Developing the safety properties of tyres from expert’s point of view

Safety tests of tyres can be roughly divided to two different subareas: structural tests and live tests. The structural tests of tyres are governed by certain authoritative requirements that must be complied with. Only after this, other properties can be customized. This means that there are various standards valid in Europe and other countries and continents that must be followed in order to get the approval to the tested tyres required by authorities. For example, the E approval used in Europe means that the tyre may be sold in countries which have entered into E marking contract without any need for additional testing.

Lots of standards to comply with

The E approval is used in all European countries, but totally different requirements cover, for example, the United States and China. The United States and China require the DOT marking and the CCC marking respectively. These different requirements and markings call for different types of tests.

Reconciliation of these various authoritative requirements is perhaps the most difficult part in our work. It would undoubtedly be good, if there was just one comprehensive standard that would be valid all over the world. Unfortunately, there is none, which is a nightmare for all tyre manufacturers.

These requirements, including the E approval, apply only to structural tests which do not test the properties of the tyres but only their structural strength. The structural test is always a so-called indoor test where the tyre is run against a drum with a specific load and pressure for a specific time period. The tyre must pass this test without any damages. The latest EU tyre marking label indicates the tyre rolling resistance (indoor test), adhesion performance on wet surfaces (outdoor test), and pass-by noise (outdoor test). In addition to other tests, these tests also increase workload in the R&D departments.

Different tyres for different conditions

Another safety testing method for tyres is the so-called live testing, where tyres are tested installed in a car. In live testing, the tyres can be customized so that they are suitable for different continents. For example, tyres that are designed to the Nordic market are somewhat different from those designed to other market areas. The purpose of the live testing is to find out how the tyres behave in different conditions. According to the tests, the tyres are then adjusted with patterns, tread mixtures, and structural details, so that they perform in the best possible way in the intended conditions. For example, the Hakka tyres were designed for Nordic conditions, and they are not sold in Central Europe at all. In Central Europe, our tyres are sold under Nokian brand and have been customized particularly for these conditions.

Our biggest competitors customize their tyres continent-specifically, and they have different tyres for the United States, Asia, and Europe. We always customize our tyres for the Nordic countries, Central Europe, and the rest of the world. For example in Central Europe, temperatures below +7 °C are considered as winter conditions, and here in Finland, summer temperatures may vary between 0 to +40 °C, which sets specific challenges to the development of tyres. Considering such broad temperature ranges as in Finland, we can confidently say that if the tyre performs well in Finland, it performs well anywhere. When comparing the Nordic countries to Central Europe in a larger sense, it must be noted that, e.g., road conditions and the composition of asphalt are totally different. This is why it is definitely sensible to customize the tread mixtures to the operating conditions.

Comments

  1. Peter says:

    Is the Hakka R that I can buy in the United States identical in “tread mixtures and structural details” to the Hakka R that is sold in the Nordic market?

  2. Tony Salter says:

    Hei Matti,
    I am an Advanced Driver by tests. I have experience but not necessarily good driving skills in all conditions. My friends, a couple of Suomis as well, suggested Nokian tyres for my Renault Espace ( shod in winter with Pirelli Scorpion STR (not impressed, especially on snow or ice affected roads). They also wear quicker than desired!
    My winter driving consists of numerous journeys from Eastbourne UK to Haute Savoie France via Belgium, Luxembourg and so on. Lots of rapid cold driving and then winter driving in the mountains.
    Your site and my friends both say use WRA3 tyres. My Renault Espace is now shod with them and ready for the winter test.
    I will let you know the result.
    My particular interest, – your advice is appreciated in your blogs- is why Nokian advise 0.2 bar increase over the car manufacturer’s advice on pressure. Standard pressure for my Renault is 2.5 bar (front) and 2.2 (rear). I do not see this advice from other manufacturers of tyres.
    What is the purpose of this increase as there is no written advice about what it achieves?
    Ystävällisin terveisin
    Tony Salter

    • Nokian Tyres' bloggers says:

      Hi Tony,
      As we use more block pattern type design + a bit softer compounding in M+S tyres, the tyre pressure should be a bit higher in order to get best possible handling on bare road.
      – Matti

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