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Bicycle locks explained

Updated: 14/10/2020.

This post explains bicycle lock types, construction, and how to choose a good one for locking a bicycle. For instructions on “locking techniques”, i.e. how to properly lock a bicycle, read this post: Locking a bicycle.

Contents:
1. What makes a good bicycle lock?
…1.1. Lock cylinder
…1.2. Locking mechanism
…1.3. Lock body
2. Padlocks – size and design
3. Bicycle locks – types
…3.1. Chain
…3.2. U-lock
…3.3. Cable
…3.4. Folding lock
4. Two is better than one?
5. Final notes
…5.1. But I saw a YouTube video?!
6. Bicycle lock recommendations


1. What makes a good bicycle lock?

Chain is as strong as its weakest link. That is why it is important that both the chain and the lock itself be hard to break, or pick.

Some thieves like to cut locks, some break them, while others try to lockpick the lock cylinder, using special tools (this takes some skill and experience, depending on cylinder quality). It is impossible to tell what “kind” of thief will try to steal a bicycle, nor what tools they will bring. That is why it is risky, for example, choosing a lock that is tough to cut, or break, but has a weak cylinder, easily picked.

This is something people often do. Even when they pay a bit more to get a lock that is sturdier, they don’t go all the way (usually dobule the price of the weaker locks) to get a good cylinder as  well. Or vice-versa, getting a top clas cylinder and key, but paired with a relatively thin (less expensive) chain.

Lock consists of the following three parts and they should all be of good quality:

  • Cyclinder – part where the key comes in.
  • Locking mechanism – part that connects and disconnects (the chain, or cable, or steel rod)  when the key is turned.
  • Lock body – casing protecting cylinder with the locking mechanism, and the chain/wire/steel-rod that locks.


1.1. Lock cylinder

Lock cylinder should be such that it is hard to pick. That means a good key and well protected mechanism. Combination cylinders are generally (not all) less secure, those with a key are usually better. A type of key tells a lot about the cylinder quality.

Regular key. It can be with teeth on both sides. These locks are picked within minutes.
Regular key. It can be with teeth on both sides. These locks are picked within minutes.
Key with holes engraved. A bit safer and better lock.
Key with holes engraved. A bit safer and better lock.
The Abloy lock and key. Almost impossible to pick. The teeth of the key start deep, after a few cm, because the lock is put deep inside the case - to prevent brute force attacks.
The Abloy lock and key. Almost impossible to pick. The teeth of the key start deep, after a few cm, because the lock is put deep inside the case – to prevent brute force attacks.

The last key (above, rightmost), for Abloy rotating disc cylinder, is one of the hardest to pick. If the lock mechanism is put deep inside the casing (like in the picture above), it makes drilling also a problem (anti drill plates are usually installed), which leaves the thieves to look for an alternative method: cutting, breaking, but the cylinder itself is usually a safe link in this situation.


1.2. Locking mechanism

Good locking mechanism should prevent opening the lock by force, while it is locked (enclosed).

Locking mechanism - should hold the steel rod in place when locked, preventing it from being pulled out by brute force.
Locking mechanism – should hold the steel rod in place when locked, preventing it from being pulled out by brute force.
Steel rod pulled out, the lock is open. Good locking mechanism makes this very hardly achieved without unlocking the cylinder first.


1.3. Lock body

Lock body is consists of a protective casing with cylinder and locking mechanism inside, along with a chain, cable, or steel rod(s) that are used for locking. Picture above on the right shows this – rivet connected steel rods that are used for locking and cubical steel case that protects the cylinder and the locking mechanism. Pictures below show the protection of the lock cylinder, from up close:

Lock body protects the cylinder - see how deep a key must enter in order to reach the cylinder mechanism.
Lock body protects the cylinder – see how deep a key must enter in order to reach the cylinder mechanism.
Keyhole protection. Behind the cone plates shown in the picture (protection from dirt/water), there are usually anti-drill plates, before the lock mechanism is reached.
Keyhole protection. Behind the cone plates shown in the picture (protection from dirt/water), there are usually anti-drill plates, before the lock mechanism is reached.


2. Padlocks – size and design

Things explained in chapter 1. go for all the lock types. In addition to that, when choosing a padlock, it should fit snugly around the chain, or cable it connects. For a thinner chain it is better to have a smaller padlock that fits tight, than a large one that leaves a lot of room to insert a craw bar and use leverage to break it open.

Lock that is big, thick, but too loosely fitting.
Lock that is big, thick, but too loosely fitting.
A somewhat smaller lock, that fits snugly. No room to insert a craw bar. :)
A somewhat smaller lock, that fits snugly. No room to insert a craw bar. 🙂


3. Bicycle locks – types

After explaining important stuff about locks and padlocks, it is time to explain bicycle locks. Bike locks are usually made and sold as integrated units combining a chain and a padlock, or a steel rod/cable and a locking mechanism with a cyclinder. There are four basic bicycle lock types:

  1. Chain (and a padlock)
  2. U-lock
  3. Cable (with or without it’s own padlock)
  4. Folding lock

All the lock types are good. If one carries two locks, it is a good idea to combine a cable with one of the other 3 types. This because it takes different kind of tools for those locks: cables are usually cut, while the others are sawn, or broken (or cut if they are too thin, later on that).

