Chain locks are not all that great. Ive had to break a few chains in my day to get them off used bikes ive bought at yardsales. 2 long heavy screw drivers one in one link one in the other. Then you just twit the 2 links till one breaks. Also make sure your cable type locks are good ones dont get cheap look alikes. Cables can be broken by twistign the cable backwards of its normal twist. If each wire is thing a pair of what most call dikes (diagnal cutters) can then be used to cut a wire ot 2 at a time. On cheap cable locks a pair of toe nail clippers will work to. If you realy want to be secure nothing beats a u lock and good cable. Use the cable to run through your rims and u lock to lock the frame to a pole.