What Are Bike Locks Made Of?

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If you are looking for the best bike protection you can get, you may be wondering what bike locks are made of, and how the different materials work together to prevent bike theft.

The truth is, there are a wide range of different bike locks, and they are all made of different materials.

Let’s take a closer look.

The U Lock

A U lock (also called a D lock – both names coming from the distinctive shape) has an open U that is used to encircle a bike frame, wheel, and a third object, like a bike rack, to secure your bike.

You then lock a horizontal crossbar into place and securely attach the frame and wheel to the object.

What are U Locks Made from?

The best U locks are made from hardened steel.

Hardened steel is a type of carbon steel that has been specially heat treated.

This treatment gives the steel its unique properties of durability and strength.

Ideal for a U lock. The thickness of the diameter of the lock determines how strong it is and, similarly, influences how heavy it is.

Good Points

A U lock is the best kind of lock for securing a bike, provided the diameter of the steel exceeds 13 mm.

Below 13 mm, you can simply use bolt cutters to get through a U lock. Above 13mm a U lock will resist attempts to at cutting and being pried open using leverage.

As a result they are a very good method for securing a bike.

Any Vulnerabilities?

No bike lock can resist a thief with an angle grinder and the time to use it. However, angle grinders can be noisy and, as a result, will draw attention.

They wouldn’t be the preferred method of stealing a bike.

If there is a lot of space inside the U lock they can be vulnerable to being pried open with a jack.

Plus a U lock is only as good as the locking mechanism itself.

If the lock uses a pin tumbler then you can pretty easily defeat those lock types.

Minimize The Size

While U locks provide you the best protection for a bike, having a large diameter lock made of hardened steel can add up to a lot of extra weight for you to carry around.

That’s a weight that you will have to carry.

Use the smallest U lock you can to reduce weight and, as a result, leave as little space for a jack as possible.

The Chain Lock

A chain lock is a length of chain, often covered by a plastic sleeve, which you can then secure with a lock.

Effectively using a chain lock means wrapping the chain around the bike frame, one or both wheels, depending on the length of the chain, and a third object like a bike rack. You then close and secure the chain with a lock.

In this case the old saying is true — a chain is only as strong as its weakest link and that is certainly true here.

What are chain locks made from?

The best chains for bike security are made of a hardened steel alloy and have hexagonal, or square-shaped, links.

These are more difficult to cut with hand tools.

As with U-bolts, the thickness of the links determines whether they can be cut with bolt cutters.

However, because chains are made of links of metal looped together they will naturally take twice as long to cut through.

Good Points

Chain locks are very flexible so they give you more options for locking your bike.

They can be used, for example, to lock your bike to a large lamp post or another large and awkward object.

U locks, on the other hand, can’t do this because of their rigidity.

This flexibility makes them virtually immune to jack attacks.

Links that are 13-15 mm in diameter require very large bolt cutters.

Above 16mm and they are virtually impossible to cut through with normal tools.


Above a certain diameter, the weakest point of a chain lock is usually the lock itself.

Many locks are easily picked or broken, particularly if they are near the ground where a thief has the leverage to smash or
cut at the lock.

The best way to secure a chain lock is with a mini U lock designed to act as a padlock.

Any Downsides?

Chains made of hardened steel alloys are the heaviest way to lock a bike but can be cumbersome to carry when not in use.

To reduce weight use the shortest length of chain you can get away with which will also help keep it off the ground.

Many people opt to use other locks during daily bike riding and leave their chain at home for extra security overnight. That way they don’t have to carry the chain.

Type of Bike Lock: Cable Lock

Cable locks consist of a long, flexible cable, often with an integrated lock (although you can buy a cable and lock separately).

Cable locks operate similarly to chain locks with the cable being threaded through one or both wheels, wrapped around the frame, and locked to a third object.

Like chain locks, their flexibility allows you to lock your bike in a wider range of ways to a wider range of objects.

What’s a cable lock made from?

Most cable locks are made from twisted or braided steel wire in a jacket of PVC or other plastic material.

The exterior vinyl coating prevents the steel from corrosion or damage while also preventing the cable from scratching or abrading the bike or other surfaces.

Some higher-security cable locks have an overlapping steel jacket between the wire cable and the vinyl coating.

Good Points

People like cable locks for their light weight and flexibility but they offer little serious protection from bike theft.

They would primarily be used as a visual deterrent for securing your accessories.

They are easily defeated, unfortunately.


All cable locks are highly vulnerable to bolt cutters. Poor quality cable looks have a weak attachment between the lock and the cable, often held together with simple epoxy that becomes brittle over time and separates.

Poor quality combination locks have a visible gap between the discs that allow someone to crack the combination visually.

Any Downsides?

Everyone thinks they have a good cable lock until you come back to your bike and find it’s been cut and your precious bike is missing.


For the ultimate in bike security, experts recommend combining two different bike locks that work in two different ways.

This way, thieves need different tools or skill sets to defeat both.

This costs a thief extra time and money for tools that they may consider too much hassle.

However, bike owners also have to determine how much weight, cost, and complexity they are willing to manage to protect their bikes.

There is no perfect bike security solution (yet) but knowing what your locks are made of will help you make the right choice for you and your bike.