D Lock vs Chain Lock – Which Is More Secure?

D locks and chain locks are the two best types of lock for you to secure your bike with. In an ideal world, you’d use a chain lock and a D lock to secure your bike. However, we understand that not everyone has the budget to afford two top of the range bike locks! 

This leaves us with the question: Which is best, D lock vs chain lock?

D lock vs Chain lock is a debate that you can often find on cycling forums. Both lock types offer different features, perform differently and are suited for different styles of usage. 

If you’re looking for something that’s portable and can be used to secure your bike almost anywhere, then you’ll probably want a good quality D lock

If however, you are looking for an ultra-secure lock that will remain in one location (bike shed, garage) your best bet will be investing in a top of the range chain lock.

D lock vs chain lock pros and cons
D locks and chain locks provide a great level of protection for you bike. You'll need to decide which is more suited to your needs.

Table of Contents

 

Below we will break down and compare the differences of D locks and chain locks. We will provide information on the various prices for each lock, how easy they are to use and the level of security they offer. You’ll also find some helpful bicycle security tips and tricks!

The majority of bike locks are relatively lightweight, and most weigh under 2kg. Some, are slightly heavier, but we would still consider these to be useable for everyday lock ups.

 

Milenco Dundrod Bike Chain Lock
14mm bike chain locks such as the Milenco Dundrod are too heavy to carry and are best used as stationary bike locks.

When it comes to chain locks many of the more secure chains weigh in at over 3kg. We would consider these to be static/stationary chain locks that can be used to secure your bike whilst you are at home or at work.

 

D lock vs Chain Lock – Which Is the Most Practical?

 

D Locks – Practicality

D locks, as stated above are normally lightweight and tend to be no longer than 25cm. This means they can easily fit into your rucksack. A good quality D lock will normally come with a mount that will enable you to directly attach your lock to your bike’s frame.

D locks do not feature any links or moving parts. The shackle of a D lock is one solid U shaped piece of metal. Whilst these strong shackles provide good levels of security for your bike, they also limit you with what you are able to secure your bike to.

Best Bike D Lock
With so many different options to choose from it can be difficult picking a lock that suits your needs, Keep reading to find out which works best for you!

 

You might struggle to fit your D lock around an object such as a lamp post because the locking shackle simply isn’t wide enough. This can be an inconvenience if you are in a rush, or if you don’t have knowledge of designated bike parks in the area you’re in. 

There are several top-of-the-range D locks that have earned the Gold Sold Secure rating, that have super small shackles. In some situations, a smaller shackle isn’t ideal, on the other hand, they do provide improved defence against hydraulic and twist attacks.

 

Portable Chains – Practicality

Most Portable chains have a decent length to them, which allows you to explore a number of different locking techniques. The links of a portable bike chain mean that it is easier to use whilst securing your bike to larger objects. Most portable chain locks can secure your bike to lampposts, whilst a D lock may struggle in this scenario.

A good quality portable chain will almost always be heavier than a D lock. Whilst a chain lock will offer more locking options than a D lock, realistically even portable chain locks aren’t very portable.

The Hiplok Lite Wearable - This chain lock can be worn like a belt and is super convenient for use on the go!

 

It can be hard work transporting a chain lock around, and you may have guessed that they don’t come with a carry mount like the majority of D locks. Instead, you are left with the option of coiling the chain lock around your bike’s frame or stowing it away in your rucksack. 

As chain locks (even portable ones) tend to be heavy, securing these directly to your bike whilst riding can actually damage your bike, so we wouldn’t advise this.

Damaged Bike Frame the best bike chain lock

 

Some chain locks are able to be worn by the user. Many portable locks can be worn around the waist or over the shoulder, which makes them easily accessible, but still not majorly comfy.

If you have an expensive bike, that you do not want to damage, you may have to stow your portable chain lock away in your rucksack. This can be uncomfortable but is definitely one of the most effective ways of transporting a portable chain lock.

 

Stationary Chains – Practicality

When it comes to stationary chains, their massive weight is not an issue, because there’s no need to carry them around. Normally stationary chains will also be longer, which gives you more locking space to work with. 

This also gives you the possibility of securing two or more bikes.

The video below shows some of the Pragmasis Protector range. These are the biggest and strongest bike chain locks that are available to date. Since the video has been made they have gone on to release even bigger chain locks!

