Tyre manufacturing and the processes involved have come a long way since the original pneumatic tyres of the 19th century – with global manufacturers investing significantly into research and design improvements along with modernisation and the materials used.
Let’s go on a journey and see how a modern-day, advanced technology tyre gets put together and the steps and processes involved in getting it “road ready”.
RUBBER & COMPOUND
Prior to the tyre being assembled there are a number of manufacturing processes to prepare each of the ‘ingredients’ which make up the finished product — starting with the very important Rubber and Compound elements.
Rubber is used for tread and sidewall compounds and the inner liner of the tyre, which keeps the compressed air within the tyre.
There are different types of rubber, mainly synthetic and natural rubber, which when combined with fillers make up the tyre compound formulation. The types of rubber and filler (usually a type of carbon black or silica) are selected depending on the intended application of the tyre being manufactured, which may include requirements such as superior traction in wet conditions, optimal performance or long-wearing, heavy-duty agricultural use.
A number of other materials such as antioxidants, curatives and accelerators are also used in the process, helping to “cure” the tyre and ensure its elasticity.
FABRIC & STEEL
The next integral “ingredients” in the manufacturing process are Fabric and Steel cords used to reinforce and strengthen the tyre compound. Fabric cord (based on strength, stretch, shrinkage and elasticity) is treated with adhesive to ensure bonding with the rubber. Steel cord is coated in brass and twisted into strands, with quality evaluated in terms of things such as strength and stiffness. Both of these types of cord are kept in temperature and humidity-controlled rooms at the factory prior to being added to the compound.
THE BELT & PLY
A process called “calendaring”, which involves the Belt and Ply comes next!
A heavy-duty calendar machine with steel rollers presses the fabric or steel cords onto and into the rubber during a number of steps, firstly combining the rubber compound and cords (at controlled tensions) to create a continuous sheet of rubber and cord composite. Once in sheet form, the rubber sheets are passed through more rollers to optimise bonding of the different elements and later cut into different sizes, shapes and angles depending on the required contour of the tyres being created.
The manufacture of the Bead is the next component, which has the role of securing the tyre to the vehicle’s rim.
The bead is made up of a number of elements including steel wire loop covered in rubber and wound around a few continuous loops, the bead filler (made up of a very hard rubber compound), the “chafer “(with the role of protecting the wire bead components), the “chipper” (which protects the lower sidewall) and the flipper (which holds the bead in place). It is vital that the bead is not too loose (or it could come off under loading and cornering), so the precision of the bead circumference is an important part of the bead manufacturing process.
The tyre’s Tread (arguably the most visual part of the tyre and the one that understandably gets the most attention) is the area of the tyre that connects the vehicle with the road.
The tread is made up of three areas: the tread, tread shoulder and tread base. During the manufacturing process, rubber compounds are extruded through a specialised die plate tool, which is used to create the shape and dimensions of the tread before it goes through an extensive cooling line to cool and stabilise it before being cut to the specified requirements of the tyre being built.
The Sidewall of the tyre is created using a similar method to the tread – although its structure and the compound are very different. The process can often also be more complicated, depending on sidewall designs and whether white sidewalls or lettering are required.
THE INNER LINER
Finally, there is the Inner Liner which keeps the compressed air within the tyre and maintains tyre pressure. A type of rubber called butyl rubber (or halogenated butyl rubber) is used for this specialised purpose, again using the calendar machine.
PUTTING IT ALL TOGETHER – BUILDING THE TYRE
Once all these tyre components have been manufactured, they are assembled and the end-product tyre is built on a flat drum using a very high-tech robotised machine, in a two-stage process.
The first stage involves wrapping the inner liner around a drum and then building the body of the tyre, positioning the bead and inflating a bladder on the drum to force the body of the tyre to cover the bead. The sidewall is then pressed on. In the second stage, the belts, nylon cap and tread are applied – before the tyre goes to be cured and the tread pattern introduced.
Once the build process has been completed, the tyre then goes into Curing. Tyres are cured in batches using chemical processes at high temperatures and at very high pressures. The uncured tyre is placed into a mould at a certain temperature and the tyre compound then flows into the mould, creating the tyre details and sidewall design. It is essential that the mould is not opened until the curing reaction has taken place and the rubber is vulcanised giving it the required strength, resilience and elasticity to perform as required.
In the final stage of the manufacturing process, the tyre is carefully inspected by an expert to check it meets up to safety and performance standards. This is done visually and by x-ray (to ensure nothing is missed inside or out)! The finished product is also inspected for balance, weight, uniformity and durability – and if it successfully passes the examination, the tyre is ready to hit the road.