For snow and/or temperatures below 5°C, the Nokian N-rated version for the 997 Turbo is probably the best choice.
If you don't have much snow but cold winters anyway, do not go with the Nokian. The Nokian is not so good on dry pavement, especially when temperatures rise above 5°C.
At temperatures above 5°C, the Nokian doesn't feel to precise, it feels somehow "soft" and it seems to lack sidegrip.
For snowy regions and temperatures below 0°C, the Nokian is definetely the best choice.
Funny thing: Porsche didn't offer a good winter tire for our Cayenne Turbo S almost two years ago. The Pirelli Scorpion sucked bigtime, it was the only approved tire in 19'' at that time.
So I exchanged the Pirelli with a non-N rated Nokian according to the advice of a Porsche engineer who apparently has tested this tire in Weissach.
Wow, what a difference on snow, especially braking was much improved. Unfortunately I learned very fast why Porsche didn't choose this tire for the Cayenne, it wasn't just precise enough on dry pavement, the same "soft" feel and missing sidegrip on dry and somehow warm pavement. The 2nd generation of the Cayenne has a much better choice of winter tires, for almost all purposes.
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RC (Germany) - Rennteam Editor 997 Turbo, Cayenne Turbo S, BMW M3 Cab DKG, Mini Cooper S JCW