If you own a bicycle, investing in a bike lock is a good idea to protect your bike from theft when you're not using it. There are several types of locks available at sporting goods stores and bike shops. Some use cable or wire to connect to your bike, while others feature combination locks or are composed of thick, U-shaped metal bars. If you forget your combination or lose your bike-lock keys, you'll have to remove your lock so that you can use your bike again.
Try to remember your combination or find your keys before you attempt to cut your lock. This is the easiest way to remove your bike lock, so give yourself plenty of time to think about your combination or look very carefully for extra keys before you give up.
Cut your lock away from your bike. If your lock is made of cable, wire or a chain, use bolt cutters to remove your lock. Have a friend tightly grip your lock with both hands and hold it taut while you cut it. This may take a few tries, but it is the only way to remove a cable, wire or chain lock. Exercise caution when using a bolt cutter and only attempt to use it if you have previous experience with one. Do not attempt to cut the chain by yourself as you will not be able to hold it taut and hold the bolt cutter at the same time.
Use a crowbar to remove a U-lock. Insert the bar in the middle of the U-shape and leverage enough force against the lock to pop the locking mechanism away from the U-shaped bar. This is how professional thieves remove U-locks, even those whose manufacturers claim are resistant to crowbars, from bikes. Use caution in attempting this method to avoid injury.
Call a locksmith or consult a bike-lock professional at a bike shop for help. It's better to pay for a professional to remove your lock if you are unable to do so yourself than to continue to try to remove it yourself and get injured. A locksmith may be able to pick your lock in such a way so as not to render it broken when he's done. This could help you avoid having to purchase a new lock.
Write down your combination and store it and/or an extra key to your lock in a safe place to prevent this from happening again. E-mail your combination to yourself so that you can access it on your smart phone, if you have one, at any time. Some bike-lock manufacturers, such as Kryptonite, offer key-replacement services if you register your lock with them when you purchase it. Take advantage of such services by filling out the appropriate form when your buy your lock.
Exercise extreme caution in attempting to remove your lock to avoid injuring yourself or anyone around you.