The best bicycle chain locks

Feb 25, 2026

If you're securing your bike in a high-risk area — or leaving it unattended for any length of time — a chain lock or D-lock is essential.

But with so many different link diameters, lengths, materials and types of lock available, it’s difficult to know what represents good value and what simply won’t stand up to attack.

Not all chains are created equal.

A quality security chain will deter opportunist thieves — the type who would rather cut through a cable lock in seconds and move on. A poor-quality chain, however, can be defeated just as quickly with portable bolt croppers.

In this guide, we’ll cover:

How much you realistically need to spend
The chain thickness that actually matters
Why length is critical
Why the padlock is just as important as the chain
How to use your chain correctly to maximise protection

What Do You Need to Spend?

This question is difficult, if not impossible, to answer. Your security chain’s cost changes according to:

It’s length
The link diameter
The quality of metal used
Whether the links are round or square
Whether the metal has been hardened
Whether it comes supplied with a padlock

I know for a fact that I would never purchase a chain that cost less than £50.

Why I'd avoid a sub-£50 chain

Okay, so you might not want to spend fifty pounds on a chain, but consider these points

What will you have to pay on your excess if you claim on your insurance?
How would you get from A to B if your bicycle was stolen and what would that cost?
What about the higher insurance costs if you do claim?
What about the time you spent filing insurance claims, reporting the crime, and talking to an insurance company representative on the phone?

According to some guides, you should spend between 10% and 15% of the value of your bike on security. I get where these guides are coming from, but I don’t believe this is really helpful.

What I advise is that, if you can afford it, you should spend a minimum of £100 on physical security. More if you can afford it.

You could buy a decent chain lock and D-lock for that money. Although it may seem like a lot, the money will be well used. If you are on a tight budget, go for a shorter but thicker chain.

Ultimately what you spend is down to you, but I want you to think twice about buying that sub £30 chain or D-lock.

A little extra spend makes ALL the difference.

Chain Buying: Key Factors to Consider

Chain Thickness

The thickness of your chain determines whether or not specialist tools are required. The thicker the chain, the larger, nosier and less subtle the tools are that are required to use it.

For example a 6mm chain can easily be snipped by bolt-cutters that can be carried in a small rucksack. Anything over 11mm is going to require larger croppers, probably 36 inches and significantly more time.

A well-locked bicycle with an 11mm chain will be VERY hard for a thief to bolt-crop. Anything over 13mm will pretty much rule out the cropping method and require an angle grinder. This eliminates the opportunist bike thieves.

8mm and thinner

This diameter chain, in my opinion, is not worth it. Many of the budget brands that are offered on eBay or at stores like Halfords or Screwfix are 8mm thick. Your local bicycle shop may well be full of them.

You could say that since you can’t get past them without serious tools, and that some get a Sold Secure Bronze rating then they are OK to use.

However, an 8mm chain may be cut with even a set of 12′′ bolt cutters (most of these bike-stealing parasites carry 24" croppers at a minimum).

Due to consumer pressure, cheaper chains are produced and, obviously, purchased by customers who are on a budget or who believe it to be good enough.

Yes, some 8mm chains are rated Sold Secure Silver but I’d rather use a thicker D-lock than an 8mm chain.

10mm

Due to its more appealing price point, 10mm is a common thickness.

A 10mm chain is a fantastic choice if you need portability. Some people carry them around their waist but you can carry one in your rucksack, no problem.

It’s important to note that security chains with a 10mm thickness vary in quality. Some will use case-hardened and chemically treated metals where as others will be made of lightweight metal that should never be sold with security in mind.

Some 10mm chains will scrape in with a Sold Secure rating but the same chains also score a 2 our of 5 in the ART tests, so you can definitely do better.

However, there are numerous companies and non-branded eBay sellers who sell 10mm chains that I would barely trust to lift a bucket of water from a well, let alone protect my bike.

One word of caution: if you’re going to use a 10mm chain, make sure it’s from a reputable manufacturer like Abus, Squire or Kryptonite so you can be sure it’s manufactured of high-quality materials by businesses that care about their reputation.

