There is no lock on a bicycle that cannot be broken, but if you have a strong lock and a good locking method, there is a far lower chance that your bicycle would be targeted by thieves.
U-Locks
This type of bike lock is very popular since it is an effective deterrent. Hammers, chisels, and other similar tools are unable to penetrate the robust locking mechanism. Its horseshoe form can prevent leverage, provided that it is not significantly larger than necessary for the bicycle. The objective is to lessen the amount of room available through which a burglar may maneuver a crowbar and generate enough force to pry the object apart.
There is a range of sizes available for U-locks. Your objective is to determine the correct dimensions for the lock so that it can encircle the items to be secured with the smallest feasible gap. Models that are small to medium in size lock one wheel as well as your frame to a stationary object. The large variants will lock both of your wheels as well as the frame to a stationary object.
Cable Locks
These locks are versatile and adjustable, although in general they provide a lower level of protection against theft than U-locks do. The vast majority of cable locks can be broken through with bolt cutters. On their own, they might be appropriate for use in locations with a low crime rate. In other contexts, they are an excellent choice for usage in conjunction with a U-lock to secure components that can be quickly removed (e.g., seat). Many are equipped with key or combination locks built right in, while others call for a separate padlock. A few of them have a sliding sizing, while others have an armored coating. A handful of the more recent models sport fashionable layouts.
Chain Locks
These bike locks feature a specially designed chain link that is resistant to hacksaws or chisels and makes it difficult to leverage the chain. They are durable enough to be used in locations with a high crime rate. Thieves can simply cut through thin locks, regardless of how sturdy the chain is; therefore, you should make sure to purchase in a padlock that is just as sturdy. What’s the catch? Because of their weight and size, chains are most useful when employed in applications that are not mobile.
Locking Wheel/Seat Skewers
Unfortunately, thieves find the same convenience in quick-release wheels and seatposts that bike owners do while riding their own bikes. Locking skewers block the quick-release mechanism, making it significantly more difficult to steal, and are therefore ideal for high-crime locations. The installation is simple, although some of them call for a specialized wrench that is included with the skewer.
Bike Lock Keys and Combinations
Flat keys or cylindrical keys are used in keyed locks, depending on the kind of lock. In previous years, when it was discovered that some locks of this design could be picked with a ballpoint pen, cylindrical keys gained a poor reputation that has stuck with them to this day. Because more recent models have addressed that issue, you can now choose either fashion with just as much success.
Keyed bicycle locks typically come with at least two keys, allowing you to have a spare in case you lose one. The majority of manufacturers of bike locks offer key replacement services in the event that you misplace your keys.
The vast majority of U-locks, as well as some cable and chain locks, come equipped with keyed locking mechanisms.
Combination locks are convenient in that you do not need to remember to bring a key with you or worry about losing keys; but, you do need to memorize a four-digit code in order to open the lock.
A combination lock is the typical method of security utilized by cable locks.
Learn more: How to Bike Ride as a Family