Chain Bike Locks
Reinforced steel chain locks offer added protection from theft. A steel locking system that is 3/8-inch thick can resist cutting, drilling, scratching, coiling and freezing. Heavy duty models feature large and bulky chain links that are welded together to prevent thieves from gripping the chains with a cutting tool or separating the links with a chain spreading tool. The locking device can be a bolt-type lock or standard lock. A key is necessary, and not all manufacturers produce a master key to offer added security against copying. Chain locks can be attached to a front or back wheel and secured to a post when parked. The chain is covered with plastic or an inner tube to prevent damage to your bicycle. Standard sizes range from 3 to 4 feet when fully extended.
Cable Bike Locks
Cable bike locks are made of steel and feature an integrated combination or key lock. A built-in miniature light can make reading the combination pad easy. High-quality brands offer maximum protection against pick and pull attacks. The thickness of the cable and level of reinforcement will determine the level of protection against cutting. A self-coiling cable lock is easy to carry, and can be fastened to the upper frame of your bike and allowed to hang freely as you cycle. Cable locks easily thread through the frame and wheels of any bike, and can be attached to a post when parked. A vinyl cover offers protection against scratches and damage to the frame and wheels of your bicycle. Thickness of the cable can range from 6mm to 18mm.
U-Locks
U-locks are sturdy locks that have a "U"-shape design. A cross bar connects to a shackle that detaches with a key. Locks designed with a key hole on the bottom are generally more durable than those with a key hole on the side. Keys that must be inserted from the side are more prone to damage. Reinforcement bars and collars are available for added protection against theft. Reinforcement devices fill gaps that may be penetrable by a thief with a crow bar. Standard bicycles generally require a 14mm shackle.