Zefal K-Traz U17 Review: Understated Reliability!

Zefal K-Traz U17 Review: Understated Reliability!

Last Updated on April 4, 2024 0 Comments

Zefal K-Traz U17 bike lock

Zefal K-Traz U17

My score:

Rating: 4 stars

Check price:

Shackle thickness:

14 mm


3.24 lb (1.47 kg)

Size (internal):

9.1 x 4.5"
(23 x 11.5 cm)

Zefal rating:


Other Security Ratings:

Sold Secure Gold

After several weeks of testing and writing about crazy new bike locks, it was good to get back to a fairly traditional, standard size u-lock in the Zefal K-Traz U17.

These days, people are getting more and more carried away with smart locks, GPS tracking and all sorts of technical innovation.

But surely all we really want is a lock that’s strong enough to stop our bike from being stolen, easy to carry around and easy to fasten around our bike. And all for a reasonable price, that doesn’t rival the cost of our bike!

Unboxing the Zefal K-Traz U17

Unboxing the Zefal K-Traz U17

And this is what the Zefal K-Traz U17 is trying to offer us. A no-nonsense, traditional u-lock that gets the basic things right.

How well does it do that? Well, keep reading and we’ll find out. I’ve been using the K-Traz U17 for a couple of weeks, and we’ll look at how secure it is, how easy it is to carry around and how easy it is to use on a daily basis.

And at the end I’ll suggest some alternative locks, just in case it’s not right for you… 

How secure is the Zefal K-Trauz U17

The K-Traz U17 is Zefal’s most secure bike lock, and they give it an in house security rating of 17/20. It’s also the only Zefal lock which has a Sold Secure Gold rating, which means it’s suitable for high risk circumstances.

It features a 14 mm shackle made from high resistance steel, which uses a “quadruple locking” system.

14 mm shackle on the Zefal K-Traz U17

The Zefal K-Traz U17 features a 14 mm shackle

What is a “quadruple locking system”? Basically it means that the ends of the shackle have 2 cuts in them (one on each side), rather than the 1 cut you find on most u-locks...

The quadruple locking shackle

Zefal quadruple locking shackle vs Kryptonite double locking shackle

When you lock the shackle into the body, the mechanism fastens into the ends of the shackle on both sides (into both cuts) of each arm. So there’s four connections in all, hence the “quadruple locking”.

Th body locks into the shackle on two sides

The body locks into the shackle on two sides

The idea is that this gives the shackle a stronger connection with the body of the lock, making it more secure.

As far as I know, the only other other company offering this kind of quadruple locking is OnGuard who use it on their higher security Pitbull and Brute ranges.

However, how much extra security "quadruple locking" offers is a moot point. There’s extra connection (and therefore you’d imagine extra stability). But the ends of the shackle are also thinner, owing to the extra cuts (perhaps leading to more weakness).

Certainly, there are plenty of very secure locks that don’t use quadruple locking mechanisms!

But there’s no doubt the K-Traz is also a pretty secure lock. The 14 mm thick shackle can theoretically be cropped by the biggest bolt cutters. But the thief would need to know what he’s doing and be able to get the lock in a favourable position.

Zefal K-Traz U17

Zefal K-Traz U17: it's pretty secure!

And the quadruple locking shackle should also provide plenty of protection from leverage attacks with longer pieces of metal such as scaffolding.

So with the correct locking technique, it should be possible to secure your bike in a way where the K-Traz U17 is unlikely to be defeated by anything but power tools. Which is obviously nice!

How easy is the Zefal K-Traz U17 to carry?

The official weight of the K-Traz U17 is 3.24 lb (1.47 kg), although I weighed it at 2.85 lb (1.29 kg). The official weight probably includes the mount and keys. It’s about average for a 14 mm standard size u-lock.

Weighing the Zefal K-Traz U17

At 2.85 lb (1.29 kg) the K-Traz U17 is about average for a 14 mm u-lock

That’s not to say it’s light. It’s the equivalent of 4 cans of coke. And because it’s a standard size u-lock, it's actually quite big, measuring 9.1" x 4.5" (23 x 11.5 cm). So carrying it around could be a bit of an issue.

The Zefal K-Traz U17 and Coke can

The K-Traz U17 is around the same weight as 4 cans of Coke

You could slip it your backpack, saddlebag or pannier quite easily and it’s not so heavy that it’s going to be a problem for most people. Or there are other places to put your lock when riding.

Zefal K-Traz U17 in saddlebag

The Zefal K-Traz U17 slips into into my saddlebag easily

But the K-Traz U17 also comes with a frame mount that you can attach to numerous places on your bike frame, as long as the tubes are between 20 and 80 mm in diameter.

