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, Sun, 12 Dec 2010 11:12:16
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The brand new grand touring tires on AWD should be able to get you through most snow conditions in the first 15k-20k miles of driving. It's when the tread depth is down to 7/32" or less that you have to consider other tire options.
People are often carried away by the nominal names like "snow" vs. "all season" when in reality the snow/ice patch contacting your tire does not know one wit about the marketing name of your tire, nor does it care. What provides traction in snow/ice on the contact patch are the following factors:
1. Tread depth. Tread depth is what grabs onto snow and mud when stopping or starting. All season tires vary widely in tread depth even when new. Some have as little as 8/12" tread depth when new, some as much as 12/32. They obviously perform significantly differently, especially after being use a season or two. By the same token, one really should not be driving around in the snow with less than 6/32" tread depth, regardless what type of tire one is driving. I make 7/32" as my line for switch over at the beginning of winter; I can swap the wheels mounting 7/32" tires back on in the spring, and wear them to about 4/32" before discarding the old tires altogether.
2. Sipes. These are the numerous tiny cuts made onto the tread blocks. These are what bite into ice when stopping or getting going. Some all season tires have numerous sipes just like snow tires do. Sipes do not go all the way to the root of the tread blocks. That's another reason why one should not drive around in the snow with less than 6/32" (or even 8/32") tread even if the tire was originally marketted as "snow tires."
3. Tread Compound. More than a decade ago, the general rule of thumb was that snow tires used softer compound, trading tire longevity for low-temperature traction; the downside was of course that snow tires would wear away very quickly when outside temperature is above 50 degrees. What emerged a decade ago was silica/silicate compound in tire making. What it essentially provides is microscopic "sipes"/biting-teeth at crystaline level. Those first made appearance on studless snow tires like the Blizzarks, which enabled the first 1/4-1/3 of the tread to provide multiple times the traction of regular soft-compound winter tires; the difference was so significant that Bridgestone had to give warnings about the last 2/3 of the tread on Blizzarks are just regular old winter tires with much less snow/ice traction. At the same time, the first 1/3 of the Blizzark treads (and follow-up competitor entries) practically made studded winter tires obsolete. In recent years, that silica/slicate compound technology has moved to all-season tires, resulting in all-season tires that can literally beat snow tires (of lesser silica/silicate treatment) in snow/ice traction when they are relatively new. On top of that, one does not have to deal with the dilemma of when to put on the snow tires when the outside temperature fluctuates in December.
A year or two from now, when your 10/32" ProContact tires are worn down to about 8/32" or 6/32", it will be time to decide whether you need a new set of snow tires or a new set of all-season tires (of then cutting edge technology) mounted on perhaps 17" wheels for winter, and use the 2nd 1/3 of the tread life of your existing tire for warmer seasons. The last 1/3 of the legal tread life (4/32" to 2/32") is not very safe to use unless your driving environment rarely has rains.
posted by 96.233.42...
, Sun, 12 Dec 2010 11:12:16
, Mon, 13 Dec 2010 17:19:28, Mon, 13 Dec 2010 11:48:02
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