as a ‘green tyre’ – it’s recognisably a tyre, but just not ready for the road until it’s been cured.
Tyre curing
The nature of the tyre changes the exact process for curing, but typically, the tyre is placed in a curing press, which heats the tyre again and allows the external markings (including tread blocks and manufacturers markings) to be stamped in to the tyre. The result is the final tyre that’s ready to be fitted to a car. In theory, you could do just that, but most manufacturers will give the finished tyre a final inspection.
Although strictly not part of the actual building process, the final inspection is vital to the quality and safety of the tyre – a tyre is the only connection between your vehicle and the road, so any flaws could be a potential safety issue on the road.
Most tyre manufacturers have specialist inspectors that take each tyre and thoroughly inspect it by eye before passing it off. They’re looking for any flaws or blemishes that could be a potential weak spot, and on each production run, a number of finished tyres will be pulled from the production line for x-ray inspection – ensuring uniform thickness and quality.
The making of tyres
When you understand how tyres are produced, it’s quite easy to see why they aren’t cheaper – especially when you consider the job that they do. Too many people are happy to skimp on the cost of tyres, but a quality tyre can change your whole driving experience in terms of ride quality, handling, performance (including braking) and longevity.
When you understand how tyres are produced, it’s quite easy to see why they aren’t cheaper – especially when you consider the job that they do. Too many people are happy to skimp on the cost of tyres, but a quality tyre can change your whole driving experience in terms of ride quality, handling, performance (including braking) and longevity.
A tyre isn’t just a lump of rubber that’s been moulded in a machine, there’s countless hours of design, manufacturing and build in each and every one. It’s for this reason that we have ultimate grip in wet weather, lower fuel costs, shorter braking distances and, overall, better ride quality. It could be argued that the tyre is one of the most developed parts of the modern car.