Nokian addresses weather vagaries with WR D4
Winter means different things to different people depending on where they live, and thankfully tyre makers are acknowledging this. Both Pirelli and Michelin recently added summer/winter tyres for temperate European climates to their portfolios, and winter tyre pioneer Nokian Tyres has now introduced a product it describes as a “versatile chameleon for winter roads” – a tyre that not only performs well in snow and slush (real winter weather, to use Nokian’s own words), but also in the wet weather that many of us more commonly encounter in the colder months. The Nokian WR D4 is scheduled for release in autumn 2015 and is promoted as the “world’s first premium winter tyre for passenger cars” to achieve an ‘A’ European tyre label rating for wet grip.
“Nowadays, winter weather in Central Europe tends to vary between blizzards, driving rain and dry periods,” comments Nokian Tyres upon announcing the new tyre. “The Nokian WR D4 is created for varying weather, and it represents the finest in Nokian Tyres’ tailoring expertise: it is an eco-friendly quality tyre that masters the changing conditions. This uncompromising winter tyre represents the new generation that follows the Nokian WR D3, the winner of multiple comparison tests in motoring magazines.”
A roll call of proprietary innovations
Tyres & Accessories hasn’t actually encountered the Nokian WR D4 yet, and the product press release is crammed with news of impressive-sounding propriety innovations whose names are meaningless to the uninitiated. The tyre’s tread, for example, glories in Nokian Block Optimized Siping (Each tread block and sipe has a specific role, says Olli Seppälä, product development manager at Nokian Tyres), Snow Performance Blocks (Seppälä describes these as small, heavily siped tread blocks that are split into groups of three and improve grip on snow), a Steering Precision Rib (a large rib in the tread’s centre), Stiff Handling Blocks (with heavy sipes to improve traction; these become shallower when moving away from the centre of the tread and towards the shoulder), Slush Blower technology (slanted grading on the back edges of tread blocks that shoot water and slush out of the grooves) and a Deep Snow Booster (which said to ensure grip during heavy cornering and while driving in deep snow).
This richly-featured and “high-technology functional” tread pattern is one of two factors Seppälä credits the WR D4’s grip and handling properties to; the other is the compound used in the tyre. This has been named the Nokian Twin Trac Silica compound and is said to be a combination of the Northern European winter compound used in Nokian Hakkapeliitta and a silica-based compound intended to deliver performance in milder weather. The compound contains natural rubber, silica and canola oil; Nokian Tyres says its “unique particle distribution” ensures peak performance for snow and wet grip.
“This state-of-the-art compound innovation also improves driving stability and wear resistance,” the tyre maker elaborates. “The large amounts of natural rubber and canola oil in the entirely new rubber compound ensure that the excellent winter grip properties remain the same even as temperatures change and the kilometres add up. The canola oil added to the compound allows the silica and natural rubber to work together, improving the ice grip and tear strength of the tread compound. Tear strength makes the tyre extremely resistant to wear, impacts and punctures.”
Nokian Tyres says testing indicates the “lateral and longitudinal ice grip of the Nokian WR D4 is supreme” while the tread pattern and use of silica gives the tyre “extremely low rolling resistance.” Driving comfort is reportedly increased by the use of another snappy-sounding innovation, Nokian Silent Sidewall Technology. This rubber compound between the sidewall and tread is said to actively filter the sound and vibration originating from the road surface, thus preventing the passage of sound waves through the sidewall into the rim and further into the passenger compartment.
As already mentioned, several the WR D4 sizes have been given an ‘A’ label rating for wet grip. The entire range covers fitments for 14 to 20-inch rim diameters and speed ratings from Q (160 km/h) to W (270 km/h), and includes run-flats and fitments for electric vehicles.