Whichever type one chooses, it is important to make sure the lock cylinder and padlock (if the lock type has one) design are good – like explained in previous chapters.

Also, one should never choose a lock that is not heavy. Steel is heavy. If a lock is light, it doesn’t have (thick) enough steel. It is as simple as that. A good lock can easily weigh over 2 kilograms.

Steel hardness is another important factor. It is measured in Rockwell (HRC). Optimal hardness is 65 to 70 HRC. Good manufacturers give that information, while the less good don’t even know it.

Here is explanation of lock types with strong and weak points:


3.1. Chain

Chain with a padlock
Chain with a padlock

Chain should be of hardened steel, such that the core is hardened as well. It should be at least 10 (preferably 12 mm thick). Hexagonal profile (so that bolt cutters press on a wider area, creating less force per mm).

Locking mechanism and padlock should be as explained in chapters about cylinders and padlocks.

Advantages: Second most flexible lock type (behind cable). It allows easy locking around trees, through both frame and a wheel. You take a long chain and put it like you want to.

Disadvantages: weight. A long chain is often quite heavy. 12mm links and 1.5 meters long chain can weigh up to 3 kilograms. Also, it is impractical to carry. Modern bikes have cables and housings all around and long chain needs to be wrapped around some part (top tube, or seat tube usually).


3.2. U-lock

U-lock
U-lock

The same as chains, except here thickness shouldn’t be below 12 mm. Cylinder (key type) should be chosen like it was explained in the chapter about cylinders.

Advantages: lowest weight per level of protection. Moderately easy to carry (it usually comes with an adapter holder for the frame). Even without one it can easily be put on a bike’s rear rack (if it has one).

Disadvantages: THE lowest flexibility. To use a U-lock, one needs to find a post that is not too thick. Even then it can hold frame, along with one wheel if it is close enough.


3.3. Cable

Cable for locking bicycle
Cable for locking bicycle

I’d recommend it as an additional, next to one of the other lock types. The thicker the better. 10 mm is minimum cable thickness. With a good padlock or attached to another lock for keeping it closed.

Advantages: the most flexible, easy to carry.

Flaws: a bit easier to cut than other lock types. Good as a backup lock.


3.4. Folding lock

Folding lock
Folding lock

Made of several steel rods, riveted together. Here dimensions and thickness are not that crucial. If it is made by a renowned manufacturer with a good cylinder, and strong rivets, then it is as safe as a 12 mm thick chain or U-lock. The weakest point of these locks are the joints.

Advantages: among the easiest to carry (comes with a frame mounted holder). More flexible than a U-lock.

Disadvantages: limited flexibility. In spite being better than a U-lock in that department, one often finds themselves wishing for just 10 more centimetres of length, or just a bit of flexibility to the sides.


4. Two is better than one?

The claim is often true, with one big “but”. Two good quality locks are better than one good quality lock. If, however, instead of one decent lock (that is hard to cut, or pry), two cheap, easily cut locks are chosen, that will hardly improve theft protection. It is always a good thing to have at least one really good lock, with an additional lock (for locking wheels for example). Cable is a good choice for a second (back up) lock. Use the better lock to lock the bike’s frame to an immobile object, and the weaker lock to back that up, or to lock the wheels so they too can’t be removed and stolen.


5. Final notes

People are often not prepared to pay more money for a good quality lock. The explanation is usually something like: the bicycle is not expensive, so there’s no use for a lock to cost as half the bicycle’s price. This post author’s advice is: buy a good quality lock once, or you will be buying another (even if it’s cheap) bicycle every month. Good locks cost about 50, or more euros, but last for decades, as well as the bicycles locked with them.

Of course, even a well locked bicycle with a good lock takes just about 20 minutes to hack. If the thief uses a battery powered angle grinder, it is just a few minutes “work”. So no method is 100% safe. However, if a bike is better locked than the other bikes in the street and it doesn’t look more expensive, there is a much greater chance it will wait for you where you had left it. The fact that any lock can be hacked is not a reason to buy a cheap, poor lock, because it’s not all the same for the thieves! The more time and noise a lock takes to beat, the more likely they are to look for an easier prey.

In contrast, cheap bad locks, poorly locked bicycles are taken within a minute or less, with ordinary tools every small thief has, or even without any tools.

I’ll add a short story here – to emphasize the importance of having better protection:
Two friends are preparing to go for a walk in a forrest. One of them puts on some running shoes. His friend asks:
“Why are you putting on the running shoes?”
– Oh, that – in case we encounter a lion.
“What – you think you can outrun a lion?”
– No, I would just need to outrun you.

So, unless someone decides to target your particular bike for some reason, as long as it looks cheaper and is better locked than the others, it’s quite reasonably safe.


