Hi

my personal reasoning:

4WD splits traction on the wheels when some of them loose grip, then when one loose grip, the traction goes on the other three, when two loose grip traction goes to the other two, when three loose grip the traction goes to the remaining one, when four loose grip ... :-/ ... you are anyway screwed ;-)

SNOW TYRES improve the grip of all the wheels on a slippery surface, like water, mud or, as from their name, snow (not ice !), then they increase the likelyhood of having one or some wheels with grip.

Then I'd say the snow tyres are anyway beneficial on a 4WD car.

Ciaociao

Fabrizio

PS: I heard also about "legal/insurance" issues, but I don't know if they are just urban legendes

Oh, I forgot to say:

4WD is about TRACTION, then it helps you to keep the car moving and accelerating, but what about stopping or driving in corners ?

Would 4WD be of any help when trying to brake and stop the car on a snowy road ?

Would 4WD help you in any way when driving in a corner and having the car slipping to the outside ?

What would you need there ?

... more traction ? ... or more GRIP ?

What is giving you grip, regardless you are accelerating, braking, going straight or in a corner ?

Yes ! Tyres !

Ciaociao

Fabrizio

hello all,

snow tires are imposed by law as of temperatures below of 7°C, with a strict minimum of 4 mm profile depth whether it be a “normal” car or a SUV.
as of this moment, the rubber - particularly on summer tires - turns hard and hence has less grip, think breaking on a heavier SUV going downhill…

wintertires offer an extralayer of rubber and remain more adhesive in cold and humid conditions.

you may not only get a hefty fine by the police, but you also dramatically increase the emergency breaking distance, if you do not change to the wintertires…

be safe!

Patric

Snow tyres are not imposed by law in CH. It's obvious to put winter tyres on your car, no matters if it's 2 or 4 wheels drive, but nothing to do with law... ;-)

Finnish guy here, I know something about the topic :-)

Yes. You do need winter tyres on a 4WD. As someone said above, it's not only the traction. It's braking and turning you need to worry about.

Ordinary tyres are useless on snow. Snow fills the texture which is designed to channel water rather than snow. Ordinary tyres perform as good as slick racing tyres on snow, that is: not very well.

Swiss insurance companies require using winter tyres. Most alpine roads require either winter tyres or snow chains when it's snowing (the blue sign with a chained tyre on it). 

When choosing winter tyres, I'd recommend sticking with the 'premium' brands: Michelin Alpin, Bridgestone Blizzak, Dunlop Wintersport, Contintental, Goodyear and Nokian (of course). 

Compared to summer tyres, an ideal winter tyre is more narrow, thicker and of slower speed rating. For instance, if the summer tyre is 245/40/18V, the winter tyre could be 205/55/17H.

If you drive to the alps, keep a pair of snow chains in the boot. Even when your car is equipped with winter tyres. 

If you drive on mostly flat terrain, where there is rarely any snow/ice, you can get around with ALL SEASON TIRES. They're not great at anything, but are OK in every situation...

Firstly my thanks to all who posted a reply to my query. I have been doing some more research (which is probably what I should have done in the first place!!!) and have found that by law - in Switzerland at least-it is not a requirement to fit snow tyres. In saying that it seems to me that common sense DEMANDS that you do. I was bought up in the south of NZ where icy and snow bound roads were reasonably common and drove on those on ordinary tyres (I don't think I ever heard of snow tyres before first living in Switzerland some 6 years ago !!) with no problems but then we always drove to the conditions that prevailed - something that I don't always see here. Once again thanks to all for your comments and now I will go and see what a set of tyres is going to set me back !!! Cheers Jeff

I'm waiting to see if my magical winter tires suddenly start gripping when the temps drop below 7C.  I almost killed an over-enthusiastic, tail-wagging Bernese last night because my poxy winter tires wouldn't stop the damn car.  This is my third winter here with the car and the first with winter tires (I left it parked when road conditions were poor).  My "summer" tires had slightly less grip than normal at 0C temps but these winter tires are f%&king lethal at 11C.  Meh....

I had winter tyres on my all wheel drive last winter when the snow hit in Geneva  for the first time.

The snow driving was fine, and in fact I've driven the same car out of a 1.2m overnight snow drift in the mountains with no problems.

It was ovbious who had winter tyres and who didnt... Im guessing sideways driving around roundabouts was fun for some ;-))

However .... the moment the packed snow had a layer of ice on it one night my winter tyres were as helpful as a chocolate teapot.... I had a prang... no fault on either side... the only thing that "might" have worked for either car  would have been snow chains or studded tyres.... In Geneva ? mmmmm....

Anyway. lesson learned... if you break on ice...you speed up... and turning the steering wheel frantically in any direction, does absolutely Feç all

Why does Geneva have so many accidents on the snow and ice?

Well we have 1000's of internationals here who rotate every year, many of which come from countries that never have snow or ice... they still drive to work... mostly in a state of absolute panic Im guessing... but...anyway.... oh, and you also have the Frenchies who still drive too fast for the conditions... :-)))

Im guessing were due a huge snow dump this year... and there are many reports that there are not enough tyres to go round... so get em early..

May I add 2 or 3 things ?

Likka mentionned a very good nordic brand : Nokian. They are a bit cheaper than other big names but they are absolutely awesome. During the previous 3 winters, my car was equiped by Nokian WRG2 and they're just amazing (I live in pre-alps). Period.

If you loose control of your car, you will receive a bill + a driving licence withdrwal, no matters the tyres. If you loose control in August, with regular tyres, sanction will be the same ;-)

With modern tyres, size doesn't count. Technology and rubber are totaly different now than 5 or 10 years ago. My car is on 245/18 both in summer and winter. Ok, I have a 4wd drive but believe me, no problem to clim walls :-)

In some weather conditions in Geneva...like 16th Dec last year... even Snow ploughs had trouble... theres no guarantee to anything...

Put it this way, 4 wheel drive isn't gonna help you when you're sliding downhill. Is it.

Just a bit about my experience

I used to drive a E Class çmatic without winter tyres under the snow. I could drive in a very safe way (acceleration, curves, breaking is VERY much better) and decided to install Vresdestein Wintrac ... Night and day. When you drive at 20km/h with summer tyres, it's 60km/h with winter ones

On my current 4X4, I've just installed Pirelli Scorpio Snow which seem good

TAKE CARE : already some out of stock according to dimension (ie 255/50 19" runflat)

Please read I COULD NOT drive.....