Winter & Studded Tire Technical Discussion

[evolutionmovement]

Actually, I looked it up afterwards and found out I was wrong. They're legal from Nov01-Apr01. Don't believe what you hear!

[Canadian Turbo]

OK well I'm a Legacy central n00b, but here I can finally have some constructive input.

I always consider the source so.......
Firstly I live 1 hour north of Montreal. This area is notorious for deadly wet snow, ice literaly falling from the sky and 4 months of pretty much the worst road conditions possible.
I have had 5 subarus since I started driving 8 years ago and just about every winter I get new winter tires. I have done alot of research and alot of driving on ice and snow. My passion for AWD, Subaru and ultimately my SS is driving in the winter. This winter I have spent over 18 hours driving on a closed 3km ice course that winds very tightly and has streatches where I can hit 120km/h.

Tires I have had (or my GF or parents cars that I have driven enough to fell the tire);

Yokohama Ice ...something (poor)
TOYO G02 (good)
Bridgstone Blizzak 3 gerations of them (best non-studed)
Vredestein top of the line studed ice model (shit!!!!)
Nokkian Hakka 4 (best winter tire comercialy available)
Goodyear Ultragrip (poor-good)
Michelin Artic Alpin (worst winter tire ever, only good on pavement) the new X-ice is supposedly much better but michelin burnt the bridge with me when they made the alpin.
Marangoni Grip E+ (as good if not better grip than nokkian, only not so civilized)

First thing, if you really want to understand and not just be advised, then you need to know a little about the difference between static vs kenetic friction. If you don't, just google friction because I'm not sure I would be able to properly explain it here. I think my introduction to the topic was a children's book called "The Way Things Work"
So begins my rant

BEWARE of what you read. Reviews and tests of winter tires are often performed by people who live in parts of the US that receive little icy/snowy road conditions. Often, tires are given praise because they do well on pavement as well as ice and snow (Michelin ). Please be aware that pavement is your friend and ice and snow are not, and therefore I believe a winter tire should be a no compromise, all grip, ice and snow eating machine. In Canada 80% of all fatal winter car accidents are a result of ice or snow on the road, and NOT the result of winter tires that "aren't great" on pavement. I only read and sometimes trust european winter tire reviews.

Now to answer the original post, Yes on bare ice more surface area will give you better grip. All good winter tires have siping(squigly lines that run across each lug in the tread). This siping is designed to "squeegie" water out from under the tire so that the rubber can make contact with the ice. It's interesting to note that ice isn't even slippery, it's the very thin layer of water that is produced under the pressure and friction of the contacting surface (read tire, or ski, or boot when you fall on your ass) SO.... More surface area, more contact with the ice = more grip.

The very best tires for bare ice are Bridgstone Bizzaks period. Look at all that siping!! very very soft rubber, and lots of silicates in the compound. Note; the soft rubber is only in the outer 50% of the tread because it is not resistant enough to hold the rest of the tire together.

This type of tire will sustain the highest static friction forces, however the difference between the levels of static and kenetic frictions it produces are very great, so when it does slip and enter kenetic friction, slip will come on suddenly, strong and quite unpredictably.
Another caracteristic with non studded ice tires is that these tires offer lots of surface area to grip ice, but this in turn offers little room for snow to escape in the event you end up on snow, notice how close together the lugs are.
In short these are the best tires for anyone who will encounter winter conditions and snow, but never any real snow depth ie;when it's snowing hard I wait till the roads are cleared. Also someone who might not be able to cope with controled slipping, or maybe when you drive this car you don't expect to slip even in a controled manner. I put non studed tires on all cars except the one I use to have fun with (my Turbo SS )

On to studs..... Studded tires sacrifice soft rubber compound to be able to hold on to metal studs.
Studs are NOISY on pavement
Wear FAST on pavement
Not legal everywhere
Studded tires will almost always enter into kenetic friction earlier than a Blizzak because of the harder rubber and less siping (there are exceptions). However a studed tire closes the gap between the levels of K vs S friction produced and will therefore be much more predictable while sliping and maintain much higher levels of kenetic friction. These higher levels of kenetic friction allow a driver to slide the tires and maintain acceleration at the same time. If you read any european winter tire reviews you will notice that they all agree studed is better for ultimate grip (average between the kenetic and static friction they can produce) than non.
There are many good studed tires out there, but the best I have used are the Nokkian Hakkapalittas.
This year because of a tighter budget I am running Italian Marangoni tires with aftremarket studs. These are VERY noisy on the street, but give me comperable grip to the Nokkians for half the price.

