Some bad people may want to steal your bicycle... Dont let them! Keep them at bay with a bicycle lock.
A good lock will deter all but the most determined of bike thieves.
A widely quoted 'rule of thumb' is to spend 10% of the value of your bike on your lock.
Bike Lock Ratings
Bike lock manufacturers such as Kryptonite and Abus give their locks a rating to indicate strength, usually a number. A higher bicycle lock rating means a more secure lock - able to withstand a longer attack with heavier tools ...
Your insurer may insist that your bicycle lock also has a 'silver' or 'gold' rating - these are the best bicycle locks you can buy...
Read the description of the lock, product descriptions will always mention silver or gold ratings.
Buy a D-Lock and a wire-loop lock to allow you to lock your front wheel.Always try to lock to something secure like a cycle-stand or railings.
On a long ride or a cycling holiday carry a lighter lock - something to deter an opportunist from riding off on your bicycle.
When you park, remove your bike lights and accessories and take them with you. Replace your saddle quick-release with a bolt to stop some toe-rag from nicking your saddle.