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Zefal K-Traz U13 S Review – A Good Choice of D Lock?

10 min read

Zefal K-Traz U13 S Review

Zéfal’s K-Traz range is a popular, budget range of bike locks. Throughout this article I’ll be reviewing the Zefal K-Traz U13 S, and will walk you through its strengths and weaknesses.

Zéfal have been the brains behind many cycling inventions that have changed the way we ride, but just how secure are their bike locks and are they worth your money?

The U13 S is visually similar to the OnGuard Pitbull Mini, but how does it compare and which is the better option?

Let’s find out!

Overview - Is the Zefal K-Traz U13 S a Good Bike Lock?​

Zefal K-Traz U13 S Review



Today’s Best Deals:


Security Rating – Sold Secure Silver
Weight – 0.9kg kg (2.2lb)
Shackle Dimensions – 9 x 14cm (3.5 x 5.5″)
Shackle Thickness – 13mm Hardened Steel
Warranty – 2 Years

The K-Traz U13 S isn’t the most secure bike lock on the market but is a great option for those on a tighter budget, or with a less expensive bike.

Weighing only 2lb (0.9kg) it’s lightweight, quad bolted and resistant to all forms of attack. Due to its lighter weight, it’s easily transported on the mount supplied, or takes up minimal space in a backpack.

If you commute and don’t want to carry around a super heavy lock but require a decent level of security at the same time, the U13 S is a great choice.

Table of Contents
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    How Secure Is The Zefal K-Traz U13 S?

    The K-Traz U13 S is a Sold Secure Silver rated D Lock. The Sold Secure Silver rating means that the U13 S offers a compromise between security and cost.

    Zefal rated the U13 S at 13/20 on their in-house security scale and say that this mini D Lock is suitable for “use in high risk areas”. Personally, I think the K-Traz U13 S can be used in high risk areas, but this will depend on the value of the bike you’re securing.

    Zefal K-Traz U13 S Security Ratings

    The U13 S has a 13mm thick shackle, which is made from high resistance steel. 13mm is not thick enough to be considered bolt cutter proof, but because the shackle is quad bolted, it will do a good job at resisting most forms of attack.

    Zefal use a very similar quad locking mechanism to OnGuard, which provides good protection against twist and hydraulic attacks. Normally, locks of this price are single bolted which leaves them far more vulnerable to bolt cutter attacks.

    The outer shell of the Zéfal K-Traz U13 S is made from hardened steel. Its Bold colours also make the U13 S stand out when securing your bike and will make thieves think twice before trying anything funny.

    How Practical is the Zefal K-Traz U13 S?

    Weight and Size

    As I’ve covered, the U13 S is a smaller version of the U13. Its shackle measures 3.5” x 5.5” (9cm x 14cm) which is definitely on the small side.

    Using my town bike I was unable to easily secure my rear wheel and frame to a bike stand at the same time using my regular locking method. But don’t worry, using the Sheldon Brown locking method, you’re able to effectively secure your frame and rear wheel. 

    Later on I’ll explain just how to do this. 

    Zefal K-Traz U13 Locking back wheel

    Weighing in at a tiny 2lb (0.9kg) the U13 S is extremely lightweight. I think the U13 S’s lighter weight makes up for what this mini D Lock lacks in security.

    The general rule of thumb you can follow with bike locks is, the thicker the shackle, the more secure the lock. Unfortunately, this means that the locks which offer good levels of security and normally much heavier due to their larger shackle diameter.

    Fortunately, Zéfal have found a sweet spot with the U13 S which offers a good blend of security and practicality.

    Zefal K-Traz U13 S Specs
    Weight: 2lb (0.9kg)
    Width: 3.5" (9 cm)
    Length: 5.5" (14 cm) 
    Shackle Diameter & Material: 13mm Hardened Steel
    Sold Secure Rating: Sold Secure Silver

    Mounting System

    The mount supplied with the Zefal K-Traz U13 S is identical to the mount you receive with OnGuard’s range of D Locks. It’s made from plastic and feels rather flimsy.

    Because the U13 S is available at such a budget price, I don’t think it’s surprising that manufacturing costs have been cut on its accessories.