 

Chain locks work better with ground anchors than D locks do. This is thanks to their greater length and size. A larger locking area can be a good advantage when securing your bike at home, as you’ll be able to secure more than one bike at a time.

 

D Lock vs Chain Lock – Practicality Summary

D locks in many scenarios will be more practical than a chain lock. A good quality D lock will have a Gold Sold Secure rating, and these can be easily stowed away in a rucksack. Whereas a chain lock that offers the same security rating is likely to be substantially heavier. 

Regardless of the extra locking options that you get with a chain lock, it’s hard to compete with the sleek, compact shape of a D lock. 

 

D Lock vs Chain Lock – Which Offers the Best Security?

Both D locks and chain locks have weaknesses that are specific to each type of lock. However, there is one very real threat that affects them both….. Bolt cutters.

For years and years, bolt cutters have been a bike thief’s best friend. Some bolt cutters are tiny and can easily be concealed in a pocket or rucksack, whilst some are hefty and can be up to a metre long! The bigger the bolt cutters, the more powerful they are due to the increased leverage. This means many locks are vulnerable to larger bolt cutters.


A pair of 24" bolt cutters

As bolt cutters are a common weapon of choice for thieves (particularly the 36″ cutters) we need to know how we can combat them. The best thing you can do to stop a thief stealing your bike is to purchase the thickest lock possible. The thicker the lock, the harder it is to cut!

The video below shows just how tough it is to cut the Pragmasis 16mm chain. Bear in mind, this test is being carried out in optimal conditions. It would be 10x more difficult to attempt this on outside on the street!

 

If you want to completely prevent thieves stealing your bike with hand-powered bolt cutters, you should only consider locks that are 16mm (or more) thick. A top-quality 16mm bike lock made with hardened steel can’t be defeated by hand-powered bolt cutters, simply because it’s too thick!

The Kryptonite New York Fahgettaboudit Mini D lock (18mm thick) and the Kryptonite New York Legend chain lock (16mm thick) both have chunky shackles/links. Thieves would not be able to crop either of these with hand tools which is just what we want!

 

Kryptonite Fahgettaboudit Mini
  • Weight: 4.55 lbs (2.06 kgs)
  • Dimensions: 3.25” x 6” 
    (8.3cm x 15.3cm)

 

The thicker the shackle/link the heavier the lock. The Fahgettaboudit weighs in at 2.06kg making it one of the heavier D locks on the market but offers unrivalled protection. The New York Legend chain also weighs in at 4.31kgs.

One of the other things you can do to prevent your lock from being cropped is to learn how to properly secure your bike. Keep your lock off the ground, fill the locking area and make sure that you secure as many components as possible. 

The only thing that’s out of your control is how skilled the thief is that’s trying to nick your ride!

 

D Locks – Security 

D locks have several weaknesses that chain locks aren’t affected by. For example, a poorly secured D lock would be vulnerable to hydraulic attacks. A hydraulic attack is where a car jack is inserted into the D lock’s shackle, it is then jacked up until the lock pops open. 

The image below shows a D Lock’s shackle that has been subjected to a twist attack. I found this whilst out cycling and thought it would be a good example of why you should avoid using flimsy, thin D locks. Someone obviously learnt this the hard way.

A D lock's shackle that has been broken with a twist attack

No matter the thickness of the D lock’s shackle, if the pressure is great enough, the lock will most likely snap open.

Twist attacks are where an object such as a crowbar (or even a large piece of wood) is inserted into the middle of the shackle. From here the crowbar is twisted until the locking mechanism is under too much pressure and pops open. See the video below for a good demonstration.

 

The simple way to avoid thieves utilising these methods is to completely fill the shackle of your D lock. The video shows an empty bike lock being broken open. If the lock’s shackle was securing a bike there would be considerably less space for the pry bar to be inserted and manoeuvred inside the shackle. 

I easily filled the shackle of my Fahgettaboudit Mini, which eliminates the opportunity of twist & hydraulic attacks.


How to lock a bike kryptonite fahgettaboudit

Both D locks and chain locks are susceptible to attacks carried out with angle grinders. However, due to the lack of moving parts/links D locks are easier to cut through with an angle grinder.

