So what's the difference between summer and winter tyres? It's just rubber isn't it???
Cold Weather tyres not only improve safety, they also shorten braking distances and increase performance. Remember, Summer tyres are not designed to be used in cold weather. At cool temperatures, Summer tyres are less effective on all types of road surfaces. Cold Weather tyres are made of a special rubber compound suited to these low temperatures and unlike Summer tyres, they do not harden in the cold, which increases their performance and grip.
My experience...
So I have two sets. One set of rays alloys with Michelin pilot super sports (mpss) and one set of touring alloys with Michelin pilot alpin pa3 tyres.
The winters have done About 6000 miles. Fronts are down to 7mm from 8mm. Rears still at 8mm.
So I should get a few years use out of them. I guessing four years for the fronts.
I bought mpss for the fronts in may 2012 and they are currently on the legal limit after having done about 13500 miles.
The winters definitely provide more grip during the colder weather and I had no trouble in the snow. Yes you can also be fine with summer tyres if you drive carefully but winters are definitely safer.
One bit of info I found was that apparently if braking on snow from 50kmph to a halt, it'll take 48m on average summer tyres with an average car. Its 24m with cold weather tyres.