Nokian previews zLine summer range
A new Nokian Tyres summer range will be available in selected European markets as of spring 2013; named the zLine, the new line-up is aimed at the UHP segment and replaces the Nokian Z G2. The zLine will be available in 31 dimensions for 16 to 20-inch rim diameters and W and Y speed ratings.
In a statement released to coincide with the zLine’s official press launch, the Finnish manufacturer described the tyre as one that “excels under extreme conditions and is not afraid of changing road conditions or large changes in temperature.” Nokian also called it “pleasantly stable to drive in the varying Central European summer conditions.”
The new tyre’s handling and grip characteristics are said to have been “refined on the rough northern roads and the European high-speed circuits.” The zLine development team utilised high-speed camera footage when honing the tyre’s wet grip properties; Nokian says this provided essential information regarding the interaction between road and tyre. The tyre’s structure was evaluated through a combination of indoor testing and thousands of kilometres of test driving on different asphalt roads.
“The Nokian zLine is a professional in demanding driving conditions, thanks to its new generation of tread compound, nanotechnology layered structure, and tread pattern developed for fast driving,” states Juha Pirhonen, product development manager for Nokian Tyres. “It immediately responds to steering, which is an essential requirement for safe operation at extreme limits. In addition to the precise driving feel, these advances in technology also manifest themselves in the remarkable driving comfort of the tyre.”
‘Intelligent’ compound
To accommodate the up to 300km/h speeds potentially required of a Y rated tyre, Nokian developed a new compound for the zLine. It calls this ‘Nokian Intelligent UHP Silica’ tread compound, and says the rubber compound’s molecular chains combine with silica particles in order to form an extremely strong, yet flexible combination. Nokian also reports the new UHP tread compound was refined to have extremely low heat generation, and its ability to work across a wide temperature range is said to improve wet grip. “The feel of the road is perfect and provides no surprises under any conditions,” says Nokian in a press release. “The cut-resistant new compound also enhances driving comfort by damping the noise generated by rough asphalt.”
The interim layer underneath the zLine’s tread uses a nano-silica compound consisting of small molecules. Explaining its purpose, Nokian states: “This unique combination is remarkably quicker than standard rubber compounds in relaying steering movements. The gentle, reliable feel of the road is especially accentuated in cornering, lane changes and evasions. The lowest layer of the multi-layer structure is an exceptionally firm layer of rubber compound that reduces heat generation and lowers rolling resistance.”
Asymmetrical inside-outside tread
The tread pattern found on the Nokian zLine is similar to that on other Nokian summer tyres designed for fast driving; the tread is an asymmetrical inside-outside pattern. The rigid inside and outside shoulder area connects with block patterns that are bound together by longitudinal ribs. The wide ribs are designed to stiffen the tyre and reduce the movement of the pattern blocks during road contact. The tread model is very rigid, which Nokian says translates into good control and handling at higher speeds.
The longitudinal ribs next to the inner shoulder are dominated by deep lateral grooves designed to stabilise handling. At the same time, Nokian’s ‘Hydro Grooves’ are meant to prevent aquaplaning by storing water from between the surface and the tyre, and by guiding the water into the longitudinal grooves. To combat aquaplaning, separate ‘Swoop Grooves’ were also shaped in the transversal main grooves on the outer shoulder. These elliptical slots store more water as the volume of the transversal grooves increases. Nokian says the shape ensures that the zLine has excellent wet grip, even when worn.
The transversal grooves are cut to be more open, a design that, according to Nokian, accelerates the flow of exhaust water. The flow of the water displaced by the surface tread is also accelerated by the four wide and polished main grooves. The tyre maker boasts that, in addition to further improving aquaplaning properties, polishing the grooves gives the Nokian zLine “an even more appealing look.”
Driving comfort and durability
Semi-circular indentations on the walls of the transversal grooves, reminiscent of a golf ball, are there to provide additional driving comfort for the Nokian zLine. This ‘Silent Groove Design’ is said to reduce interior noise and external rolling noise. The indentations guide airflow, removing the noise waves caused by the edges of the transversal grooves and thereby preventing on unpleasant, howling sound found on some UHP tyres. The design also reduces air resistance and cools the surface of the tyre, in turn improving wear resistance.
As for product durability, Nokian states that even motorists who are used to higher speeds can rely on the Nokian zLine for years of service, even as the tyre gets older and wears down. The stiff steel belt pack, designed for fast Central European roads and combined with a double body structure, is made of high-strength steel wire; the tensile strength of a single wire corresponds to a mass of approximately 2,400 kilograms. A single tyre contains nearly 2.5 kilometres of steel wire.
As is the case on other Nokian products, the tread surface on the zLine is equipped with Nokian’s patented Driving Safety Indicator, or DSI. However, the Finnish manufacturer says that the DSI is now easier to use than ever before. The numbers indicating groove depth and the water droplet symbol indicating a risk of aquaplaning have been rotated to offer better visibility to drivers inspecting the tyres installed on a vehicle. The water droplet symbol disappears when tread wears down below 4mm, a level at which the risk of aquaplaning rises.
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