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A Combination Bike Lock: Is it really less secure?

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). However, I’d advise caution with the Squire Snaplock which I’ve heard is relatively easy to prize open!

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.

 ModelThicknessWeightCans of coke weightHeightWidthSold Secure Silver?
Kryptonite Kryptolok ComboKryptonite KryptoLok
Combo
13 mm2.30 lb
(1.04 kg)
2.58.0"
(20.3 cm)
4.0"
(10.2 cm)
No
Kryptonite Keeper CombinationKryptonite Keeper 712 Combo7 mm4.5 lb
(2.04 kg)
5.547.2"
(150 cm)
Yes
Kryptonite Kryptolok Chain ComboKryptonite Kryptolok 990 Combo 909.5 mm5.85 lb
(2.65 kg)
735.4"
(90 cm)
Yes
Kryptonite Kryptolok Chain ComboKryptonite Kryptolok 912 Combo 1209.5 mm7.35 lb
(3.33 kg)
8.547.2"
(120 cm)
Yes
OnGuard Bulldog Combo STDOnGuard Bulldog Combo STD13 mm2.43 lb
(1.10 kg)
3 9.06"
(23 cm)
4.53"
(11.5 cm)
No
OnGuard Bulldog Combo MiniOnGuard Bulldog Combo Mini13 mm2.15 lb
(0.98 kg)
2.5 5.52"
(14 cm)
3.55"
(9 cm)
No
OnGuard Bulldog Combo Mini LSOnGuard Bulldog Combo Mini LS13 mm3.12 lb
(1.42 kg)
3.59.46”"
(24 cm)
3.55"
(9 cm)
No
Squire Hammerhead Combi 230Squire Hammerhead Combi 23013 mm3.77 lb
(1.7 kg)
4.59.06"
(23 cm)
4.13"
(10.5 cm)
Yes
Squire Hammerhead Combi 290Squire Hammerhead Combi 29013 mm3.92 lb
(1.78 kg)
4.511.42"
(29 cm)
4.13"
(10.5 cm)
Yes
Squire Snaplock 210Squire Snaplok 21012 mm1.81 lb
(0.82 kg)
28.27"
(21 cm)
4.09"
(10.4 cm)
Yes
Squire Snaplock 260Squire Snaplok 26012 mm2.14 lb
(0.97 kg)
2.510.24"
(26 cm)
4.09"
(10.4 cm)
Yes

The Foldylock Clipster: even easier to carry!

I’m a big fan of the Foldylock Compact. It’s light, easy to use and offers very reasonable Sold Secure Silver levels of protection for medium risk situations.

Folded Foldylock
Folded Foldylock Compact

It’s also very easy to carry. The frame mount that comes with the Foldylock can screw directly into those holes on your down tube that are designed for a water bottle cradle. This will hold your lock in place securely while you ride around and then release it quickly and easily when you need to lock up.

Foldylock attached with water bottle screws
Foldylock attached with water bottle screws

But some people don’t like frame mounts! They’re not the prettiest addition to your bike. And maybe you don’t have room for one anyway? Maybe you’re already using your water bottle cradle holes to carry a water bottle? Or maybe you don’t have water bottle cradle holes at all?

I know I don’t. So when I tested my Foldylock I used (the included) velcro straps to secure the lock to the frame of my favorite beater bike. And although they work fine, the unused lengths of strap flapped about in a slightly annoying way.

Foldylock attached with Velcro straps
Foldylock attached with Velcro straps

So I was very happy to hear that the Foldylock was now available in a variation called the Clipster. The lock itself is identical to the original Foldylock Compact. But it includes a built in clip that you can attach to your belt, pocket, bag (or anything else it will fit over).

Foldylock Clipster on belt

It also comes with a thick elastic band to go over the bottom of the lock to stop the bars moving about while your riding.

Foldylock Clipster
The Clipster folded up

The great thing about the Clipster (and this is something which I didn’t really think about until I started using it), is that, even though the original frame mount was really easy to use, the time it takes to lock and unlock your bike is still significantly reduced when you carry your lock clipped to your belt.

Fold up, clip on. Clip off, unfold. Super easy. And super quick.

So not only will your bike be unencumbered by yet more detritus (the frame mount), you’ll also have a smoother, faster locking experience. What’s not to like?

See my full review of the Foldylock Compact for more details on how secure this lock is and how it compares to other locks. If you like the look of it, the Clipster is available from both the Foldylock website and Amazon .

And if your still unsure about how to choose the best bike lock for your individual circumstances, check out my easy step by step guide here.