THE TECH BIT
TYRES
We once tried driving a Porsche 911 Turbo on ice wearing its standard tyres. After a little practice we had the speedo needle beyond 200mph while the car itself wasn’t moving at all. Strap two bars of wet soap to the bottom of Usain Bolt’s feet and he’s not going to win the race to the far end of the tiled changing room, is he? To move you need friction.
On ice, this means cold-weather tyres, although we usually refer to these – incorrectly – as winter tyres. Yes, they are designed to cope with snow, but frst and foremost they’re designed to work when the average daily temperature drops below 7°C. That’s because the key diference is the one you can’t see – the compound. Cold-weather tyres have softer compounds, typically using a higher percentage of natural rubber instead of silica. This allows the tyre to mould itself to tiny imperfections on the road surface, increasing the contact patch and therefore the grip.
Beyond that, there’s the tread, particularly the little cuts in the tyre. These are called sipes (invented by a man called John Sipe in 1923 who cut grooves into the bottom of his rubber boots to stop him slipping on the foor of the abattoir where he worked…), and as you drive along, these fex, allowing an edge to bite into the surface. Wider channels in the tyres are often designed to retain loose snow, as snow binds well with other snow…
Beyond that, most Scandanavian countries advise the use of studded tyres – as ftted to the Tesla and 911 GT3. Studs are put into the surface of the tyre and normally consist of an aluminium or steel footing and then a super-tough, abrasion-resistant tungsten-carbide head that projects about 1.5mm above the surface. Around 60–120 studs, each weighing 2g, are usually ftted per tyre. Both the Nomad and RX2 ice racer were ftted with competition spikes – WRC regulations allow roughly 400 of these per tyre. They look like something out of Death Race 2000, but if you’re serious about grip…