Before selecting the appropriate bike lock for your needs, there are a few things you should consider:
Do you live in a high-theft area? Even if you don't live in a region where bicycle thefts are frequent, you may want to opt for a higher level of security. It's generally a good idea to spend more for a higher-quality lock with a correspondingly better warranty from the manufacturer's protection plan.
How do brands rate their locks? Look at the in-house and independent rating systems to get a relative idea of how the manufacturer positions its own products. Kryptonite, for example, rates its products on a 12-point scale, with 12 being the most secure.
What size lock do you need? Consider two U-locks, or a U-lock and a chain lock. Most U-locks will fit around your bike's frame and rear wheel, but your bike seat and front wheel are still easy to access. Consider exchanging your quick-release bike seat post for one that locks and adding a secondary lock to protect the front wheel.
You get what you pay for. There's no way around it: Bike locks can get pricey, especially if you opt for top-of-the-line models from well-known brands. While it may feel unnecessary to spend another $50 to $200 on a bike lock, it's much less expensive than having to potentially buy a new bike. If you purchase a higher-end bicycle, expect to spend at least 10 percent of your bike's value on a lock. Pricier locks tend to perform better in tests, and companies tend to back them up with theft protection warranties that can reduce the pain and cost if your bike is stolen. Many of these warranties require a certain amount of paperwork, but it's worth it in the event that your bike is lifted.