If you’re going to be leaving your bike unattended in public for any period of time then it is definitely advisable to invest in a good quality bike lock. It may be tempting to buy the cheapest lock on the market but the sad truth is that bikes are a prime target for theft and the most determined thieves will make quick work of removing an inferior lock. There are 2 main types of bike locks, each with their own pros and cons:
Cable locks offer flexibility and convenience due to their light weight and compact size when looped around themselves. These qualities make this type of lock perfect for commuters as they won’t add a bunch of extra weight to your ride. However, cable locks with a cable gauge below 14mm can be cut by standard bolt-cutters so if you’re going to be leaving your bike in a less than desirable area you may want to consider going with a U-bolt lock for extra peace of mind.
Generally a cable lock with a key lock will be slightly more secure than one featuring a combination lock however should you lose your key you’ll be wishing you went with a combination! (most do come with a couple of spare keys though).
Also known as D-bolt locks, offer the best protection when it comes to locking up your ride. They are generally made from solid hardened steel and feature more robust protection around the locking mechanism. U-bolt locks are heavier and less compact than cable locks however the added protection they provide is worth carrying a little more weight on your commute.