Defeating Your Own Bicycle Locks
 

The issue of bicycle locks is complicated by the need to defeat your own lock if for example as in my case, the combination no longer works (happened to me once before when 1515 became 2515 but I got that by trial and error - caused by knocking the switch that lets you change combination). Anyway, a hacksaw was USELESS for my cheap £5 lock which was constructed of many steel cables woven together. However, after two chops with a pair of big bolt croppers, the lock yeilded and my bike was free. Whilst this was pleasing at the time, and would be in a similar situation in the future, I suppose you've got to balance it against other people getting in.

Would a D lock be so susceptible to bolt croppers? I've heard of D locks being defeated with a biro (flawed key design)! I was wondering what ways different locks were defeatable. For example, there are £100 kryptonite chain-based locks available - which is the weakest link (the chain or the lock) and what would it take to break it? Can anyone advise which locks are good against and which are weak against different methods of breakage?

If you couldn't get into to your own fancy expensive lock, would you have to pay the fire brigade to use the jaws of life? And how much would that cost?

Maybe at the end of this discussion, a sticky could be posted advising which combination of locks to use.

I have had to cut locks on a couple cheap bikes I have bought.

First was a cable lock which I used a pair of tin snips to cut through. Second was a chain lock which lasted about 90 seconds against my Dremel tool. I am sure a thicker D lock would take longer, but any metal cutting tool could still get through.

Locks are a deterent, not a prevention tool. If someone wants to steal your bike bad enough, they will find a way. Lazy theives will go after the unlocked or thin locked bikes. Pros will take the good stuff and are very skilled at defeating anything you can use to lock them down.

I once lost my key to my padlock down the outhouse, and had to defeat my cable which was something like this one:

http://www.nashbar.com/nashbar_photos/medium/YY-HWL.gif

I simply laid the cable against a rock with a sharp corner and bashed it a few times with a rounded rock, and the cable was pulverized.

For the heavy-duty locks that you're asking about, an oxy-acetylene torch is the fail-safe answer, and probably cheaper to hire than the fire brigade. Nothing is going to hold up to 3000°C temperatures for long.

As for practical locking strategies, I like the idea of using two categories of locks that both have at least modest resistance to offer. A U-lock or D-lock, combined with a good chain lock, means the thief has to be equipped to take on both varieties in one sitting. Since you appear to be in the EU, look at the Abus Steel-O-Chain 810 as a secondary lock, plus a good D-lock/U-lock as your primary. If you lock in the same place every day, you may be able to leave one lock there to save having to carry it along all the time, while keeping the other with you for random usage.

Does the biro thing extend to the kryptonite new york ev disc lock?

Angle grinder with cutoff wheel.

No, because they changed lock-cylinder designs. The one in the attached photo is the vulnerable type.