Zefal K-Traz U17 frame mount

Zefal K-Traz U17 frame mount

Now, it’s certainly not the fanciest frame mount I’ve ever seen. But it’s actually really easy to attach to your bike and for me it worked really well. I think I had it on the bike with the u-lock clipping in and out in less than a couple of minutes.

The frame mount is identical to the OnGuard frame mount (bar the colour of the button that releases the lock). And as I’ve said before I much prefer this mount to the Kryptonite mount.

Zefal K-Traz U17 frame mount pieces

2 pieces and 2 sets of screws (longer ones for bigger frames)

You get two sets of screws (one set is longer for fatter frames). And there are  two pieces of the mount. Simply screw one piece into the other (with your frame in the middle). Tighten. And you’re ready to go!

You’ll just need a Philips screwdriver. Plus a small hex key if you want to adjust the position of the bar on the lock that clips into the mount.

The screws inside the centre of the frame mount allow you to turn the bit that the lock clips into so that the lock sits in the optimal position wherever it is on your frame...

Zefal K-Traz U17 frame adjustment screws

Tighten these screws if the frame mount seems a bit wobbly (they´re also used to rotate it)

It’s worth noting: if the frame mount seems a bit unstable, tighten these screws and that should sort out any wobbles or rattles.

For regular bikes in urban environments, I think this frame mount is great. Easy to install. Easy to use. And while I was riding around the city it kept the K-Traz U17 firmly in place.

How easy is the K-Traz U17 to use?

The K-Traz U17 is a standard size u-lock. But it’s just slightly longer and wider than a lot of other standard size u-locks, measuring 9.1" x 4.5" (23 x 11.5 cm).

And that means it’s going to give you loads of locking options in the average town or city...

Locking the frame and back wheel

Locking the frame and back wheel is easy

In a bike rack, you’ll be able to get it around your frame and rear wheel (or front wheel) in most situations and for most bike types. And the extra bit of width gives it enough to go around some lampposts too.

Locking to a lamppost

You can even lock to a lamppost (I wouldn't recommend around the top tube though)

The lock clips in and out of the frame mount quickly and easily. The generous internal dimensions mean securing your bike is usually a pain free experience! And the shackle is covered in a hard rubber coating that will protect your paintwork.

You get three keys with the K-Traz U17. And they’re internally cut, sidewinder keys which are more difficult to replicate and therefore theoretically more secure (although I’ve never heard of thieves replicating keys!)

You get 3 keys with the K-Traz U17

You get 3 keys with the K-Traz U17

You also gets a key code which enables you to replace lost or damaged keys, as and when you need them. All pretty standard stuff.

The key hole has an internal metal guard to protect the locking mechanism from the weather and street grime which might cause it to jam. From a usability perspective, these internal guards are great…

Pushing the key into the hole gently forces open the guard, so you don’t really notice it’s there. Compare this with external covers, where you have to move them out of the way, before you can insert the key.

Internal key hole cover

An internal metal guard protects the mechanism

However, if they break (sometimes the springs go), the internal guards can be a bit of a nightmare. A broken internal guard can prevent you inserting the key altogether and it can be difficult to remove the guard and resolve the issue.

This one’s metal, so hopefully it will be more robust than the plastic one on a different lock that broke last week, causing me all sorts of problems!

As ever, the key to longevity with bike locks is maintenance! Giving the mechanism and shackle and good clean and lubrication every few months will massively reduce the chances of the lock starting to stick.

Clean the mechanism with WD-40. And then lubricate it with a Teflon based product such Finish Line or TriFlow. Then smear White Lithium Grease on the ends of the shackle. This should keep the K-Traz U17 working smoothly for years to come!

Is the K-Traz U17 good value for money?

Traditional, no nonsense u-locks like the K-Traz U17 stand or fall based on their price. There’s not a lot of innovation that would justify a higher price with the K-Traz U17 (unless you count the quadruple locking shackle).

It’s a straightforward u-lock that you’d buy to do a straightforward job (protecting your bike), with as little fuss as possible. And ideally, for as little money as possible!

And the good news is that the K-Traz U17 is really cheap! At the time of review it’s even cheaper than the equivalent OnGuard u-lock, which is in fact the lock that the K-Traz U17 most closely resembles.

And OnGuard locks are also really cheap. So yes, to me, the K-Traz U17 seems very good value for money!

Wrapping Up

With all the talk of smart bike locks with GPS, keyless locking and alarms, it’s easy to forget about the basic, fundamental requirements of a bike lock.

I just want a lock that adequately protects my bike, that’s easy to use, and easy to carry around. And I don’t think that bike lock should cost the same amount of money as I’d get for my bike, if I sold it!

Most people are not riding super expensive bikes. They’re riding functional workhorses to get from A to B. And the idea that they should spend the same amount of money on a lock as they would on a bike is ridiculous.

So cheap bike locks are important. But they need to be secure. And they need to be reliable. And the Zefal K-Traz U17 fulfils those needs really well.

