D-Locks Guide
Overview
For use in medium to high crime areas
A D-Lock (also known as a U-Lock) is the most practical bike lock you can get for peace of mind when you’re at the shops or in work all day.
D-Locks are ideal for bike security as they offer strong protection against a range of attacks. While some of these locks will be heavy, they are much more portable than a chain lock and far tougher than a cable lock. D Locks are very stiff meaning they’re easy to fit around your bike and a stationary object.
Most D-Locks come in two parts. You have the shackle made of steel or hardened steel with a diameter up to 18mm. The crossbar contains the locking mechanism and you slide the shackle into the bar and turn the key to fix it in place.
Size
D-Lock Size
A standard D-Lock will easily fit around your bike and normal bike racks. If you have a particularly wide framed bike you can get wider and longer shackles. Alternatively, there is also a range of mini D-Locks are that specifically for use just with a standard bike rack. You won’t be able to fit your bike around a lamppost with a mini.
For security, it is best to get a D-Lock which will fit your frame and stationary object without leaving too much internal space. A common way for thieves to defeat your D-Lock is by slipping another object like a crowbar inside the shackle and leveraging with enough force to break it open.
Shackle Diameter
When choosing a D-Lock, the thicker the shackle diameter is, the more secure it is (especially against bolt cutters). However, the trade off is weight. Some very sturdy D-Locks can weigh over 2.5kg. One tip is to lock your bike high on the frame and off the ground to make it harder to use bolt cutters.
13mm & Under:
Under 13mm shackles can be cropped with most standard bolt cutters while some determination.
The quality of steel used in the shackle can increase the time this takes. Ideal for quick visits to the shops.
13mm – 16mm:
At this diameter it becomes much harder to crop a D-Lock with a standard bolt cutter.
Good for locking to the bike rack outside the office.
16mm & Over:
With a shackle this burly only the largest bolt cutter jaws with sustained effort with crack through.
It’s unlikely a thief will have the time or tools to cut through. Great for locking your bike overnight.
Locking Mechanism
Deadbolt Locking
Most D-Locks will now use a deadbolt locking mechanism. A deadbolt cannot be moved to the open position except by rotating the key.
Look for a double deadbolt for enhanced security. This means there is a locking bolt on both sides of the crossbar. Locking the shackle on both entry points greatly improves twisting and cutting resistance. Even if a thief cuts through one end of the shackle, it’ll be much harder to twist the shackle out of position.
Some brands even offer quadruple deadbolt systems which lock the shackle to the crossbar in four places for maximum resistance.
Construction
Lock Material
Almost all D Lock shackles and locking mechanisms are built out of steel. However, some locks will be constructed from hardened steel. By tempering steel if becomes harder and less brittle making it much tougher to cut through.
Sold Secure Rated
A great way to determine the quality of a bike lock is to see if it is Sold Secure Rated. This is a third party, UK independent rating system for bike locks.
Sold Secure Bronze
Coverage: Up to £500
Sold Secure Silver
Coverage: Up to £1,000
Sold Secure Gold
Coverage: Over £1,000
An approved lock is graded as Gold, Silver or Bronze. The rating is chosen by how long it takes to break the lock and the tools needed to break it. If you're planning on insuring your bike, many insurers will state you need a Sold Secure rated lock to make a successful claim.
These values vary between insurance providers so check the terms and conditions of your provider.
Mounts
If you commute to work or use your bike daily, then having a mount to fix your lock to your bike frame is a great way to improve portability. Many brands will include easy to use frame mounts with their D-Locks but check the product description first.
Frame Protection
D-Locks with vinyl covers, moulded end caps and rubber coatings all ensure that your bike frame is safe from scratches and damage to your paintwork.
