The typical u-lock weighs around 1 300g. A typical 10mm cable lock weighs around 600g. The former slows down a knowledgeable thief by a minute or two, the latter by a few seconds. Almost any lock will stop the casual "thief of opportunity," the jack-ass who steals a bicycle because it's unlocked. In my search for a viable locking mechanism, I stopped looking for strength in favor of a lock that would produce noise, and lots of it. At first blush, lap-top locks, which have 1,5mm - 3mm cables, seem to provide almost no protection. If the cable is cut or if they are jostled, though, all hell breaks loose. My lock gives a warning beep after 4-seconds of movement. At 8-seconds it will scream out 95 deciBells of the things thieves hate most -- noise and attention. My partner's DefCon did the same, but hers went to 11 (Bells).
Though they both weighed around 165g, my DefCon 1 Ultra was different in important ways from my partner's DefCon 1. The Ultra has four permutations, the 1 has three; the Ultra has a 90cm long cable, the 1's is 120cm; the Ultra has a 2,4mm thick cable, the 1's is 1,8mm. The volume of noise was also significantly greater in the 1.
I preferred the 1 to the Ultra. Having a 120cm long cable allows one to lock the front wheel to the frame and to the object being locked to. In order to spool the 120cm of cable in the same size container as the Ultra, it has to be thinner, but this is not a draw back. The cable isn't so much about resistance to cutters as it is about deterrence. The greater volume of the 1 is something I prefer. The only deficiency of the 1 is the number of permutations. These locks are notoriously easy to pick, so anything to add jostling time (which triggers the alarm) to the would-be thief's efforts is important.
Though this lock is an excellent way to provide security without a weight penalty while touring, our locks had trouble. The primary trouble is that they are not weather-proof, particularly the Ultra, so a night or two in the rain and my alarm stopped working. The locking mechanism still worked, and the light still blinked, but that is small solace when the primary deterrent stops functioning. My partner's lock continued to work, but at least once gave off false alarms -- we had the bicycle in view and the lock went off. We thought it might be the wind jostling it, but that proved incorrect. It now works again, but it is troubling that it inexplicably stopped working properly.
