In contrast to last month’s Rallye Monte-Carlo where drivers had four options, regulations limit each supplier to one type of studded tyre for this once-a-year snowfest in the Scandinavian forests.
Both suppliers’ offerings have 384 metal spikes, each 20mm long, inserted into the tread block on each tyre. The studs can protrude from the rubber to a maximum of 7mm and provide astonishing grip as they cut into the frozen ground beneath the snow and ice.
Michelin, which supplies the majority of the WRC drivers, will provide an evolution of the X-Ice North tyre used in 2011 and 2012. After two WRC tests in December 2012 and January 2013 the firm says the new rubber, the X-Ice North 2, is a big improvement in performance terms.
Changes are focused chiefly on a revised tread pattern and the amount that the studs protrude from the rubber blocks.
Michelin Competition's technical director Nicolas Goubert explained the factors that his engineers had to consider when designing the new tread pattern: "A particularly open pattern will allow snow to be cleared quickly but, on the other hand, a compound that is too flexible can have a negative effect on the car’s stability. An excessively open tread can also result in the rubber blocks being too fragile for exposed dirt and stones.
"The development team spent several months optimising the overall package and the result is a new tread pattern which features some innovative technical solutions with regard to its so-called ‘sea-to-land’ ratio and the rigidity of its blocks."
The amount of stud sticking out from the tyre is another tricky compromise. "The longer the exposed part of the stud, the more grip it provides on ice. However, excessively protruding studs run the risk of being pulled off because each time they strike the ground, the weight of the car causes them to buckle flat," explained Goubert.
"When exposed to long portions of dirt, very long studs, or studs which are made from too soft a metal, are prone to being pulled away from the tyre or becoming damaged. When designing the X-Ice North 2, we worked on the proportion of the stud that is exposed, as well as on our choice of metal with a view to improve the resistance of the spikes without compromising grip," he added.
DMACK’s new DMG-ICE tyre features a new construction and compound aimed at improving performance on frozen gravel and ice. And a revised ‘T-Bar’ studding method, which was developed in partnership with driver Jari Ketomaa and its motorsport partners in Finland, is designed to aid stud retention.
Dick Cormack, DMACK motorsport director, said: “Last year our weakness was on frozen gravel and we’re confident that all the hard work and technical development with our new tyre will really pay off. We’ve developed a unique studding method in-house and that gives us more control over the quality and studding process.
“However, the compound and construction has also been improved and we’ve seen real steps forward in terms of performance during winter testing,” he added.
Ketomaa won Rally Liepâja-Ventspils in Latvia last weekend, the second round of the FIA European Rally Championship, on snow and ice. He will pilot an Autotek-run Ford Fiesta RS in Sweden.
DMACK’s other top runners include Czech driver Martin Prokop in a Fiesta RS and MINI WRC driver Michal Kosciuszko from the Lotos WRC Team.