    The multi-position mount fits frames of 20-80mm diameter, which does mean it struggles to attach to thicker bike frames. Attaching the mount is fiddly and you’ll require a screwdriver to get it fixed in place.

    How to mount the Zefal K-Traz U13 S
    Once the mount is attached, the lock is mounted by inserting horizontally and twisting until vertical. The red plastic button seen on top of the mount is then used to remove the lock.

    The mount is operated by a spring-loaded button, which is stiff to use at first and originally made the U13 S hard to remove once mounted. Fortunately, after using the mount several times, the plastic edges became rounded and the mount operated more fluidly.

    If the mount won’t fit your bike’s frame, or you’d rather not use one, this mini D Lock is easy to transport in other ways.

    My favourite way of transporting the U13 S was by threading it underneath my belt. This provided easy access to the lock whilst I was out cycling and was more convenient than using the mounting system.

    Thanks to its smaller size, the K-Traz U13 S takes up minimal space in a rucksack and because it’s so lightweight, you won’t have an uncomfortable time riding with it on your back.


    Quality & Maintenance

    Whilst the K-Traz U13 S doesn’t feature many plastic parts, the use of cheaper materials and manufacturing techniques is evident. Upon taking the U13 S out of its box I noticed that there was already a small amount of rust on the bottom of its shackle.

    The shackle is coated in an anti-rust paint, which prevents water from coming into contact with the metal underneath. However, if this paint is chipped away (which is unavoidable over time), it appears that the metal underneath corrodes easily.

    Corrosion can be prevented by carrying out basic maintenance, so this isn’t a major flaw, but the U13 S will require more maintenance than a more premium lock.

    Rusty D lock
    Whilst it's only a tiny amount of rust, you wouldn't expect to find any on a brand new product.
    A small amount of grease is all that's needed to stop this worsening.

    I’ve put together a guide which will help you increase the usable life of any bike lock, have a read if you’re interested.

    Like most D locks, the shackle also has a rubber outer sleeve which prevents the U13 S from scratching your bike’s paintwork.

    Locking Mechanism & Operation

    I was pleasantly surprised by the locking mechanism of the U13 S. Its operation is smooth and I’m yet to have any issues when locking/unlocking it.

    I had a few issues with D Locks from the OnGuard range which use a similar mechanism, but Zefal appear to have avoided these problems.

    The U13 S is supplied with three sidewinder keys, which are straightforward to use, but don’t have an integrated LED like the OnGuard Brute and Pitbull. If you loose your keys and need replacements cut, you’ll be able to do so with the key code card provided.

    Zefal U13 S Keyhole cover

    A manually operated sliding keyhole cover will help to keep unwanted dust and debris out from inside the U13 S’s locking mechanism. Keyhole covers are also good for keeping the locking mechanism dry and free from moisture if locked outside during bad weather.

    The quad bolt mechanism is slightly spring-loaded. This means, when the key is inserted and turned half way, the spring engages and slides the bolts into position around the shackle. This isn’t strictly necessary, but definitely increases the locks ease of use.

    Operation is an area that many cheaper locks normally struggle with, but happens to be one of the U13 S excels in. As I’ve covered, with regular maintenance the U13 S will serve you well.

    Zefal U13 S Best Bits

    • 13mm Hardened Steel Shackle
    • Anti-pick and drill 
    • Double bolted shackle
    • Key replacement scheme
    • Bright colours deter thieves 

    Best Way to Use the Zefal K-Traz U13 S

    Normally I’d recommend using a D Lock to secure your bike’s frame and rear wheel. This wasn’t possible with the U13 S because its shackle was slightly too short. Instead, the Sheldon Brown locking method is a good alternative.

    Simply lock the K-Traz U13 around your rear wheel’s rim and to an immovable object. This method will prevent a bike thief from running off with your wheel and will also keep your frame secure.

    Sheldon Brown locking method using Zefal K-Traz U13 S
    When using the Sheldon Brown locking method, it's important to lock the rim of your wheel. Never lock around the spokes

    If a thief attempts to remove your back wheel, the lock won’t be able to be pulled through the chain/seat stays. You can learn more about the Sheldon Brown locking technique here.

    Using the Sheldon brown technique alongside a cable extension is the best way to secure your bike with the K-Traz U13 S. Unfortunately the U13 S isn’t supplied with an extension, but these can be purchased for a very affordable price.

