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Bicycle lock


A bicycle lock is a security device used to deter bicycle theft, generally by fastening the bicycle to a fixed object, e.g., a bike rack.

Quick-release levers - common on most bicycle wheels and seatpost fasteners - are a major challenge for theft preventions. Unless both wheels and frame are secured, wheels can be removed separately. An optimal locking method will secure the frame as well as both wheels — either to a fixed object or to each other.

Locking devices vary in size and security; the most secure tending to be the largest, heaviest and least portable. Thus, like other security equipment, bicycle lockers must balance the competing interests of security, portability, and cost. Some are made of particularly expensive materials chosen for their acceptable strength and low density.

An alternate defense is the provision of bicycle lockers or a bike cage in which the whole bicycle is locked, but these are uncommon in some countries. A bike locker is not a bicycle lock.

Test standards that rate the effective security of bicycle locks are provided by Thatcham and Sold Secure in the United Kingdom, ART in the Netherlands, SSF in Sweden, and VDS in Germany. Tests carried out by the Cyclists' Touring Club showed that all of the locks under test could be broken in less than 42 seconds using either bolt cutters for a cable/chain or a bottle jack for D-locks.

A U-lock is a rigid metal ring in the shape of the letter U. The U part of the lock attaches to a crossbar section, and for this reason they are also called D-locks. To lock the bicycle, one locks it physically to some other object, such as a bike rack, parking meter or other pole installed securely in the solid ground. Merely locking the bike frame to the wheel is not recommended because, although it cannot be rolled away, the entire bicycle can still be lifted and carried away.

U-locks are more secure than most other kinds of locking mechanism because they are more resistant to cutting with high-leverage hand tools such as bolt cutters. However, most are still vulnerable to at least one type of exploit. For instance, if there is enough space for a thief to fit a jack into the U, the jack can produce enough leverage to break the lock. Another common brute force method to break open U-locks is to use a long length (perhaps 2 metre) of pipe to twist the lock open (although this method is more commonly used to defeat chain and cable locks). Like all locks, U-Locks are vulnerable to power tools such as portable angle grinders. A quality U-lock will advertise the material's hardness (relative resistance to grinding), its resistance to prying (expressed in tonnes, or pounds, for example, one might resist to 5 tonnes, which exceeds the 2-tonne capacity of a common car jack), as well as resistance to drilling into the keyhole itself.


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