The Abus Granit X-Plus has long been among the best D locks on the market, it has a Sold Secure Gold rating and it's not hard to see why.
The shackle is made from 13mm square section hardened steel, and locks at both ends to the base. It has pointed ends which extend right through the base to protect against attacks from jacks, and the square section is intended to make it harder to twist or crop.
You can get the Granit X-Plus with a couple of different mounts, ours came with the TEXKF frame mount that has a positive locking action and secures via a webbing strap. You get two keys too, one with an LED bnuilt-in so you can find the lock in the dark, a useful touch.
There are two lengths, with either a 230mm U (£89.99) or one that's 300mm long (£99.99). The longer lock is more versatile in that you'll find more things that it will easily reach, but it's heavier and more awkward to carry. For lesser D-locks we'd also worry about the longer lock being gappier and therefore harder to fill to prevent a thief getting a jack or big crowbar in there to pry it open. However, the Granit X-Plus resists that attack well enough that we think you can safely choose the longer U if you need the length.
We gave it a good go (five minutes of serious abuse), but to no avail: we couldn't break this one with our standard thieves' armoury. The shackle is super stiff and no amount of cropping, twisting or thwacking would do any serious damage. the plastic sleeve got a bit mangled, but that was about it. Some meaty blows to the base broke off the plastic covering, but only to reveal a serious-looking steel plate construction that does a very good job of protecting the lock mechanism and was dismissive of our efforts. After all the violence was over the lock was still in perfect working order; even the plastic cover just snapped back on.
As we've said, we used all our standard kit on the Granit X-Plus and it came through unscathed. We didn't go the whole hog though and use the 'extreme' kit — one of the latest generation of battery powered angle grinders — simply because we know that the outcome would have been a broken lock. We know of no D-Lock that will currently withstand assault by power tool.
No doubt the lock manufacturers are on the case to rectify that. However it has always been the case that given time and sufficient fire power a really determined thief will get your bike. Luckily there are few such thieves about and locks don't give in quietly when attacked with an angle grinder.
It's a really excellent lock, this. It's not even that heavy for the amount of protection it provides. Unless you live in a real crime hotspot it should give you all the protection you need.
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Excellent level of protection from a well-designed and capable lock.