Saturday, January 26, 2013

Winter Mode: Activate!

Mach V BRZ in Winter Mode
This blog has been quiet for a couple of months, but that doesn't mean we haven't been busy.  Obviously the BRZ wasn't meant as a snowmobile, what its low slung stance and rear-wheel-drive, but we think any car can be fun and useful in the winter, given the proper equipment.  That means winter tires.  We picked up a set of lightly-used Legacy GT wheels (17x7 +53) with some Blizzak WS60 tires in the stock BRZ size of 215/45R17.  It doesn't really snow that much here in the D.C. area, so we held our breath each time cold weather came around, but we didn't actually put the snow tires on until the snow was falling this past week.

Blizzak WS60. That snowflake means "Let it snow!"
The stock "performance" summer tires aren't what we'd call super-high grip in the warm weather, but they're next to worthless once the temp drops below about 40 degrees F.  The same is true for our Dunlop Direzza Z1 Star Spec track tires.  The Blizzaks, on the other hand, seem to work the same no matter how cold it gets.  That's not to say they're a great tire when it's warm.  The soft tread compound combined with the deep siping cut into each tread block means the dry-weather grip is very low.  We noticed some wheel spin just turning through an intersection -- something that never would have happened with the stock tires.  The tire feels normal in terms of sidewall stiffness and steering response, but the limits of adhesion are very low.

Who says you have to leave the sports car home when it snows?
Then it got cold, and this past week we finally got some snow.  The performance of the WS60 in the slush, snow, and ice, was a revelation.  In particular, braking performance is so good on packed snow or ice, it's hard to believe.  It feels about the same as driving the car on wet pavement.  It's amazing!  I found myself just doing braking tests anywhere I could find snow on the road, just to be astounded all over again.  Acceleration and cornering aren't quite as dramatic an improvement, but still are far better than any all-season tire we've ever used.  (Our 335i is currently shod with Continental DWS, so that comes to mind for an immediate comparison.)  I found myself thinking it would be a lot of fun to throw some skis or snowboards in the back and drive up to the mountains.  (For deeper stuff, factory ride height would probably be a better choice than the Mach V springs we've got on the car.)

That special Blizzak tread compound has a spongy composition that Bridgestone says is made of "thousands of microscopic tubes and cells (which resemble the consistency of Swiss cheese when examined through a microscope)". The tire tread can wick away water that would usually come between the tire and the snow or ice surface. That same light and fluffy compound isn't so resilient in the dry, though, so if you drive these tires around on dry roads for thousands of miles, the special tread compound will wear off. The manufacturer says at half tire life, you only have 10% left of the magic snow tread stuff.

Speaking of wheel and tire swaps, we've been experimenting with some different wheel and tire sizes to fit the BRZ.  I'll have more details in my next blog post.