11mm-13mm

Chains begin to get serious at this level but they also get heavy and pricier but I think the extra spend is worth it.

For me, the greatest benefit of choosing 11mm or thicker is that you can immediately weed out the majority of the manufacturers of junk chains.

Although Gold-rated Sold Secure bicycle chains start at 10mm, it’s worth noting that the smallest Sold Secure Gold motorbike chain is 11mm thick. I really don’t think thieves that steal bicycles or motorbikes carry different tools, so I'd look at 11mm is a minimum thickness.

The more reputable brands begin at about 11mm and run all the way up to a huge 22mm (more on that, below).

If I was securing my bike at the same spot regularly, the thinnest chain I’d use is an 13mm chain. Yes, they are weighty but not obscene. You can get them with a noose ring on one end, meaning you can carry a shorter length chain. Pair it with a high quality D-lock and you've got a great combination.

It's almost impossible to bolt-crop a 13mm chain and this is where I'd start if I was securing a bicycle or motorcycle outside for any length of time.

The links on chains of this thickness can differ depending on whether they are square or rounded. Round links are far more difficult for angle grinders and bolt croppers to grasp.

You should choose rounded links over square links.

16mm

There are chains between 13 and 16mm thick but anything above 16mm isn’t bolt-croppable, so if you’re going for a chain to eliminate this common tool, 16mm is where it’s at.

These are not portable, well, not unless you’ve eaten your spinach. You can get 16mm chains in shorter lengths but they're still hefty things to carry, especially on a bicycle.

A 16mm chain is excellent for home security because it can’t be cut with a bolt cutter by hand and takes some time to defeat with an angle grinder.

16mm chains are generally only produced by companies who care about security and their reputation and not just their profits.

A 16mm chain and a waterproof bicycle cover are effective deterrents for bike thieves if you park your bike outside, say in a communal bike shelter. Most thieves won’t even try and take on a 16mm cain, unless the bike's worth a serious amount of dosh. They’ll just pinch the bike in the rack with the least security.

If you’re parking your bike at home, for example down the side of your house or in a car port, you should consider a ground anchor or wall anchor, which means your bike is tethered to a solid object and can’t simply be carried away. They’re not expensive and are simple to install.

19mm – 22mm

A 19mm chain and larger is carrying on with the same ethos as the 16mm versions: basically they’re chains that will require serious tools, time and commitment from the thieving scumbags.

If you really want the best, a 19mm chain is a fantastic option for home security. However, it’s not that portable. Plus threading the links through your bike is a delicate task – you don’t want to chip your paint work.

You can even get 22mm thick chains but for me these are slightly overkill for most bicycles. The 16 or 19mm are the best ratio of price, performance and usability. The 22mm chain links weigh almost 1kg each and they’re a health hazard if you leave them in the middle of the garage floor!

Chain Length

One of the advantages of a chain over a D-lock is flexibility. You can secure your bike to larger objects such as:

Lamp posts
Railings
Thick racks

However, most chains sold are longer than what a typical cyclist requires to lock their bicycle.

How long should your chain be?

If locking in the same place daily:

Measure the distance needed to loop through frame + wheel + anchor

You’ll likely need no more than 80cm

Chains over 1 metre become cumbersome and heavy (often 3kg+).

Excess chain also creates slack — which makes bolt-cropping easier.

Prioritise thickness over length.

What lock should you use?

A chain is only as strong as its weakest component.

If you use a 12mm thick chain with a £20 padlock, a thief will simply attack the padlock.

When choosing a padlock:

Minimum 10mm shackle thickness
Preferably a closed shackle design
Hardened steel construction

Mini D-lock style padlocks (14mm+ shackles) provide excellent resistance.

Never compromise on the lock.

Chain vs Bolt Croppers

You might see angle grinders attacks on social media - but mainly because the sparks make for compulsive viewing.

Angle grinder attacks are still not that common - they make a lot of noise, create a shower of sparks and are in no way subtle. Bolt croppers are one of the most common theft tools thieves use to steal bicycles, because, quite frankly, bicycle security generally is poor and bicycle thieves don't need angle grinders.

