Winter Tyres are Essential for Cold Weather Driving
Winter tyres provide unbeatable grip in the cold and wet ... but most Australians have never even heard of them
At seven degrees Celsius, in the wet, the tyres on your car start going out to lunch. At zero degrees and below, they stay for dinner and a six-pack, leaving you skating on thin ice, literally. Swan Lake at 70 km/h on black ice is never a performance worthy of rave reviews; it often ends in tears, and it’s always cause for concern (or at least in the back of your mind) during ski trips, or touring Tassie’s magnificent Targa roads in winter.
Some very clever tyres, however, are designed specifically for enhanced cold-weather grip.
To prove this point, and to issue a brace of pats on the back all round as well as a rev-up for the launch of the P-Zero Corsa (a road-registerable grooved slick in sizes up to 285/35R19 with more outright grip than P-Zero Nero), Pirelli Australia quietly took a bunch of its top retailers (and one journo) to Snow Farm in New Zealand last winter.
Snow Farm, up in the alps -- elevation: 1600 metres, call it 5000ft -- is just outside the winter ski Mecca that is Queenstown. It experiences just two seasons: last winter and next winter, often contemporaneously. This is why it excels at two things. It facilitates world-class cross-country skiing, and cold-climate automotive testing. The former is open to anyone, while the latter is shrouded in high security and marketed only to those in the know. But it’s a safe bet that many an unwitting Kiwi cross-country skier has come face-to-grille with the automotive development scoop story of all time ... without realising it.
Snow Farm is practically the only place on Earth with a viable winter automotive proving ground available -- and here’s the kicker -- when every northern hemisphere winter test site is shut down and out of play during the northern summer.
Snow Farm’s seasonally out-of-phase relationship with its on-paper northern competitors is what allows it to overcome the tyranny of distance. Moving tonnes of men and material halfway across the world and back is a small price to pay for slashing your winter product development lead time by a massive six months. Well, maybe not a small price, but an economically rational one, which explains why the facility’s 14 different sub-zero handling tracks are booked solid a year in advance. Most European car makers, including Mercedes-Benz and Porsche, as well as many Japanese and American manufacturers, plus product suppliers -- mainly tyre companies and component conglomerates like TRW -- derive benefit from ‘off-season’ winter testing here.
A handful of key members of the 180-strong Pirelli international tyre development team are shipped here annually, for a little more than a week. Last year marked the 10th anniversary of Pirelli’s pilgrimage to the NZ proving ground. They came with 70 sets of prototype tyres and all the requisite hi-tech tyre-testing accoutrements (total mass: seven tonnes of it) hell bent on carrying out 8000 separate braking and traction tests, plus a couple of far less rigorous or repetitive PR exercises...
...which is why we are all standing shivering outside, on what the top of a mountain looks like after it has been energetically renovated using a D9 ‘dozer and a spirit level, for several football fields in every direction. The temperature? Minus six degrees C according to the trackside digital ambient-air thermometer. There is a slalom-on-snow competition under way. A VW Golf on summer tyres races its identical twin (albeit wearing an Audi A3 badge) on winter tyres. Result? The Audi hoses the VW every time, irrespective of driver. Winter tyres work.
If you’ve lived in Europe, Canada or the top half of North America it probably comes as no surprise that tyres can be had in both ‘summer’ and ‘winter’ flavours. In fact it’s commonplace to own two sets (one of each, mounted on rims) and alternate them each year in autumn and spring. In parts of Europe, the use of winter tyres in the colder months is mandated. Upmarket car dealerships even store customers’ out-of-season sets as a relationship-building exercise, and also as a ploy to get customers into the showroom at least twice every year.
However, if you’ve lived parochially between the 40th parallels of latitude for the duration of your life, the existence of winter tyres comes as rather a surprise. Because Australia is a wide, brown land and not a narrow, white one, the overwhelming majority of tyres available here are summer tyres.
Pirelli’s global tyre testing manager, Stefan Kuster, explains the dominance of winter tyres in cold climes: “At zero degrees C in the wet, our Snowsport V cuts 10 per cent off the stopping distance from 80 km/h, compared with an equivalent summer tyre. In the snow at that temperature, in a stop from 50 km/h the difference is 20 per cent -- more than eight metres.”
Kuster says chemistry has more to do with a winter tyre’s performance edge in cold, wet conditions than any other single factor. “During the past 10 years, advances in compound technology, in particular the development of advanced polymers and silica, has boosted both cold-weather and wet weather grip,” he says. “Basically, the compound in a winter tyre stays soft at lower temperatures. The summer compounds would be too hard to provide effective grip at those temperatures.” The reverse is also true: winter tyres start losing their edge at around seven degrees C, where the performance of summer and winter tyres overlaps. From there, winter tyres slot in ever further behind the eight ball the balmier it gets.
Visual cues separating snow tyres from summer tyres are minimal, but many winter tyres that comply with a joint US/Canada snow performance standard are marked with a distinctive snowflake-on-mountain range graphic embossed on the sidewall. About the only giveaway, tread-wise, are the winter tyres’ profusion of sipes (the little water-dispersing ‘cuts’ found in the tread blocks of most tyres) which greatly outnumber those on summer tyres. When the tread deforms under the influence of braking, acceleration or cornering, these deflect to offer their sharp corners or edges, which helps them bite into ice or packed snow. Stabilisers to improve overall tread rigidity are built in at regular intervals deeper inside the carcase.
Pirelli says the Australian market for winter tyres is microscopic, but could expand to as much as ‘tiny’ with increased product awareness. It currently imports winter tyres in response to specific customer requests, usually for ski-field duty. Across the Tasman, NZ police are evaluating the use of winter tyres in colder regions.