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Winter tires

Central Europe in the background as Nokian Tyres launches the Winter WR D4. Tested in Lapland, the new tire shows perfect balance of performance on both snow-covered and dry roads.


Sabrina Negro


“Hakkaa päälle!”. At the war cry (“cut them down!”) of the Hakkapeliitta – Finnish knights that served the King of Sweden during the Thirty years war - we joined the toast proposed by Antti-Jussi Tähtinen, Nokian Tyres vice-president of Marketing and Communications, at the end of an intense day of test track activities.  Under testing was the new Nokian WR D4, the latest winter tires produced by the Finnish manufacturer, that 80 years ago invented the first winter tires, and fittingly called Hakkapeliitta.



“White Hell”?

Outside, the Arctic beauty of the Finnish Lapland, with its snowy fir forests gently turning into picturesque wide open spaces. Here, a few hundred kilometers north of the Arctic Circle, in 1986 NokianTyres built the Ivalo Testing Center, 700 hectares where the research and development team, as well as test drivers, put tires to the test in extreme driving conditions.


Marking the entrance to the northernmost test center in the world is an imposing gate studded with sharp icicles and the menacing words "White Hell”. More than 20 different testing circuits on snow and ice that extend for more than 100 km, an indoor ice tunnel in which it is possible to maintain constant conditions during tests on ice. Here temperatures can vary up to 40° C in one day: true “infernal” conditions for the more than 20,000 tires tested here every winter, but to us – that for a day we had access to it - it seemed like the best amusement park.


Take the frozen circuit for example: drifting at full speed, slalom between cones and braking tests. It's not every day you get to sit behind the wheel of an Audi RS4s equipped with Nokian Hakkapeliitta 8 supported by professional drivers! And since - especially in Italy - such extreme conditions are not frequently met, for the milder winters in Europe Nokian created the latest generation of winter tires, the WR D4.



Forget the weather forecast                                                 


The snowy North is its homeland, but the new WR D4 was specifically designed by the Finnish manufacturer for the ever-changing winter conditions of Central Europe, a market that in 2014 alone recorded the sale of 70 million winter tires.


We put the new WR D4 to the test at the wheel of Audi RS5s on snowy secondary roads and highways. The feeling of control and maximum grip was immediate even when braking at a brisk speed: credit goes to the functional profile and high technology combined to the Nokian Twin Trac Silica compound and Nokian Block Optimized Siping, says Matti Morri, Technical Customer Service Manager of NokianTyres.


Innovations that translate into concrete results: the directional profile is characterized by a central 3D support sipe system that ensures stability as well as quick steering response and two types of side blocks, which improve grip and handling on snow. More in detail, explains Matti Morri, the Snow Performance Blocks, in their special arrangement in groups of three, provide traction on snow, while Stiff Handling Blocks, on the edge of the tread, with pronounced grooves to increase traction, improve handling. Each of these elements of the tread features a large number of sipes of different size and shape that by "trapping" snow contribute to improve traction and stability while maintaining the stiffness of the tread by limiting tread deformation, and therefore consumption. The Nokian Twin Trac Silica compound combines two different compounds, one thought for the extreme Nokian Hakkapeliitta, and the other with a high silica content suitable for warmer climates. "Having added smaller silica molecules compared to previous compounds - said Matti Morri - has improved traction on snow and wet roads, while maintaining consistent winter qualities".



An A for grip on wet roads


And performance on wet roads is a source of pride for the Finnish manufacturer: the new WR D4, explains Morri, is the first winter tire to receive an A for wet grip in the European labeling system. Nokian well knows in fact that a product intended for Central Europe, with its long rainy winters, cannot compromise on wet grip. Too bad the polar conditions of Ivalo did not allow us to test the WR D4 in this respect. Performance on wet and dry roads of the new winter tire, Nokian guarantees, was perfected on several test circuits in central Europe. Thanks to this research, "SlushBlowers", developed by Nokian, have been inserted, grooves on the side edges of the tread blocks that facilitate the expulsion of water, slush and sleet actively counteracting aquaplaning and slushplaning, treacherous even for the most experienced drivers.


Going from snow-covered country roads to main roads and driving at full throttle, the contribution of the SilentSidewall technology, a thin band of a special soft compound situated between the shoulder tread and the sidewall, is noticeable, considerably reducing noise and vibrations that otherwise would move to the rim and the interior: the driving is smooth and fairly quiet, even at high speeds.


Available from autumn 2015, the range of sizes for the Nokian WR D4 is between 14" and 20", with speed codes from Q (160 km / h) to W (270 km / h). The extensive line-up offers customized dimensions for sports cars as well as electric vehicles, while some products employ special FlatRun technology. Moreover, many tires are marked with the abbreviation XL, to indicate the maximum load capacity possible for a passenger car tire.


Noteworthy is also the Driving Safety Indicator (DSI) patented by NokianTyres and placed in the center of the rib of the tire. The numbers on the tread - 8, 6 and 4 – correspond to the tread depth in mm. These indicators disappear, one by one, as the tire wears down. "Below 4 mm we can no longer talk about winter safety", said the Technical Customer Service Manager of Nokian who, upon learning that in Italy the legal limit is 1.6 mm (the same as on summer tires) shuddered, and not from cold, despite the Arctic temperatures.




Also Nokian produces its alternative to the seasonal tire substitution with an all season product. The NokianWeatherproof All-Weather is a winter tire that guarantees the driving stability and precise handling typical of Nokian summer products.

This tire, says Matti Morri, was also  tested in Lapland and, as far as summer performances are concerned, on race tracks in Spain and Germany at temperatures ranging from -10 ° C to + 35 ° C. Thanks to the high percentage of natural rubber present in the tire, it performs well in a wide range of climatic conditions, although, says Morri "at high temperatures the Weatherproof All-Weather will certainly have less stability and a lower mileage than a pure summer tire".

All sizes, for passenger transport, SUV and van, are certified for winter use by the 3PMSF symbol. The NokianWeatherproof will be available at retailers from April 2015.

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