Learn How to Break a U Lock in 3 Steps

When you first bought your U-lock, the very least of your concerns was to ever have to break it yourself. Understandably, you bought a top-of-the-line security device that would have been marketed as ‘indestructible.’ Now, you can’t find your spare key and the bike needs to be moved and used – what do you do? You learn how to break a U lock.

What is a U lock? A U-shaped lock is designed to lock in between the bicycle frame and wheel. Thereby preventing anyone from moving the bike. In this case, it’s preventing you from moving it too. 

Before we get into learning how to do it, here are a few things you might want to consider:

  • Try finding the spare key
  • Contact the manufacturer
  • Go to the nearest police station

If none of these situations help, it’s time to get down to searching how to break a U lock with a hammer.

How to Break a Bike U Lock Easily

The three most common ways of breaking U lock include:

  • Using a hammer and an air spray
  • Jimmy the lock open with a ball-point pen
  • How to break a lock easily with an angle grinder

The main difference between a U lock and a chain lock is the shape and rigidity of it. A U lock is designed to be practically indestructible and has therefore been used for decades.

A chain lock, on the other hand, is slightly more flexible and therefore can be easily manipulated by anyone looking to steal your bike. In this case, it’s always recommended to remember and note down your bike serial number.

In this case, no one’s stealing your bicycle. You’ve lost the keys or the keys are jammed into the lock and you need a way to move your bike.

I mean, it’s either learning how to break it or how to cut a U lock

1. Use a Hammer and Air Spray

Your first instinct was to grab a hammer and smash it open. While it might be tempting to destroy a U lock that way, it won’t work.

Hammers and excess forces are two things U locks are manufactured to be resistant to. In this case, a hammer will only work if the lock is weakened by an air spray beforehand. 

Why air spray? An air spray is a canister of compressed air at -13 degrees containing chemicals, such as difluoroethane – the implicating chemical in reducing temperatures below freezing point.

At -13, the U lock will be weakened and easier to smash open with a hammer.

  • Find the right air spray and position it a few inches away from the U lock while you spray it inside of the keyhole.
  • You’ll notice the keyhole and the area surrounding it gradually turning white. This is indicative of the U lock becoming brittle. The brittleness is what we’re aiming to target when hammering away at the U lock as shown on how to break a U lock guides.
  • After a few sprays and once it’s white enough, use a hammer to smash through the keyhole of the U lock. Be careful not to move your fingers around too much. 

One important consideration is that the U lock shouldn’t be attached to the bike frame.

2. Jimmy a U Lock with a Ball-Point Pen

Perhaps the simplest yet most effective way to unlock a U lock is by jimmying it open with a regular ball-point pen.

People have been learning how to get a U lock off a bike with complicated machinery ordered online when the easiest and most effective ‘machinery’ is in your drawer.

  • Look for a pen with a cap that ‘pops’ off instead of one than screws off. These are the simplest and cheapest kinds of ball-point pens you can buy. Which is why you’ll probably find one, two, or a couple more at home. 
  • Take the cap with your fingernails to expose the open tube. Measure the tube to make sure it’s almost of equal diameter as would be the keyhole of the U lock.
  • Next, insert the open tube inside the keyhole of the U lock. Make sure it fits exactly and comfortably into the lock. If it doesn’t fit or fits with some resistance, find another stick pen.
  • Hold the U lock with one hand and insert the tube inside of the keyhole with the other. Jimmy the tube inside of the keyhole by pushing it in and twisting it along the way. Don’t use excessive force for how to break a U lock because the tube might break inside of the keyhole. You don’t want more problems than you began with.
  • In anywhere between a few seconds up to a couple of minutes, the U lock will unlock open if you keep twisting it.

3. Use an Angle Grinder to Cut Through the U Lock

Angle grinders are powerful tools meant to cut away and through metal. A U lock has a metal component where you insert the key to open it.

Therefore, an angle grinder might just be the easiest (albeit the most expensive) way to learn how to break a U lock.

Understandably, a few safety precautions must be followed when using a power tool around your bicycle wheels:

  • Use work gloves and goggles
  • Use the right-sized disc for the angle grinder
  • Clamp the U lock onto a surface to prevent it from moving

Angle the grinder at 15-30 degrees holding it a few inches away from the U lock. Bring the blade along with one of the sides of the lock.

You’ll probably see sparks flying, but that’s where the goggles came into play. Slowly cut through one of the U lock’s sides for about 15 seconds until the lock chips away.

Make another cut at the other side of the lock and voila!


Breaking a U lock might seem like an impossible feat – probably because they aren’t meant to be broken.

What now? Live with a chained-up bike and marvel at it while it rusts away?

How about using any one of the three steps mentioned here to learn how to open a U lock? The latter sounds better.

Do you have any question about this process? Please let us know in the comments section below!

Shailen Vandeyar

A proud Indian origin Kiwi who loves to plant trees and play with my pet bunny when not out cycling through the best routes, reviewing the latest gear, and sharing tips on everything biking.

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