Introduction

No bike lock is impenetrable

The National Bike Registry estimates that 1.5 million bicycles are stolen each year with a vast majority of these thefts not being reported to authorities. In 2004, the Federal Bureau of Investigation (FBI) reported that more than 250,000 bicycles were stolen. Take into account that the average value of a stolen bike is approximately $240, and that equates to more than $60 million in stolen property. As a matter of economics, a bike lock could be a worthy investment. Even though no bike lock is unbreakable, they can be an effective deterrent against theft.

Experts say you shouldn't think twice about investing at least 10 percent of your bike's value in a good lock -- or multiple locks. Reviews indicate that the best bike locks are U-locks or chain locks. U-locks have a thick steel shackle that is attached to a crossbar with a keyed lock. Chain locks have tough links that are typically attached with a small disc lock, requiring a key to open. Both of these types of bicycle locks can effectively secure your bike, but U-locks are usually lighter and more portable than chain locks. Many cyclists use a large chain or U-lock to secure their bicycle to a stationary object, while using smaller U-locks or cables to secure wheels and seatposts. If you live in a high-theft area, you may want to invest in several locks for maximum security.

There are also numerous cable locks on the market, but you won't find many experts who recommend these locks. Cable locks use steel cables attached to a combination dial or keyed padlock. A cable lock is certainly better than no lock, but they can be easily broken in seconds and provide little security in high-theft areas. Still, cable locks can be good secondary locks when used in conjunction with a tougher chain or U-lock.

In general, U-locks are thought to give you the best protection against bike theft, but even these bike locks aren't perfect. You may remember reports of U-locks with cylindrical keyholes -- including pricey locks from Kryptonite -- being picked with ballpoint pens. In 2004, The New York Times reported that several other brand-name bicycle locks and several locks for vending machines, security panels and other devices were also vulnerable to a thief armed with a pen. YouTube hosts numerous videos demonstrating these pen-wielding lock pickers. Even though Kryptonite reacted quickly with upgraded replacements, recalls and new bicycle-lock designs, they still caught a lot of flack.

We found a number of comparative reviews of bike locks, but many of these are outdated and conducted outside the United States. The best American tests come from Wired and Men's Journal, as well as an older article at Slate.com. Wired's attempt to break bike locks with both hand and power tools is the most recent, but the locks tested and reviewed are less common. Men's Journal tests five bike locks using a variety of tools, rating each lock on security and usability. Similarly, Slate.com's Scott Elder tries to break nine bike locks with a crowbar, 30-inch bolt cutters, a hacksaw, three types of blades and "my trusty claw hammer."

We also found good -- but not comparative -- reviews at BikeRadar.com. Contributors to this site test locks for strength and durability, but they don't compare the locks to others on the market. Owner-written reviews are also helpful, especially at Amazon.com. Many bike locks attract at least a dozen reviews on Amazon.com. Other review sites, like Buzzillions.com or TotalBike.com, have a few reviews but are far from comprehensive.