Sold Secure, the lock security testing company have reviewed a wide range of D locks on the market. Their tests have shown that many D locks meet the security levels needed to earn the Gold Sold Secure rating. When choosing a D lock look out for the Sold Secure Badge shown below.

The Sold Secure Gold rating is the highest rating a bicycle lock can earn. This shows us that the best D locks are suitable for securing your bike in ‘high risk areas’.

 

 

Portable Chains – Security

With their extra length, it can be hard to keep both portable and stationary chains off the ground. But make sure you do your best! An interesting method used to defeat chain locks is using cold compressed air or liquid nitrogen. 

If metal has it’s temperature drastically lowered, it can be shattered with a powerful blow from a hammer. This method requires time for the temperature of the metal to be lowered so that it becomes brittle. 

The freezing method is less favoured by thieves as more tooling and specialist equipment is required.  

The end of this video below shows a padlock being submerged in liquid nitrogen in laboratory conditions. The metal padlock is then struck twice with a hammer before being completely broken. It’s not 100% clear if this is due to the liquid nitrogen, but it’s widely known that metal exposed to sub-zero temperatures becomes more brittle.    

 

This risk can be reduced by keeping your chain off of the ground and leaving as little slack as possible.

The main issue that portable chains face is the size of their links. To be considered portable we would say that chain locks need to weigh no more than 3kg. 3kg is a lot of extra weight to carry around, and this might be pushing it for some people. 

This ultimately limits portable chain locks to 12mm links or smaller as any larger links would be too heavy to carry.


Bicycle chains of different sizes Sold Secure Gold

As explained previously, the thicker the shackle or links, the higher the security. This means portable chains won’t provide the greatest levels of security for your bike, but they make up for it in other areas.

The shortest 12mm chain locks that we could find was the Kryptonite New York Chain 1210. This weighed in at over 3.9kgs making it nearly twice the weight of the most secure D lock available! Even Kryptonite’s 9mm Kryptolok Series 2 995 chain weighs in at 2.5kgs. This is still almost 500g heavier than the top range of D locks

 

Stationary Chains – Security

Weight is much less of an issue when it comes to stationary chains. As they do not have to be lugged around, you should aim for the thickest links possible. 16mm chain links are bolt cutter proof. 

As stated above, the moving links of a chain make it much harder to defeat, even with the use of power tools. Their thicker links and flexible chain, make stationary chains the most secure bike lock choice. 

 

D Lock vs Chain Lock – Security Summary

D locks do have several security issues that don’t apply to chain locks and vice versa. However, there are a few simple steps that you can follow to reduce the chances of these issues being a threat. Fill the shackle/chain of your lock as much as you can, and make sure to keep it away from the ground.

Portable chains do not have the same security issues as D locks. You can reduce the chances of theft whilst using a portable chain by keeping it off the ground. However, due to their thinner links, portable bike chains will always be more vulnerable to bolt cutters than a good quality D lock. 

This means that for security, D locks will be more secure than a portable chain.

Workers inspect a ships anchor chain
Some say that size doesn't matter. Wrong. When it comes to cycle security the thicker the links or shackle of the bike lock, the better.

 

If you have access to a chain lock that’s links are a decent size (16mm+) this is your safest and most secure option. The thicker links mean that these stationary chains are not vulnerable to bolt cutters. Their flexible chain also means that stationary locks are harder to attack with power tools. 

We’d still advise keeping your stationary lock off the ground if possible. Even the best D lock can’t provide the same levels of security as the best stationary chain lock. But you cant take the best stationary lock on a bike ride! 

 

D Lock vs Chain Lock – Which is the Cheapest?

When it comes to price, D locks are normally less expensive than chain locks. The best bike chain locks normally will come with a small D lock that acts as a padlock to secure both ends of the chain.

Remember, you get what you pay for. If you buy a cheap unbranded bike lock, you'll be leaving your bike vulnerable!

On top of this, chain locks require a larger amount of metal, especially the bigger ones. This adds to the cost of chain locks, but don’t let that put you off. There are some top quality chain locks that are priced reasonably, but they do tend to be a tad more expensive than your average D lock.

It’s important to remember that if you want the best protection for your bicycle, it will come at a price. Don’t be fooled by cheap cable or combination bike locks. These will not provide any protection for your bike and can be removed with wire cutters in a matter of seconds. 

