A lot of traffic to my site seems to be landing here when searching for advice on locks. As I did not specifically say what I use in my article, I will list it here.
Firstly, the best course of action is not to lock your bike up outside. If I’m visiting somewhere new in London, I always ask if it’s going to be possible to take my bike inside the building. But if that’s not possible, I lock my bike up like this. I use a very strong D lock on the front wheel, plus frame, and secure it against an immoveable object. Choose what you lock your D lock to carefully. I have heard of thieves cutting railings because they are easier to get through than the D lock and then walking off with the bike.
I use a Trelock thick cable lock for the rear wheel and, preferably, attach this to the immoveable item also. If you’re worried about your saddle and seatpost, you should remove this too. If you’ve got a quick release seatpost, you’re going to have to.
The most important thing you need to remember about locking your bike up in an urban area is that however well you secure it, if you leave it somewhere long enough, someone will try to steal it or parts from it. The shorter you leave it somewhere, the safer it will be. I always try to lock my bike up where there are lots of other bikes as there is some safety in numbers. But, again, this is no guarantee.
Anecdotally, I read that the Met Police set up some honeytraps to catch bike thieves and one bike was stolen within 7 minutes in Hammersmith. I also heard of a cyclist who nipped into a supermarket, secured his road bike with his good quality D lock, spent 15 minutes in the store and returned to find his £1500 Focus bike was gone. A pertinent warning of how quickly your bike can be taken, even if you’re using a decent D lock.
I’m deliberately not going to recommend one D lock over another. There are lots of good quality locks out there. Just don’t buy the cheapest – it will be a false economy. Ask for advice from your LBS.
Probably the best deterrent against getting your bike nicked is to buy a really rubbish one to use in urban areas. I don’t have room to store more than one bike but if I did, I’d buy another one for this purpose.
I realise much of what I have written is probably plainly obvious to most people but I thought it would be worth stating for the record. I welcome comment and observations from other cyclists.
UPDATE: This interview with a former bike thief is essential reading.