D-Locks are generally thought
D-Locks are generally thought to be best – I have a “Magnum” mini (also sold as the pitbull mini) with a cable (the cable secures my QR front wheel). Cost was about £36ish from Halfords.
The key to using a D-lock is to fill the shackle with bike and stand. This is because they’re normally broken with bottle jacks (so the thief has to have space to place the jack inside the shackle). It’s easier to fill a small shackle than a large one, hence my preference for a “mini” lock rather than one with a big shackle.
Sheldon Brown on lock strategy;
http://www.sheldonbrown.com/lock-strategy.html