I went down to 15inch... I believe the tire size is 195/65/R15 (or was it 195/60/R15). I have the Dunlop Graspic DS-1. I wanted to get the Michelin Arctic Alpine instead, but they were already sold out by the time I got around buying my tires.
The reviews on
www.tirerack.com said the Graspics are better on thick snow, but the Arctic Alpines are good for more icy conditions. For city driving, I think icy conditions is more applicable.
I haven't tired other winter tires before, but I think the Dunlop Graspics are pretty good. When I first got it last year, I drove to Toronto on 401 and I was going 130 - 140 with snow on the ground. That's the same speed I go during summer. I didn't slow down until I saw a couple of SUVs in the ditch near Kingston.
Oh, the Dunlop Graspic DS-1 only has a speed rating of Q. But I think the Alpine has a H speed rating.