Put a trainer tire on it unless you want every one of your neighbors to hate your guts. Trainer + knobby tires is super loud. Assuming you're going for a traditional trainer that places a drum against your tire and not one of the expensive ones that mount to your drivetrain. Your best bet for reasonably priced yet good trainers are the Kurt Kinetic Road Machine and CycleOps Fluid2. If you have much more than that to spend, you may be able to swing one of the drivetrain ones (I think the LeMond revolution, for example runs around $700).