Tractor tyres are rarely thought about unless they are being purchased or things go wrong, and then they become the immediate centre of attention for an hour or two, until the next time.

Yet in between these intermittent periods of focus, they remain what makes expensive farm equipment useful and efficient so they deserve a little more consideration than they are used to.

Unfortunately, tyres suffer something of an image problem; they are ubiquitous and are an unattractive colour, yet they are the product of a good deal of thought, chemistry, and engineering.

Nokian tyres on Fendt — Nokian makes tractor tyres to suit farms, forests, and the road

Nokian Tyres of Finland is one company that takes tyre manufacture and utility seriously and – in a world where the retail price is such a huge factor – it finds itself caught between producing a quality product or swimming with the rest of the trade in a murky sea of discounts.

This is a difficult balancing act but, as a smaller player in the grand scheme of global tyre production, Nokian Tyres does tend to focus on areas where the big companies are simply not interested because of the lack of volume, or where the value of a good tyre is appreciated by the end user.

Early days

Finland does not immediately come to mind as a hothouse of the rubber industry yet the roots of Nokian Tyres go back to 1898, with the first tyres being produced in the early 1930s and the company taking on its present name and form in 1988.

Today, its main line of business remains light truck and passenger vehicle tyres, yet it also has a heavy duty division which caters for trucks, harbour cranes, mining equipment, and of course tractors and trailers with much else besides.

While price cannot be ignored, quality – especially when measured in terms of robustness and longevity – is the major objective when designing and producing the whole of the company’s range.

The basic principle of a tyre is universal however, and that is to trap air between the the wheel and the ground to produce a cushioning effect and enhance the grip so that power produced by the engine can be more efficiently turned into tractive effort.

When that power is measured in hundreds of horsepower and the surface may be not be either cohesive nor smooth, then the demands upon the tyre multiply greatly and its structure has to be carefully designed to enable it to cope reliably.

Tyre development

Nokian Tyres products are manufactured in a highly automated factory where tyre build is a skill that is complemented by machinery of the company’s own design and is therefore unique to its production process.

Bringing a new tyre to market can be a fairly quick process – simply copy another company’s product, which unfortunately is not unknown in the tyre trade, and Nokian Tyres has suffered from pirating in the past.

Rubber lab — A rubber laboratory was set up in Helsinki in the 1920s to help develop the industry in Finland

However, there is a more honest way, and that is to spend the time and money in designing and testing a tyre from scratch, which is how the company goes about product development.

The first questions designers should ask is in just what environment is the tyre to be used and what loads is it expected to experience? This will influence both the structure of the carcass and chemistry of the rubber compounds.

Product architecture

The structure is mainly a matter of choosing and placing the chords, steel bead, and rubber thickness to create a desirable profile, while the chemistry is a closely guarded secret and not divulged outside of a small group within the company.

Yet all tyres have three basic components in their compounds, natural rubber, synthetic rubber, and a filler, plus a complex mix of additives and enhancers which is where Nokian Tyres scores against its competitors.

Cross section cut from a tyre. Note how the sidewalls flare out as the bead no longer pulls them towards the centre

One of the trends within the industry over the last couple of decades is to use silica as a filler rather than carbon black.

This has resulted in very positive improvements in tyre characteristics across all sectors of the market.

There may be up to five different rubber compounds used within the same tyre, with the inside layer always being a softer mix to provide an airtight seal while all chords and beads are first coated with a latex-based solution to ensure they are kept separate within the carcass, reducing the risk of overheating.

Tyres awaiting testing — Tyres at the R&D centre, which often tests them to the point of destruction to find where they fail

It is a complex business and a tractor tyre will take around five years to develop and test in both the factory and field, before being released onto the market.

That testing will include at least three years of farm trials and up to 15 samples being tested to destruction in the R&D centre, which, when added to the cost of the moulds, all adds up to hefty investment in product development.

Nokian factory

Once the design is finalised, it moves into the production stage at the factory which, despite being a rather grand and noble brick building on the outside, is highly automated and modern within.

Images of the manufacturing area are quite deliberately rare and certainly not encouraged. Suffice to say that much of the automation utilises machines that the company has designed itself to ensure that the tyres are built as intended.

Nokian Tyres factory — The factory at Nokia now produces only heavy tyres. Production of car tyres takes place in Romania and Tennessee

At its heart lies the mixing and preparation of the compounds, which are then rolled into sheets for cutting into bands to suit ether radial or cross ply construction.

The tyres are then made up in layers, with the addition of the beads to form what is known as a green tyre.

This looks nothing like the finished product, being a long flabby bladder-like item that is transformed into a tyre in a heated mould which not only gives it the final shape but, at around 170°C, also transforms the rubber through vulcanisation.

This part of the process can take up to eight hours for ultra heavy-duty harbour crane tyres but is usually much less for tractor/trailer tyres.

Once moulded, tyres are given a serial number before being taken for final inspection before dispatch worldwide, including Ireland, where the company has long had a presence but one it wishes to grow.

Early days

Tyre development

Product architecture

Nokian factory

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