It kind of depends on what you mean by 'winter'. On the West Coast, you think it means rain, so I am not speaking with you; here in Tokyo it is the driest riding of the year. I am talking about winter that gets snow, in cities where it is more or less well cleared. In Toronto, I keep my fixed gear on its standard tires in the winter, because there are plenty of days without ice or snow. Other days I can't keep rubber down that way, and I have experimented with all three of the following options, except the last.
I don't like them. They do what they are meant to do, but they are noisy on pavement and slow. Also play hell on any tiles or linoleum where you might store the bike.
Wide Tires at Lower Pressure
fat-tire specific frame, they'd be slow on the road too, but that's not what you get them for. You want them if you live in a place like Toronto: the snow is not reliable enough to get nordic skis, the city park paths are not ploughed for regular bikes, and the roads are poorly ploughed for days at time. Boo hoo, that ain't going to stop these tires! Bonus: nothing can stop you summer, either.
Wait! How many bikes is that?
You're not going to try switching tires or wheel-sets on the same bike, depending on the weather. Tried it: too much trouble. I won't tell you how to spend your money on how many bikes either. I will tell you what I'd do.
- One bike: have the cyclocross tires on it, as they are most multi-purpose.
- Two bikes: that bike, and one with normal tires for dry days; or with the fat-tires if you have a lot of snow, or good trails!
- Three bikes: one each fat, cyclocross and normal!
I should credit this blog's post, for the inspiration.
Drivetrain - I hate 'singlespeed', but love fixed. Either saves tonnes of trouble in the winter. On the other hand, I run derailleurs on one bike through the winter and have had little trouble with moderate care. Forget STI shifters with warm gloves. Old style bar-cons work fine.
Fenders - Yes, of course. Means you can forget a frame with tight clearances, unless you want to kluge something, as I have done. Much like this. Done similar on my Kona Paddy Wagon, but will be buying the right bike when I go back to Toronto.
Lights - Another post, here.
Pedals - From experience, clipless pedals are only for dry days. Days with snow and ice means you'll need to 'dab' with your feet, and quickly: studded wide platform pedals. Some go for plastic, because it does not conduct the cold so badly. I just wear thicker soled boots those days, with winter insoles.
Clothing - Everybody has a post on this. I can summarize my approach: layers, wool inside, 'soft-shell' outside, neoprene shoe-covers, pay real money for gloves, and consider goggles.