I have a set of Pirelli Scorpion STR tyres on a Volvo XC70. I discussed winter tyres with my local tyre dealer last year and he pointed out that Scorpions are designated M+S and, although not true winter tyres, are designed as all-weather tyres. My experience with these tyres during the last two winter in snow and ice was that they performed extremely well even in deep snow. I have no experience of winter tyres and would value your opinion about this issue. I always carry chains for the front wheels in case of exceptional weather conditions, particularly in the Alps.