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Safety Technologies:
Square stud enhances grip on ice
TREAD NATURALLY WITH RAPE-SEED OIL
When Nokian Tyres made public the Nokian Hakkapeliitta 4
winter tyre, the first thing that drew attention was the numbering
of the series. Why Nokian Hakkapeliitta 4, when its predecessor
was Nokian Hakkapeliitta 2?
“The name comes partly from the new, square shape of
the stud. But perhaps even more significant is that we actually
jumped one generation in improving the tyre’s safety
qualities,” says Teppo Huovila, the R&D manager at
Nokian Tyre.
The square stud is the result of long-term development work.
The Nokian Hakkapeliitta 4 underwent wide-scale testing against
other tyres in different Scandinavian countries for two winters
and in ice arenas during the summertime. Developing a new
tyre family takes from two to four years.
“We started calling into question the shape of the studs.
Traditionally they’ve been round or oval, but we tried
many different geometric shapes and computed their effectiveness.
The aim was to develop a safer tyre,” Huovila says.
In the end the square stud proved to be the best. The hard
metal pin and lower collar are square. The grip was improved
by orienting the stud to an angle so that its edge hits the
ice first.
Square studs have been tried before, but the development
of material technologies has made it possible to produce their
main components better. The hard-metal stud bolt is made using
powder metallurgy.
Grip improves by a tenth
Huovila says the square stud and the other new characteristics
of the Nokian Hakkapeliitta improve the grip by four to ten
per cent, depending on the conditions. “An improvement
of ten per cent is a considerable achievement,” Huovila
claims.
In addition to the square studs, the grip was enhanced by
widening the tyre’s tread. This enabled the studs to
be placed as widely as possible in 14 rows. The wide, straight
tread keeps the tyre stable even on a dry road.
Environmental considerations are a feature of the Hakkapeliitta
4. Under each stud in the tyre there is an elastic cushion,
which absorbs the stud’s impact. This reduces wear on
the roads and the formation of grooves. “The grip isn’t
generated by the impact, so it can be softened. The system
also reduces the noise created by the tyres,” Huovila
says.
The elastic cushion also increases the stud’s durability,
and as the square stud stays fixed in the tyre better than
a round one, the tyres’ gripping qualities last longer.
The innovation is called the Nokian Eco Stud System 4 and
the patent has been applied for.
Improvement with rape-seed oil
Nokian Hakkapeliitta 4 tyres have been designed mainly for
the Scandinavian and Russian market. In the varying winter
conditions in these countries studs alone will not make a
winter tyre safe. The grip on the tyre’s tread has been
increased by using Finnish rape-seed oil. “Rape-seed
oil also improves the tyres’ tear strength considerably
in sudden braking and sharp cornering,” Huovila explains.
Other plant oils were tested besides rape-seed oil. One decisive
factor in the choice of the latter was the cost compared with
other natural oils. Besides rape-seed oil, only low aromatic
oils are used on a tyre’s tread and not high aromatic
toxic oils.
Nokian Tyres is the biggest tyre manufacturer in Scandinavia.
The company develops and manufactures summer and winter tyres
for cars, bicycles as well as tyres for various heavy-duty
machines. It has its own sales companies in Sweden, Norway,
Germany, Switzerland, Russia and the USA. The product development,
administration, marketing and most of the production take
place at Nokia. The company also has contract manufacturing
in Slovakia, Poland, the USA, Indonesia and Russia. The Group’s
turnover was 479.2 million euros in 2002 and the number of
employees at the end of the year was 2,585.
Photo: The new features that increase the grip on the
Nokian Hakkapeliitta 4 tyres are the four-corned stud and
the rape-seed oil added to the tread mixture.
Published 2002
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