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A Combination Bike Lock: Is it really less secure?

Last Updated on August 20, 2022 16 Comments

A combination bike lock

The short answer is: yes! Locks that you open with a code are generally less secure than locks that require a key. But why is this and does it mean we should avoid combination bike locks altogether?

Well, not necessarily. Let’s look at this in more detail…

So, just to be clear: combination bike locks are the ones with a several dials of numbers that you turn around to make a combined code that opens the mechanism. There are usually 3, 4 or 5 rings so the code is 3, 4 or 5 numbers long.

These locks are popular because you don’t need a key: as long as you can remember the code you can always unlock your bike. And you can also give the code to family or friends so they can share the use of the lock and therefore your bike too!

Just try every combination!

3 number combination bike lock

3 dial locks are very quick and easy to crack

The first problem with these locks is the limited number of combinations. With 3 dials there are just 720 unique codes. So with averagely nimble fingers, which could test one number per second, that’s a maximum of just 12 minutes to test every combination. And of course: the correct code isn’t likely to be the last one a thief tries!

4 number combination bike lock

4 number codes take much longer to crack

However with 4 dials there are 10,000 possible combinations. So the same nimble fingers would take almost 3 hours to test every combination. And in reality, testing one a second for nearly three hours while hunched over a bicycle in the street is just not practical. It would actually take much longer, even if the thief had the patience and nerve to persist.

So while it’s true that combination locks can be opened without any tools at all, by someone without any skill at all (beyond counting), if you’ve got a 4 (or more) dial lock then it’s very unlikely that anyone’s going to defeat your lock in this way.

Unfortunately however, the finite number of codes isn’t the only weakness of combination locks…

Or pick them without any tools!

Cheap combination locks are very easy to decode. The way to do this (and I’m not revealing anything new here), is to create tension by trying to pull the the lock apart (in the same way as you’d open it) and then slowly rotating the dials in turn until they seem to click into place…

More expensive combination locks try to thwart this method with “false gates” that give the impression that you’ve found the correct numbers when in fact you haven’t. However they can often still be decoded with a bit of skill…

But the thing to remember is that virtually no bike thieves have the patience and skill required to pick the more challenging combination locks. And in the street they won’t be able to position the lock in a way that makes even attempting to decode the lock practical.

In fact they are most likely to tackle a decent combination lock in the same way they would attack a decent keyed lock: with brute force.

Cheap Cable Locks and Combinations!

I’ve written many times about how you should never use a cheap cable lock to secure your bicycle. They can be cut in seconds by a small, basic tool that every bike thief carries.

And the thing is: many cheap cable locks use cheap combination mechanisms. So this idea that all combination locks are crappy is reinforced because they’re used on genuinely crappy cable locks. However, it doesn’t mean that all combination locks are crappy!

Wrapping Up

So, yes it’s true: combination locks are less secure than keyed locks. But if you get a decent one with 4 or 5 dials and features that resist the most basic decoding techniques, then in the street, in most instances they are going to offer the same levels of protection as a decent keyed lock.

With that in mind I have compiled a list of some of the better combination locks below. They are all either Sold Secure Silver or equivalent, which is the minimum security level I recommend in a bike lock.

This means they’re suitable for lower risk circumstances (check my full bike lock guide to determine your risk level).

There aren’t any Sold Secure Gold combination locks, presumably because it would be very difficult to make a coded lock that is truly high security.

Header

Model

Metal

Width

Weight

Cans of Coke

Height

Width

Security
Rating

Kryptonite Kryptolok Combo

13 mm

2.30 lb
(1.04 kg)

2.5

8.0 "
(20.3 cm)

4.0 "
(10.2 cm)

Cell
Kryptonite Keeper Combination

7 mm

4.5 lb
(2.04 kg)

5.5

47.2 "
(150 cm)

Cell
Sold Secure Silver
Kryptonite Keeper Combination

9.5 mm

5.85 lb
(2.65 kg)

7

35.4 "
(90 cm)

Cell
Sold Secure Silver
Kryptonite Keeper Combination

9.5 mm

7.35 lb
(3.33 kg)

8.5

47.2 "
(120 cm)

Cell
Sold Secure Silver
OnGuard Bulldog Combo STD

13 mm

2.43 lb
(1.10 kg)

3

9.06 "
(23 cm)