Width;
If you go narrower; With Blizzaks, you will loose a little ice grip and tread wear will increase, but gain some snow traction. With a non studed ice tire I just stick with stock sizes (on a VW rabbit, honda accord ect.. unless you have exceptionaly wide original tires) With studded tires as you get norrower you will increase the preasure on each stud and therfore increase ice grip, you will improve your snow traction, the only thing that suffers is your pavement traction and wear, but again that's not the point of a winter tire. So for studded tires get as narrow as you can.

Sidewall height;
The tire sidewall is like cushion that helps in cornering. The taller the sidewall the more lateral flex you get from the tire and the easier it is to keep the tire in static friction. Think drag tire deformation, only lateraly. So smaller diameter wheels are best. Here again is a compromise too tall and you lose "feel" I find the 15" wheels are good on our cars. I run 185 65 15. I'd love to find some 165 70 15. 14s would probably be even better but brake mods......

Wear;
Do not apply what you think you know about wear on summer tires to winter tires. On snow and slush, winter tires need to evacuate the snow so tread deapth is very important. On ice, winter tires use the tread height to flex lateraly and maintain stactic friction. I think that generaly people consider summer tires to lose very little grip until wear begins to dip below the 25% remaining mark. IMHO (well not that humble on this topic) a winter tire (especialy non studed) at 50% wear has lost 75% of the added traction that it had (over a 4 season tire) when new, and is therefore trash.

[BAC5.2]

Man up. Get studs.

I have CONTEMPLATED getting a second set of my AT's and studding them (since they can be studded) for winter use. Buying a second set of the 5-spoke 16's and painting them black or something.

Then I really would be driving a tank.

Saddly, it just doesn't snow enough to justify even MORE hardcore tires than I already have. Now if I lived in Colorado or Canada...

My current tires are monsters in everything but bare ice. Everything else, these things eat up.

[dropdfocus]

Phil, your car is a tank reguardless!

[Dynamic Entry]

I ended up buying Gislaved Nord-Frost 5 which come from the factory with studs. They are 205/55 on the '03 16inch wheels and I intend to leave them on there and get '06s with a summer performance tire in the coming weeks.

The Nord-Frost were awesome, my only complaint is that I find it harder to get the rear end to come out when trying top play around. I used to turn around from being parked on my street in one move and this winter I was relegated back to 3 points but of course that is the whole point, these things held to the road.

It was interesting to have studs because it made for some novel vectors on the street, I would take a corner and mid curve my instincts would tell me "okay, here is where the tire will give up and I will slide wide abit - wait what's this, the studs are clinging on for life!"

Biggest actual downside is that Winter Auto-X is so very hard on the tires because we have some events without any snow, just frozen gravel.... I would say about 35% of my studs have been ripped out! The reason I got studs is that last year our course had large sheets of frozen ice that were uncovered when the snow and gravel was pushed off after one or two runs. This year, these ice patches did not form so i think I would have had as much luck at competition without studs. But they came in handy for about 3-5 days of driving in the city.........

[Canadian Turbo]

Sweet Pic!!!!

Well frozen gravel is a whole other factor that I have no experience with.

The Gislaved Nord frost is a great tire by reputaion and rates very well in the credible tire reviews that I have read. Any Volvo dealer will tell you.

As far as getting the back end out to play, have you done anything to your camber?? I put an 04 STI suspension on my car and it handled like a loaded tour bus at 0 camber. Set to -1.5 at the rear was better, but for ice, it wasn't until -2.2 at the rear that I began to feel well balanced. I plan on setting it to -1.5 in all 4 corners when I put mmy summer tires on.

[Dynamic Entry]

*blush* my suspension is stock, but looks like it will become AGX w/ Eibachs soon

as it stands the front camber is "max" and we don't have a cam bolt in the rear...

I may be 0 for a little while

[know1]

bump!

seams like a good time of year to be talking about our snow tire decisions this year.

I'm thinking about getting some hankook ice bears

[93forestpearl]

This will be the fourth winter on my Pirelli Winter Carving set of 205/55/16's. They have a bit harder compound since they are studdable, but it pays dividends in the wear department, especially when you aren't nice to them on dry pavement.


Compared to No Season tires they still rock.