The only thing I use is a wheel lock normally, but if I'm in a rough neighborhood, I bring a Kryponite chain for the wheel to the swingarm in a backpack. I know people will still be able to carry the bike away. If they are that determined, then chaining it down may not prevent them much either, if it even slows them down much. I carry a backpack most of the time anyway from either books or clothes or whatever I need to drink. Just my two cents....