A summary table of security chain thicknesses and their likelihood of being cut with bolt-cutters

Chain link diameter	Can it be bolt-cropped?
8mm and thinner	Yes
9-10mm	Yes. Although some hardened chains will be harder to crop but ultimately most sub 11mm chains are susceptible to bolt-croppers, even shorter ones.
10-12mm	Yes, but it will require the longer sets of bolt croppers (between 36 and 42 inches long), lots of leverage and time.
13-15mm	Highly unlikely. It requires the longest croppers (42 inches long), lots of leverage (i.e. your chain is on the floor) and a good technique, not to mention plenty of time.
16mm and thicker	Not possible to crop by hand

Portable vs Static Use

It’s always worth considering where you’re going to use your chain. If you have to carry it miles to work and back on your bicycle, you’ll be forever cursing me if you buy a 16mm chain (although it will be good at the job it’s designed for!).

If you need to carry your chain, try and stick to 11mm as a minimum thickness and just get as short as possible a chain in order to reduce the weight you have to carry. This is where Noose chains are handy - as you an carry a shorter length.

If possible, couple a good security chain with a quality D-lock (which you can mount on your frame) and you’ll have the ability to lock both wheels and the bike to a solid object.

My recommendation for a chain that you use at home and occasionally carry with you is to get one that’s 11mm thick at a minimum, 13mm is you can.

If you’re never moving your chain much further than a few yards around your home location, then a 16mm is my recommendation. The thicker the chain, the better.

Sold Secure Gold & Diamond Chains

Sold Secure independently tests security products using defined attack tools and time limits.

For bicycles, ratings are:

Bronze
Silver
Gold
Diamond

In high-risk environments, Gold should be your minimum. Diamond offers additional resistance. There is little reason to choose Bronze or Silver when Gold-rated products are typically only marginally more expensive.

Final Thoughts

A bicycle chain lock is one of the most versatile and secure ways to protect your bike — but only if chosen correctly.

Focus on:

Minimum 11mm thick
Keep the length as short as possible to prevent excess weight and slack
High-quality hardened steel
Pair it with a quality closed-shackle padlock or D-lock

Security is about raising the risk required to steal your bike. That means your security should cause a thief to have to use effort, make a noise and be exposed for a period of time.

If a thief thinks the odds are stacked against them, they'll simply move on to look for the next target.

Bicycle Chain Lock FAQ

Is a chain or D lock better?
Neither is universally better. A D-lock is lighter and more rigid; a chain is more flexible and better for larger anchor points. For high-risk areas, using both offers the best protection and if you don't lock your bicycle to anything, then neither are that useful.

Is there a bike lock that cannot be cut?
No. All bike locks can be defeated with enough time and the right tools. The goal is to delay and deter, not make theft impossible.

Which cycle lock is best?
A Sold Secure Gold or Diamond–rated lock from a reputable brand is best. For high-risk areas, a 12–16mm hardened chain or a high-quality D-lock is recommended.

What's the best way to lock a bicycle with a chain?
Loop the chain tightly through the frame (and ideally the rear wheel) around a fixed, immovable object. Keep the chain off the ground and minimise slack.

Which type of bike lock is safest?
Heavy-duty hardened steel chains (12mm+) and high-security D-locks offer the strongest resistance. Thicker chains (16mm+) provide the highest bolt-cutter resistance but they are not portable.

What is the hardest bike lock to break?
A 16mm hardened security chain or a top-tier Diamond-rated D-lock is among the hardest to defeat with manual tools.

Will bolt cutters cut through a bike lock?
They can cut cable locks and thin chains easily. Chains that are 10mm thick and under are vulnerable. Most 16mm+ hardened chains are impossible to crop by hand-operated bolt cutters.

How do thieves break bike locks?
Most commonly with bolt cutters and portable angle grinders. Poor locking technique and excess slack can make attacks easier.

What grade chain cannot be cut with bolt cutters?
In practical terms, 16mm or thicker hardened security chains are considered resistant to manual bolt cutters.