How to crack bicycle shackle locks

Tech/opinion, September 18, 2004

There's been an almighty kerfuffle recently as a very simple technique for attacking certain U-locks used to secure bikes has been rediscovered and broadcast across the Internet. In short, the cylinder-key locks used on many U-shaped bike locks can be opened with nothing more sophisticated than the barrel of a ballpoint pen.

Thing is, as my old mucker Carlton Reid points out here, this is nothing new. This technique was well-known in the early 90s, in the UK at least, as being a standard form of attack on many cheap Taiwanese locks. I was at Mountain Biking UK magazine when we ran a piece on the problem, and on how amazingly easy it was to open many locks with brute force techniques that, though crude, were fairly easily concealed.

At the time the guy making lots of fuss about this was a bloke from the Midlands called Brian, who had found himself living in a run-down area of his home town, and after having a bike stolen, got talking to the local criminal element who were keeping themselves tidily in beer and dope money nicking bikes. Brian learned their techniques and demonstrated them to us on a range of locks, all of which eventually broke.

Interestingly, none of the locks in that test - one of which was a Kryptonite, the maker of the locks at the centre of the current fuss - could be opened with a pen. Brian had managed to hound most such locks out of UK stores by complaining through his local Trading Standards Office. A couple of years later I came across one that could be opened in this way - a cheap Taiwanese lock bundled with some steel widgets that filled the gaps in the lock, making some forms of attack much harder.

In the piece we ran in Mountain Biking UK we didn't detail the attack methods Brian demonstrated. I argued that we should. In my view, the bike thieves already knew them and we owed it to our readers to inform them of just how trivial it was to open many of the locks on the market so that they could make informed decisions about what to buy.

I was over-ruled. At the time, Mountain Biking UK regularly copped flak from the industry for showing people jumping around and being silly on mountain bikes. The sort of thing you now see in adverts from, oh, every mountain bike manufacturer - but now the marketroids call it 'freeride' so it's okay. Telling people how pathetically insecure their locks were, and exactly how they could be breached, would be irresponsible. So the article on Brian's lock tests was rewritten to hide the exact attack techniques used.

Twelve years later, I still believe that knowledge is power, and that people really should know what attack techniques thieves use on bike locks so they can make informed decisions. Here, then, are the lock attack methods we were shown back in the day.

1 The pen attack

I won't waste time describing this in detail as there are video clips of it all over the net now. Bikebiz has a good collection of links to them. It does seem to be only locks manufactured in the far East that have this problem. Kryptonite's lock in the 1992 MBUK test could not be opened in this way. My guess is that there's one or more lock mechanism makers in Taiwan or China, producing very cheap cylinder-key lock mechanisms that are susceptible to this attack.

2 The screwdriver trick

This one is simple but time-consuming. You take a good quality hardened-steel screwdriver and use it to pick out the metal face around the lock mechanism. Eventually the lock falls apart and the shackle can be opened. This is easily defeated by hardening the metal round the lock and using plenty of it, but both those manufacturing steps cost money that's just not available when you're aiming for a sub-US$30 price point.

3 If I had a hammer...

Many shackle locks have brittle lock housings or lock mechanisms. Brace the bottom of the U against whatever the bike is locked to, and hit the cross-bar good and hard with at the lock with a hammer and they'll pop open. This method's not subtle by any stretch of the imagination, but you'd be surprised at how passers-by just don't want to get involved with anything dodgy-looking. Back in my bike shop days a colleague and I spent 20 minutes cracking open a shackle lock (at the owner's request - the lock had jammed, and we had no idea what we were doing which is why it took so long) in the middle of the rush hour, right next to Leeds railway station. Literally thousands of people must have walked past us. None of them asked us what we were doing.

4 Let's twist again

Brian had some special equipment for this one: a long steel bar (somewhere between 18 and 24in if memory serves) and a similarly long thick-walled tube that fitted over it. Braced across the legs of the U, this provided enough leverage to twist most shackle locks like taffy. Good locks will tolerate this because they have a ductile core inside a hardened outer, and because both ends of the U engage firmly into the lock. But if the U is brittle or the lock mechanism doesn't engage it properly, things will break. If you think this attack is too obvious to get away with in the street, consider how easily a a couple of pipes can be hidden under a long coat...

The wider the U, the better the lock resists this sort of attack, because the pry bar has less leverage if the legs are far apart. Narrow U-locks, as well as being harder to use because they fit round less street furniture, are therefore less secure.

Top lock tips

Notice what's missing from this list: bolt croppers, hacksaws, drills, car jacks, freezing sprays, picking - all those clever-clever attacks that manufacturers like to claim their locks resist. Problem is, bike thieves don't go in for sophisticated techniques like those because - let's not beat around the bush here - bike thieves are morons. Your typical bike thief is a lowlife scumbag who just wants to turn your precious bike into enough cash for a few beers, a lump of hash or his next fix. He therefore goes for techniques that are quick, hard to spot and involve tools that won't get him busted for going equipped.

Fortunately, those techniques aren't too hard to defeat. For starters, many of them rely on being able to get something through or inside the lock to exert force on it. Fill your lock with frame members and wheels when you park it, and there's nowhere to put a pry bar or hammer.

Then there's attacks on the lock mechanism and cross-bar. The way to defeat these is to lock your bike to railings so the lock mechanism is inaccessible, rather than to, say, a lamp post which allows a thief 360-degree access. Admittedly that's not always convenient, but neither is getting your bike stolen.

Oh, and any bike thives out there who resent the above description, please get in touch. I and a few friends who have had bikes stolen would be delighted to hear you plead your case. We promise your subsequent stay in intensive care won't be too lengthy.

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