In Central Alaska biking is a challenge in the Winter. My wife and I have mountain bikes with studded tires for icy conditions and we have Pugsley bikes with fat tires. You may be able to find a cheap mtn bike to use. BUT...we also enroll in spinning classes. The most important thing is the things that are the same...like the ability to get a good aerobic workout and to work the muscles that are biking specific. One huge downside to many spinning classes is the lack of a breeze...they bring fans to ours but it's still a sweat shop. Spinning bikes also give a false sense of what it's like to stand and hammer. The moving flywheel makes it seem easier than it is when you're on a bike. All said and done they are a great way to keep in bike-shape for the summer.