4.53 "
(11.5 cm)

Cell

13 mm

2.15 lb
(0.98 kg)

2.5

5.52 "
(14 cm)

3.55 "
(9 cm)

Cell

13 mm

3.12 lb
(1.42 kg)

3.5

9.46 "
(24 cm)

3.55 "
(9 cm)

Cell
Squire Hammerhead Combi 230

13 mm

3.77 lb
(1.7 kg)

4.5

9.06 "
(23 cm)

4.13 "
(10.5 cm)

Sold Secure Silver
Squire Hammerhead Combi 290

13 mm

3.92 lb
(1.78 kg)

4.5

11.42 "
(29 cm)

4.13 "
(10.5 cm)

Sold Secure Silver
Squire Snaplock 210

12 mm

1.81 lb
(0.82 kg)

2

8.27 "
(21 cm)

4.09 "
(10.4 cm)

Sold Secure Silver
Squire Snaplock 260

12 mm

2.14 lb
(0.97 kg)

2.5

10.24 "
(26 cm)

4.09 "
(10.4 cm)

Sold Secure Silver

About the author 

Carl Ellis

I've had bikes stolen in London, New York and Barcelona. Yep, I was a serial, international, bike theft victim. In 2015 I decided to stop the rot. And not a single bike's been stolen since! Brakes, yes. Bells, yes. But they're another story. Everything I learn, I document on this website. More about my story. Contact me. LinkedIn.

  • It says 3hrs to decode a 4 dial lock. False i found a kryptonite 4 dial lock and got it opened in minutes. There good locks but some skill and good sence of touch makes opening these a piece of cake. They need a new design more difficult to open and i am no locksmith or thief just a automechanic.

    • Hi Rob,

      I mean a maximum of 3 hours. Obviously it’s possible to do it quicker.

      What I mean is that you could try every possible combination in 3 hours.

      So even if the correct combination is the last possible combination of numbers you try, it won’t take more than 3 hours.

      Thanks
      Carl

  • Nice info. One thing I’m wondering about – I’m sitting here with a key stuck in an On-Guard U-lock. I just looked at a bunch of reviews for various U-locks from various brands, and stuck keys or stuck locking mechanisms seems to be one of the most common complaints. My U-lock is now useless, since I can’t get the key out. So I’m wondering if a combination U-lock would possibly avoid this problem.

    • That’s bad news Bryan! Have you tried the tips on the how to fix a jammed bike lock page?

      For sure, you obviously can’t get a key stuck in a combination bike lock as there is no key!

      However, the combination dials can get stuck and that could also prevent you opening the lock.

      I know it’s not much use to you now, but the best advise I can give you is to regularly clean and lubricate you lock, whether that’s a keyed or combination version.

  • hello guys it seems there is worse than cutting locks with tools actually i took all day searching and found it become nightmare thought even sell my lovely bike because what i watched is disaster people needs just a small tool just one tool to open the most famous locks without attention or long time or any problems i canceled order on amazon after that was looking for decent lock with chain but i found someone on reviews post the picking of it what a shock i got so what now is it important to get a locks that contains a unique shape of keys i mean what about keys with this shape is good https://pbs.twimg.com/media/EooeN1tXEAAN_iQ.jpg does it better than others to avoid picking damn its like the thief had the real key??!! i am so confused and in hours replaced the same order again after canceled it is there a real solution??!! the strange that the guy who post the review of picking the lock was also at the same time salute the lock as if he didnt see the lock opened in max 30 seconds without any kind of force!!

    • Hi Muftakis,

      I’m not sure exactly what tools you’re talking about.

      But if you buy a modern lock from Kryptonite, Abus, or any of the other major lock brands, they are not easy to pick.

      And bike thieves don’t usually pick locks anyway.

      So don’t worry! Post a link of the lock you were going to buy and I will tell if it’s any good.

      Thanks

      Carl

  • My cable lock combination stopped unlocking the lock…does a ratcheting cable cutter work the best the others didn’t. Thank you says:

    Hi , I’m Vance,
    My cable lock refuses to open. The cable is very tough not just any table cutter will open them I have not tried the ratcheting cable cutter I know this would be bad news for a crook but it’s my own bike I can’t get to every morning I never knew that a cable combination lock combination would one day just stop working blame it on the devil right. Help

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