Zefal K-Traz U17 on bike

The Zefal K-Traz U17 does the basics really well

It’s Sold Secure Gold so you know it’s pretty secure. It’s really cheap. And it does it’s job quietly and efficiently.

The shackle locks into the body smoothly. The keys turn freely. And the mechanism is protected by an internal metal cover that seems robust. The standard size shackle will give you loads of locking options. And the frame mount is easy to fit and works well in urban environments.

For me, the Zefal K-Traz U17 provides understated value. It does all the basics right for a very competitive price.

What’s not to like?

Zefal K-Traz U17 U-lock

After several weeks of testing and writing about crazy new bike locks, it was good to get back to a fairly traditional, standard size u-lock in the Zefal K-Traz U17.

Product Brand: Zefal

Editor's Rating:

Well, I can think of a few things that you might want, that the Zefal K-Traz U17 doesn’t provide. So let’s look at some alternatives if it’s not the right lock for you...

Alternatives to the Zefal K-Traz U17

Whether you're looking for something smaller, something more secure or something that's easier to carry, there are plenty of alternatives to the K-Traz U17.

Looking for something smaller?

OnGuard Pitbull Mini

Unfortunately, Zefal don't make a smaller version of the K-Traz U17.

However, OnGuard locks are very similar to Zefals. And they're also very cheap!

The OnGuard Pitbull Mini [Amazon] features a quadruple locking 14 mm shackle just like the K-Traz U17. And it's also Sold Secure Gold.

But it's much shorter at 5.52" (14 cm) and a little bit narrower too at 3.55" (9 cm). This also makes it a bit, lighter at 3.13 lb (1.42 kg).

This limited weight saving may make you question why you'd want a smaller lock. But smaller locks have some benefits beyond weight...

The smaller shackle will give you a tighter fit when you're locking up. And although this means less locking opportunities for you, it also make it more secure.

Plus the smaller size will give you more stability if you choose to carry it using the frame mount (which is identical to the one that comes with the Zefal). And if you carry it a bag instead, it will obviously take up less room.

So if you like the price of the K-Traz U17 but fancy something a bit more compact, check out the OnGuard Pitbull Mini [Amazon]!

Looking for something more secure?

OnGuard Pitbull Standard

It's hard to tell how secure the K-Traz U17 is in relation to it's nearest rival, the OnGuard Pitbull Standard.

They're very similar in form. But the Pitbull is Sold Secure Diamond rather than Gold. This could be because the Zefal hasn't been tested yet for Diamond, but I suspect not!

However, to be sure you're getting a significant security boost from the K-Traz U17. I recommend going for the OnGuard Brute Standard [Amazon].

It's an absolute beast, with a 16.8 mm shackle!

And weighing in at 4.67 lb (2.12 kg), it's 44% heavier than the K-Traz U17! It's one of the most secure bike locks available though, and also has a Sold Secure Diamond rating to prove it.

So if you're looking for something that you can be sure will offer you more protection than the K-Traz U17, but is still incredible value for money, it's hard to beat the OnGuard Brute Standard. 

Looking for something that's easier to carry?

Trelock FS 500 Toro

The K-Traz U17 is not so heavy or bulky. And it cones with a decent frame mount. But some people will want a lock that's just a bit easier to carry.

Folding locks are undoubtedly the easiest locks to carry around, whether they're attached to your frame or thrown in a bag.

But folding locks are expensive and there's only two folding locks with the same Sold Secure Gold rating as the K-Traz U17.

One is the Abus Bordo 6500. The other is the Trelock FS 500 Toro. I'm recommending the Trelock lock here, simply because it's much cheaper!

It's still much more expensive than the K-Traz U17 though! However, it will be be a bit easier to carry around.

It weighs 3.48 lb (1.58 kg), so it is a little bit heavier than the K-Traz U17, (folding locks are generally heavier than their equivalent u-locks).

But it folds down into a incredibly compact package, that's easy to fit in any bag and will also be less troublesome than any u-lock if you use it with the frame mount (owing to the how close the folded up lock sits to the frame).

So if your looking for lock that's just as secure as the K-Traz U17, but one that's easier to carry around (and you're prepared to pay a little bit more), the Trelock FS 500 Toro [Amazon] is a great choice!

And if you're not sure what security level you need, or what type of lock suits your circumstances, check out by simple, 3 step guide, that will show you how to choose the best bike lock for you!

Zefal K-Traz U17 Specs

Zefal K-Traz U17 bike lock

Zefal K-Traz U17

My score:

Rating: 4 stars

Check price:

Shackle thickness:

14 mm


3.24 lb (1.47 kg)

Size (internal):

9.1 x 4.5"
(23 x 11.5 cm)

Zefal rating:


Other Security Ratings:

Sold Secure Gold

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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.

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