kchunks

As the thread title indicates this is going to be my first winter commuting by bicycle. I recently moved to Missoula, MT, and don't know how bad the winters are going to be. From what I hear, they are cold, but not too much snow. I am told that any typical morning snow has melted off of the roads by the afternoon. Anyway, what do I need to prepare for? I have some idea about clothing but I don't know about the rest. I read these stories of freezing brakes and deraileurs, how serious is that problem? Are studded tires necessary? My commute is about 7 miles each way over relatively flat terrain.

kill.cactus

I'm going to guess that you're looking at high twenties overnight averages for the most part and then warming up to the mid/high 30s during the day from your description.

Bike:
I wouldn't worry about your stuff freezing/getting destroyed on your short 7 mile commute. But remember that if you're on roads that are deiced or treated with salts to make sure you keep your bike clean and oiled. You may just want to get a cheap (but in good order) beater bike to use. Put some knobby tires on it, just in case, or until you figure out what the winter is like and can adjust appropriately.
Need: fenders, knobbies, beater (or a bike you will take GOOD CARE OF b/c of the salt and crap)
Nothing really more.

Clothing:
Clothing wise, as long as you're biking above 20 degrees F, I'd suggest putting on a base layer consisting of some wicking fabric. I generally use just some tight fitting athletic clothing. Put a thin fleece over your base and on top of the fleece, put a windproof (proof, not resistant) shell. Try and get this shell to be waterproof as well.

If you're cold when you start, that is normal. If you're cold by the second mile, it means you need to put on another thin fleece. That should keep you happy

Others will give you more detailed advice. I ride 4 miles to school and I'm going to do it through winter. I believe that riding in winter is really something you can apply the KISS rule to: keep it simple stupid

kchunks

Thanks, Cactus. I love outdoor sports in the winter and I think I can get the clothing thing down fine. I had just read things about people with freezing brakes and other things that had me in a quandary. I appreciate the advice on the knobbed tires. I switched to touring about a year ago for fair weather commuting and have loved them. I guess that when the snow flies I will get those knobs out. Do people normally run the recommended PSI or lower it for winter conditions?

Sixty Fiver

I run lower tire pressure in the winter to get better traction and ride and I have a set of studded tires mounted on other wheels if it gets really icy.

My winter bike is a fixed gear mtb and presently has some semi slick tires on it as they offer a greater contact area on icy patches and good side knobs for off camber traction in snow.

I have found that the tire's compound (soft vs hard) plays a greater role in how well they hook up than the tread as knobby tires just don't bite into ice and have a smaller contact area.

For really icy conditions studs are the way to go... I make my own and don't stud the centre as centre as I really only need extra traction when the bike is off camber.

Machka 

Mainly ... expect to be slower.

Also, if you don't get much snow or ice, you don't need studded tires.

CastIron

You will be slower. None of us have come up with a really solid, specific reason, it just is.
It's not as bad as many think. Fact is, it can be a dawdle when you least expect it.
A handful of days will really, truly, suck.
You need more lighting that you think. Especially rear blinkies.
Always--always--carry an extra layer.