5.1. But I saw a YouTube video?!

As I have tried to explain in this post and in chapter 5, 100% secure system is unusable – by definition. The point is to make a bicycle better protected than the other bicycles. Yet, every now and then, I hear comments and am shown (usually YouTube) videos, where people break all kinds of locks, including the good quality ones.

Bad locks are cut within seconds using small cable cutters, or picked within seconds using improvised tools. That is true. But here I’ll discuss the videos where good quality locks are “broken”:

  • For a lock-picking example, I’ll use the video made by LockPickingLawyer with Abus Granit X-Plus U-lock. Someone saw the video and commented how that lock is easily picked. Well, the video’s author is an experienced expert in this field, with all the proper lock-picking tools. As he himself says at the end of the video: “… I do think it has enough pick resistance for securing a bike in the street.” In other words: I know of only two people who have the knowledge and the tools to pick these kinds of locks (not saying there aren’t more, but when I was doing research for writing this post, I couldn’t find them). To them it is not profitable to do crime, especially not bicycle thefts.
  • Using bolt cutters videos: if a lock is a good quality one, bolt cutters used need to be of high quality, with very long handles for leverage – such that don’t easily fit under a jacket, or in a backpack of an average bicycle thief. Also, ground is often used as a leverage for one handle of the cutters, so the whole weight is put into the cutting. My post on how to lock a bicycle explains why locks should be placed away from the ground whenever possible.
  • Battery (cordless) angle grinder example: powerful tool, will cut almost anything rather quickly. See this video of using a cordless grinder on an Abus chain. The chain is held tightly in a vice. All the protective gear is used. See how much noise and sparks this produces – and it’s still not just a 5-10 second job. Not even with the expensive and good quality cordless angle grinder. Imagine having no vice, so that the other hand needs to be used to hold the chain/lock in place. Besides, time goes slowly when stealing, watching if anyone will come, so thieves are very likely to choose easier targets, even with tools like these.
  • Good quality hand saw: 20 to 30 minute of hacking gets through most chains. Poor ones are cut in a minute or two. Thieves don’t like hard work and prefer easy prey.

So it’s no secret that even the best, most expensive bicycle lock can be broken. It’s just a matter of how much time, knowledge and tools are needed to do it. That’s why it’s not irrelevant whether you use a good quality lock, or a poor quality one.


6. Bicycle lock recommendations

Pictures below are my recommendations for good quality, safe bicycle locks. If you’ve carefully read the previous chapters, you’ll probably understand why I’m not recommending anything cheaper. Manufacturers won’t sell good locks, with good (confirmed) reputation, cheaply – when they can sell them for more. Cheap locks are usually, from my experience, either of poor quality, or with no confirmed good reputation. When it comes to things like safety of a locked bicycle, I’m not willing to take risks, even less to suggest to others to take a risk, just because a lock seems like a good one to me, without testing it first. The moment I find a cheap lock that is not easy to open, I’ll be the first to buy it, try it and recommend it here on my website.

Clicking on an image below will take you to Amazon.com online shopping (as an Amazon Associate I earn from qualifying purchases), or you can buy them locally.

All the listed locks are made by Abus. Simply – for those I could get info on HRC hardness, locking mechanism, and I’ve had very good 1st hand experiences (with the listed, not all the Abus lock models are recommended!).

GRANIT CityChain XPlus™ 1060/110. Chain with 10 mm thick links of hexagonal diameter, 110 cm long. Comes with a good quality lock.
Abus GRANIT CityChain XPlus™ 1060/110. Chain with 10 mm thick links of hexagonal diameter, 110 cm long. Comes with a good quality lock.
Abus GRANIT XPlus U-lock, with a 13 mm thick shackle, good cylinder and locking mechanism.
Abus GRANIT XPlus U-lock, with a 13 mm thick shackle, good cylinder and locking mechanism.
Abus BORDO GRANIT XPlus™ 6500/85, folding lock of top quality.
Abus BORDO GRANIT XPlus™ 6500/85, folding lock of top quality.
Abus Steel cable Cobra, 12 mm thick, 120 cm long
Abus Steel cable Cobra, 12 mm thick, 120 cm long.
Good for locking wheels and accessories, but not as a “main lock”.


For people living across the ocean from Germany 🙂 it is probably cheaper to look for Kryptonite locks (Amazon affiliate link) – from what I could see and hear, they have good models, and are a lot cheaper than Abus in the USA, but I haven’t had much 1st hand experience with them. Not saying they are bad, but can’t confirm they are good either.

Related post – How to safely (properly) lock a bicycle:

How to securely lock a bicycle, so it doesn't get stolen
How to securely lock a bicycle, so it doesn’t get stolen
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1 thought on “Bicycle locks explained”

  1. I’m waiting for a u-lock that consists of a hard steel core covered by a reasonably thick aluminum layer and a heavy Kevlar sock.
    I don’t expect it would be heavier than the current all-steel models and would resist grinding (aluminum clogs the grinding wheel) and be impossible to hacksaw without removing the Kevlar and getting through some hard steel.

    Reply

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