While the Ancient Greeks were first to use wheels to move things around, tyres are a much more recent development. It was only in 1839 for example that Charles Goodyear discovered vulcanised rubber, a key breakthrough in the development of the tyre.
How tyres are made today can be traced back to 1888, when John Boyd Dunlop literally reinvented the wheel. In seeking to stop headaches suffered by his son when riding his tricycle on pavements, the Scotsman wrapped a rubber tube inflated with air round the rims of the wheels. These were the first functioning pneumatic tyres.
Since then numerous advances have been made, including the invention of synthetic rubber and radial tyres. So, how are car tires made now? And, come to that, how are bike tires made?
How Tyres Are Manufactured
How are car tires made? Car tyre factories are highly automated, with machines doing the majority of the construction. There are six main steps to the manufacturing process.
- Sourcing materials
- Mixing compounds
- Manufacturing components
- Building the tyre
- Quality control
How Are Car Tyres Made? Sourcing Raw Materials
The first step in how tyres are made is sourcing the materials that make them. By far, the largest component in tyres is rubber, making up around 80% of each one. It’s this that gives tyres their elasticity and anti-slip properties. While each tyre contains numerous rubbers, these are subdivided, roughly equally, between natural and synthetic rubber. Natural rubber is sourced from plantations in tropical locations, while oil-based synthetic varieties are factory-made.
One key element of tyre manufacturing involves enhancing the rubber by making it into several compounds, which are then assembled and layered. For example, the tyre’s frame – or skeleton – is made of plies or sheets of textiles such as nylon, rayon, polyester and aramid fibre, adding to both strength and elasticity. Steel is another vital component. High-strength steel wires encased in rubber help define and retain the shape of the tyre, aids its stability and contributes to its snug wheel fit, all of which increases its mileage performance.
Among the other materials found in the rubber compounds of tyres are antioxidants, to minimise the effects of oxygen exposure, oil as a plasticiser, zinc oxide, silicone and, giving its colour, a material called carbon black.
How Tyres are Made: Mixing Rubber Compounds
Most tyres are made up of several different rubber compounds, each with a different purpose and consistency. Essentially, every part of a tyre has its own compound. To make these, the rubbers and other raw materials such as carbon black, zinc oxide, silicone and oil are added to industrial blenders in three or four stages. Two counter-rotating rotors then blend these materials together. This is a common theme in answering “how are car tyres made?”
The resulting compounds are then formed into rubber strips in a milling process. Again, this is done with dual rollers spinning in opposite directions, but this time to squeeze the rubber into shape using one smooth and one serrated roller. The result should be uniform rubber strips which are then left to cool.
How Tyres are Manufactured: Component Manufacturing
The average tyre can have anywhere between 10 and 30 components, mostly acting in a reinforcing or strengthening capacity. To make the components, various machines are used to squeeze, layer, embed, flatten and shape different elements. Machinery falls into three main categories: calendaring, extruding and beading types. All generally involve applying pressure through enormous rollers, screws, barrels and dies.
These components include:
- Ply – Providing flexibility, plies are made using textiles like rayon and nylon sandwiched between sheets of rubber compound using a calendar machine, which is basically a series of rollers that squeeze them together. Includes the radial carcass.
- Beads – Rubber coated steel hoops that connect the tyre and wheel. And steel rings are coated in rubber and encased in a rubber apex to make the steel bead, also known as the bead wire, which is what binds the tyre to the rim.
- Belt – rubber coated sheets of steel wire and cord to reinforce the tyre and maintain its shape.
- Sidewall – The extra-thick rubber side where the manufacturer’s name appears. Aids lateral stability. Steel cord is embedded into rubber to make a continuous sheet which is cut to size with the cord at a radial angle.
- Shoulder – A vital aid in taking corners, this is the grooved edge between the sidewall and tread.
- Tread – The point of contact with the road, this is the soft outer lining of the tyre. Rolls of tyre tread are made through an extrusion process involving a screw and barrel.
Every component is weighed and checked along the way.
How Tyres are Made: Assembly
Tyres are assembled layer by layer, from the inside outwards on a tyre-building machine. For this, picture a large cylindrical drum which rotates as each element is rolled on in order. The tyre build process starts with the carcass, or casing, and finishes with the tread.
First on the drum is a sheet of airtight synthetic rubber which functions as an inner liner. This is followed by the radial carcass, which underpins the tyre and will eventually be filled with air.
A pair of casing ply strips is rolled onto each end of the drum, onto which are placed the hoops of bead wires. The casing ply is folded in half over the hoops to secure them. One by one, the layers are added. The carcass is complete when the sidewalls are in place.
Next, the tyre is inflated whilst still on the tyre-building machine, the centre of the machine’s drum performing this function. Two metal reinforced rubber plies are then added, reinforcing the tyre’s shape, before the tread is rolled on as the final layer.
Only now is the unit removed from the machine. At this point, it is classed as a “green tyre”, a reference to the fact that it is almost, but not quite, complete. It’s still missing its sidewall manufacturer’s wording, grooves, and shallower markings, known as sipes.
How Tyres are Manufactured: Vulcanising
Vulcanising means treating rubber with chemicals and heat to enhance and harden it. To achieve this, the tyre is treated with a, usually sulphuric, chemical and placed inside a curing press, a machine a bit like a giant waffle (or doughnut) maker with the mould for the tyre patter along its interior circumference.
In the centre of the press is a water-heated pole. Once the green tyre is enclosed within the machine, the heat, which reaches around 170 degrees Celsius, and steam push and pressurise the external surfaces of the tyre into the outer mould. When it’s removed from the curing press, the tyre is complete.
Inspection and Testing
Each and every tyre is inspected by machine and by workers, carefully measured and assessed for uniformity as well as to check for faults. Some tyres are x-rayed, others cut open, to ensure the quality of each run. They are then tested and labelled.
How are Bike Tyres Made?
We’ve looked at cars, but how are bike tyres made? Actually, the process is remarkably similar. Just like how tyres are manufactured for cars, bike tyres are made of layers of rubberised components, most of which are the same in both cases, albeit on different scales. Even the machinery is the same, but smaller.
And there you have it. You’re up to speed on how tyres are manufactured. Now you can answer not only “how are car tyres made?” but even, how are bike tires made!