A journey of the rubber that transforms into a tyre

A visit to the Apollo Tyres' manufacturing unit at Limda, near Baroda, made the DH correspondent realise that tyres are not just rubber mixed with a f

195/65R1591H. Wondering what this alpha-numeric code signifies?  No, it is not a Swiss bank code, for sure. It is a product code that we use in our day-to-day life. Unfortunately, we often fail to notice it.

It is the code of a tyre that one buys either off the shelf or comes factory-fitted with one’s vehicle. Here 195 stands for width of the tyre in mm, 65 for the aspect ratio, R for radial construction, 15 for the rim dimension in inches, 91 represents the load index, and H the grading that tells you the maximum speed your tyre would be able to withstand!

This particular tyre with an ‘H’ grading is suitable for speeds up to 210 kmph. If the grading were to be ‘Y’, then you can press the paddle of your vehicle to achieve the speed of 300 kmph without worrying about the tyre’s failure.

Imagine if you are using a wrong tyre and you are cruising along on the road at a speed of 70 kmph or 100 kmph, and the tyre gives way. At 120 km/h, a normal tyre is deformed — 30 times a second — and over a distance of 40,000 km, the tyre is deformed 60 million times!

A visit to the Apollo plant

To understand the science and art behind tyre manufacturing, it is best to meet the manufacturer directly. This correspondent did so by visiting the state-of-the-art facility of Apollo Tyres’ biggest tyre manufacturing unit at Limda, near Baroda, in Gujarat. Apollo is a home-grown tyre manufacturer established in 1972. Since then, it has been able to leave its footprint across 100 nations, with manufacturing facilities in India, Southern Africa, and the Netherlands. It is also India’s leading brand in the commercial vehicle segment, and third in the passenger vehicles segment with a 17 per cent market share.

Apollo’s main brands include Apollo and Vredestein, catering to passenger cars and commercial vehicles across different segments. While the Vredestein range are sold in the high-end luxury and performance vehicles, its other brands Regal and Kaizen (truck and bus tyres), Maloya (passenger vehicles), Dura (retreaded tyres) and Dura Tread (retreading materials) compete with the best in the markets.

Some of the leading vehicles that Apollo tyres come factory-fitted with are the Volkswagen Polo and Vento; the Skoda Rapid; the Hyundai i10 Grande; the Tata Bolt; and the Maruti Ciaz, among others. Apollo’s Limda plant builds tyres from passenger cars to those weighing over 3,500 kg, customised for mammoth mining vehicles. Spread across 5,25,000 square metres, the plant makes bias, radial, and off-roader tyres. It has a capacity to produce 18,000 of passenger cars (PC) and light truck tyres/day, 4,700 truck-bus bias tyres/day, and up to 10 large-sized off-road tyres every day.

Not just the rubber

The journey began primarily with getting the basics of tyre manufacturing. It is here that I realised that our tyres are much more than just rubber mixed with a few resins or chemicals. Today, modern tyres have only 85 per cent of rubber, with over 200 different inputs making up the remaining 15 per cent, including steel wires, brass mesh and several chemicals to make the tyre more stronger, long-lasting, and tensile.

The pre-manufacturing process involves planning and designing where the tyres are designed on computers to meet the mechanical and performance specifications of a particular vehicle. Multiple algorithms are run and mathematical calculations done to design a prototype tyre. The designed prototype tyre is then tested to function as per the desired characteristics on the computers before building a mould to prepare a physical product.

The key ingredient for any tyre is rubber and the entire process is all about how the rubber in its natural form gets transformed into a circular shape that the world calls — a tyre.

Four steps to get the perfect tyreTyre manufacturing is mainly divided into these steps:

Compounding and mixing
Material manufacturing
Making of a green tyre
Tyre moulding

Compounding and Mixing: The raw materials for tyre manufacturing includes imported and home-grown rubber, pigments, chemicals, fabrics and wires, among others. The process begins with the mixing of basic rubbers with process oils, carbon black, pigments, antioxidants, accelerators, and other additives, each of which contributes certain properties to the compound. It is carbon black that gives the tyres its colour, while chemicals like silica and sulphur provide different characteristics such as high friction (better grip) or high mileage (lower friction) for a passenger car tyre.

Once the mixing process is complete, the batch for a particular compound type is stored in the form of continuous rubber sheets, which is then sent to the next processes.

Material manufacturing: This includes various parallel processes like building the body of the tyre; the belt that helps reinforce the tyre body; the bead that holds the tyre against the rim; and the tread or zigzag lines on the tyre body that comes directly in contact with the road. The tyre body and belt are produced by coating steel cords with rubber. Strands of bronze-coated steel wires are mixed into rubber compound and prepared as sheets. These sheets are then cut to the required tyre size using an automated cutting tool.

Next, the rubber compound is heated, forced through a dye, and eventually cooled before tread or the sidewall is cut as per the required size. The tyre bead, which is made of steel, is also coated with rubber using similar process.

Making of a Green Tyre: Once the tread, inner-liner, sidewall, bead and belt are prepared, they are assembled on a giant roller drum known as a Tyre Building Machine (TBM) to form a raw tyre, known in technical parlance as a ‘Green Tyre’. Thus, the TBM is used to put all the components together and giving the Green Tyre its circular shape.

Tyre Moulding: The Green Tyre is then sent for the final step of making the tyre-moulding. Here, the Green Tyre is vulcanized for 8-10 minutes (length of time varies based on tyre size), to make it road-worthy. It also makes the tyre stiff and resilient. In the process, the operator primarily places Green Tyre inside the mould machine and the segments around the tread and sidewall are pushed inward, providing the tread its outer shape. Simultaneously, a large rubber bladder inflates the tyre. Depending on the type of tyre to be produced, the moulds are replaced. Apollo has over 160 different moulds to produce different tread-patterns. The manufacturer’s branding and markings — say 195/65R1591H — that tell you about the tyre’s characteristics, get engraved on the tyre sidewall during this process of moulding.

Once moulded, the tyre undergoes indoor as well as outdoor checks. The freshly prepared tyres are dispatched to be put on huge multi-level racks. It is as if you are in a tyre supermarket, wherein a large number of tyres are stored before they get dispatched to various locales across the globe. The outdoor testing, meanwhile, is primarily done to develop a market-ready tyre, and it can take months of testing, inspection and quality checks by a team of experts. So the next time you buy a tyre, just remember, you are not just buying a black colour utility product, but a product that involves both science and art to make your journey comfortable, safe, and one that would never pinch your purse.