Kryptonite New York Legend 1515
  • Weight: 14.7lb (6.6kg)
  • Length: 4.9' (150cm)

Police in the UK have advised that cyclists should spend 10-15% of the value of their bike on its security. If your bike is worth £50 you may end up spending more than your bike cost on a good quality bike lock. 

Top-quality bike locks will stop your bike being stolen and will provide you with the peace of mind you need whilst you’re bike is locked up.

 

Summary – D Lock vs Chain Lock

If you’re a cyclist that uses their bike to commute into work daily, then your best bet is a good quality D lock. D locks are more secure than portable chains and often have better sold secure ratings.

Normally D locks cost the same, if not less than portable chains. D locks are highly practical and can easily be stored in a rucksack or through a belt loop. The list of benefits goes on. 

If you want the most secure D Lock, that’s portable, super secure and completely bolt cutter proof, youl’ll want to use the same one as I do. The Kryptonite Fahgettaboudit Mini. 

 

Kryptonite Fahgettaboudit Mini
  • Weight: 4.55 lbs (2.06 kgs)
  • Dimensions: 3.25” x 6” 
    (8.3cm x 15.3cm)

The best D locks also come with mounts that allow you to attach the lock onto your bike’s frame. This is a bonus as it means your bike D lock will be available to hand, for quick and easy locking. 

Because the Kryptonite Fahgettaboudit has a larger shackle than all D locks on the market, it doesn’t come with the standard Kryptonite D lock mount. Instead, the Kryptonite Transit Mount can be purchased separately and will provide a practical way to use this impressive lock on the go. 

 

The Kryptonite Transit Mount is available on Amazon here

Chain locks are bulkier and are likely to damage your bike if you wrap them around it’s frame. Some portable chains, such as the Hiplok Gold can be worn around the waist like a belt, however not all portable chains have this feature.

Whilst D locks are a fantastic choice of bike lock, they aren’t suitable for everyone. Some cyclists will require a larger locking area and may require a lock that can secure more than one bicycle. 

D lock vs folding bike lock, D lock shackle won't fit around lamppost
Due to it's smaller shackle size, the Kryptonite Fahgettaboudit wont fit around large lamppost. It will however, fit around all regular bike stands and smaller posts.

 

Some D locks have small shackles that may not fit around larger objects (lampposts, large bike rails, etc), so a portable chain would be better suited in these scenarios.

The video below shows how easy it is to cut a bike cable lock, even with small wire cutters! Don’t get caught out.

 

If you have invested a large amount of money in your bike, then you should consider using a stationary lock. This may not be suitable if you’re constantly on the move. If you’re always on the move, use a top-quality D lock and a cable extension (two D locks is also a good option!)

A thick, heavy stationary bike lock (14mm+) will also provide great security for your bike. Stationary bike locks give you multiple locking options, including securing more than one bike at a time.

If you’re struggling to decide on which bike lock is best for you, then you can take a look at our bike lock buying guide. By following the simple steps set out, you will find out which bike lock best suits you and your bike.

If you still can’t decide which bike lock you require, have a browse of the strongest bike locks, or the best lightweight bike locks if you’re looking for something a little different!

 

 

Sources:

https://www.kryptonitelock.com/en/locks-landing/product-details-bicycle.html

https://www.soldsecure.com/search/

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2 Responses

  1. General advice suggests thieves tend to target EITHER d-locks or chains so securing your bike with both is the best way to go in high risk areas. With that said adding a solid silver rated lightweight 8 or 9 mm portable chain can bring additional security when locking bike in high risk areas. It’s worth purchasing one of either to enable options when judging which to use where too if you are securing with just a single locking device.

    1. You’re definitely not wrong!

      If you have the budget to afford two bike locks, using a chain lock alongside a D lock is a great idea.

      The more metal you put in the way of your bike, the better!

      James

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About Me
Me and My Bike

Hello! My name’s James, I’m an avid cyclist and I’m the lead editor of BikeLockWiki.

I have invested three years into researching & studying bicycle security and I want to share the information that I have gathered with the cycling community.

I do this in the hope that people don’t have to simply become a victim of bike theft to realise and understand the importance of bicycle security. Read More…

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