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How to Break a U Lock? – 3 Simple and Reliable Methods!

Written by Gary Johnson / Fact checked by Henry Speciale

how to break a u lock

U-locks are some of the most reliable and durable bike locks available in the market today. They always come in handy, especially when you are parking a bicycle in crowded and unsafe places. You are certain that your equipment can be protected just by using a u-lock.

However, mistakes happen. There are incidents that you misplaced the key to your bike lock, and there’s no way to unlock it other than to break the lock. Given its outstanding durability, how to break a u lock? Breaking bike locks can include the hammer and air spray method, ballpoint pen method, and angle grinder method.

Ways to Break a U-lock


1. Hammer and air spray method

Getting a canned air spray – One of the most convenient ways to break a u lock is the air spray method. It is important that you have available air spray with you to execute this process. The chemicals (difluoroethane) inside the air spray weaken the material in the u-lock.

You have to do this process before hammering the lock, so it is easier to smash open. Air spray can be bought at the home improvement stores or even online.

Put the U-lock into the right position – If your lock is not connected to the bike, it is easier to smash the lock to open. You should position the lock correctly to not harm or damage your bicycle. Ensure that the lock is lying flat on the surface because using the hammer.

With the use of the bottled spray, put a considerate amount of chemicals at the keyhole of the U-lock. Make sure you are holding the spray about a foot away from the keyhole. Then, hold the trigger, and spray it to the lock’s keyhole.

Spray continuously – Hold the bottle and spray it for 30 seconds. Spray continuously until you notice that that bar is turning white. It indicates that the chemicals from the air spray are reacting on the U-lock materials. It weakens the material and enable you to hammer it easily.

Start hammering – Now that the spray positively reacted to the lock, you can start hammering against the keyhole. The spray will make the lock brittle, too. Make sure that you keep the fingers away from the area you hammer.

(Pro tip: Keep the lock stable to smash the lock better. Do not panic if you see white powder coming out of the lock. It indicates that the lock surface has been chilled making it more brittle)

Hammer until the lock breaks – The force you put on the hammer will break the lock material. To break a bike lock with a hammer, you have to continuously smash the u-lock until it starts to break open. Pay more attention in hammering the broken area of the lock. This portion is easier to come off, and will gradually weaken from hammering.

Stop when you see that the device is completely separate from the bike. It indicates that you have successfully cut a bike u lock.

2. Ballpoint pen method

Get a basic ballpoint pen – If you do not want to buy a chemical air spray, you can also use an ordinary ballpoint pen. It is one of the most practical and effective ways to break a u-lock device. Ensure that you get a basic ‘stick’ pen that have a ballpoint on the tip. This type of pen is the cheapest you can find in the market.

Remove the cap from the pen – Using your fingernails, pry off the small cap on the end of the pen. Ensure that you leave the pen with an open tube as this is the one you will use to unlock the key.

Insert the tube to the keyhole – You can now insert the tube of the pen inside the keyhole u-lock. Make sure the tube fits the keyhole, too.

If the tube does not fit, find another ballpoint pen and redo the process. After you are satisfied with the ballpen, push and twist it into the keyhole. Keep the lock stable by holding it with your one hand, use the other hand in pushing and twisting the tube.

Put enough force when pushing and twisting. Continue with the motion until the lock opens. Keep twisting until you hear a click indicating that the keyhole is already unlocked.

Check the bar of the u-lock – You can pull the bar of the u-lock to inspect. Apply pressure when pulling the bar. It will automatically pull up if you are successful with the process.

3. Angle grinder method

Safety first

  • This is the most effective way to break a u-lock. It is important that you take precautionary motions when doing this. This include the following:
  • Wear safety gloves to protect your hand, and safety goggles to keep the material or debris from your eyes.
  • Wear tight fitting clothes so the debris won’t penetrate your skin. Ensure that you wear the right gear while using the angle grinder.
  • Use the correct size or disc of the angle grinder. It is also crucial that the grinder is working well and can perform at its optimum speed.
  • If you are breaking a u-lock not attached to anything, it is essential to use a clamp when cutting it with the grinder. It will keep the lock stable and safer for you.
  • If the lock is attached to the bicycle, get the correct position and adjust according to the pressure you put while using the angle griner.

Use the angle grinder – After you are certain that the lock is stable, turn on the angle grinder to start cutting the u-lock. For this step, you must hold the angle grinder with both hands at about 15 to 30 degrees. Make sure you are holding the device a few inches away from the lock.

Cut the u-lock bar – Gradually bring the blade against the side of the u-lock to start the cutting process. You will see sparks fly from the area you are cutting, but this is not worrisome. The sparks fly are just debris indicating that the metal material is being cut through.

Keep the blade at a steady position until it dives deep to the metal material. You will consistently encounter sparks fly, but this is normal.

(Pro tip: It is crucial to be slowly and deliberate when employing the angle grinder. The key here is to keep the blade steady in one portion of the u-lock bar. Do not put too much force or pressure on the grinder. The motor power is enough for the grinder to cut the metal piece)

Make another cut to the bar – This process is for u-locks attached to the bike or door. You have to cut the side opposite the first cut to properly dislodge the u-lock and avoid damaging your bike. Apply the same process you applied on the first cut. Keep the blade steady and prevent putting in too much force. Stop when you see the bar successfully dislodging.

Turn off the grinder – After completing the cut, turn off the angle grinder. Remove the u-lock from the bike and keep the grinder in a safe location. Then, clean the working area to remove the debris from the metal lock.

Also, check this video to find out how to break a U lock in a minute:


U-lock may be the standard for bike locks, but it can be such a hassle if you misplace the key or are unable to unlock it. Good thing, there are ways to unlock a bike lock without a key. The three methods we shared with you are tried and tested. Depending on the availability of tools, you can choose the most practical and convenient process to break the lock.

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