    Zefal Warranty

    Zéfal offer a two-year warranty on all of their products. This warranty will cover you in case of manufacturing/workmanship defects. Within the two years if you have any issues with your lock, get in contact with Zéfal, who will be glad to help.

    It’s worth noting that you won’t be covered for general wear and tear or misuse of any products.  

    I haven’t had to claim against this warranty, so can’t comment on how easy this procedure is. Other brands such as Kryptonite and OnGuard offer a lifetime warranty against manufacturing and workmanship defects, which makes this warranty look slightly stingy.

    OnGuard and Kryptonite both also offer Anti-Theft Protection, another service that Zefal don’t provide. 

    For the price this D Lock costs, you can’t really complain though.

    Included in the Box

    • U13 S UnboxedZefal K-Traz U13 S
    • Mounting system (with instructions)
    • 3 x Zefal ergonomic keys
    • Keycode card

    How Much Does the Zefal K-Traz U13 S Cost?

    There’s no denying that the Zefal U13 S is sold at a very reasonable price [Amazon]. It’s affordable to every cyclist and will do a great job at securing most bikes.

    There are other Sold Secure Silver D Locks such as the OnGuard Bulldog Mini that retail at a similar price.

    If you’re looking for a more secure bike lock, the OnGuard Brute is a great choice, which is still affordable on a budget and provides the highest level of bicycle security (Sold Secure Diamond).

    How Does the U13 S Compare to Other Bike Locks?

    Kryptonite Kryptolok Mini-7 with Flex

    A Better Quality, Sold Secure Gold Mini D Lock




    Another Sold Secure Gold bike lock available at a reasonable price. The Kryptolok Mini 7 uses Kryptonite’s Hardened Double Deadbolt to secure either end of the shackle.

    This lock is more premium than the U13, and will last you longer, with less maintenance required, thanks to better quality materials used to produce these D Locks.

    With the Kryptolok you’ll receive access to Kryptonite’s Key Safe Program as well as receiving cover for their Anti-theft protection offer (registration required).

    Ultimately, a more premium bike lock that will cost slightly more, but will far outperform the U13. You can read more about the 

    OnGuard Brute

    A Stronger Option, Still Affordable on a Budget

    Onguard Brute Sold Secure Gold Bike Lock



    The OnGuard Brute is OnGuard’s most secure bike lock. It boasts a whopping 16.8mm hardened steel shackle, which makes it impossible to crop by hand.

    The Brute uses a similar locking mechanism to Zefal, the X4P Quattro. This quad bolting mechanism repels twist and hydraulic attacks with ease.

    The Brute STD 8001 offers a larger shackle than the U13 S measuring 4.53″ x 7.96″ (11.1cm x 26cm). There are two other models of the Brute available, the Brute LS (long shackle – increased locking area) and the Brute Mini.

    The Brute doesn’t cost much [Amazon] more than the U13 S and is definitely worth considering.

    If you’re interested in a more secure, yet budget bike lock, you can read more about the OnGuard Brute here.

    Zefal K-Traz U17

    A Super Affordable Sold Secure Gold Rated D Lock



    Today’s Best Deals:

    The Zéfal K-Traz U17 is Zéfal’s most secure bike lock. They rated it at 17/20 on their in-house security scale, which make it suitable for “use in extremely high risk areas”.

    Its Sold Secure Gold rated, quad bolted, and highly resistant to all forms of attack. The U17 is similar to the U13 but is more secure thanks to its thicker 14mm hardened steel shackle.

    If you like the look of the U13 but have invested a reasonable sum of money into your bike, the K-Traz U17 should serve you well, but I’d also recommend checking out the best cheap bike locks. It’s also supplied with a cable extension which you won’t receive with the U13.

    You can read my extensive review of the U17 here.

    Who Are Zefal?

    Zéfal is a French company that was founded in 1880. Shortly after, they invented the Presta Valve, one of the most popular valve types for inner tubes to this day. Since 1880 Zéfal have carried on innovating and have produced and manufactured many incredible products.

    It wasn’t until after 2014 that they began manufacturing bicycle locks. They now offer a wide range of different locks, most of which have been submitted for testing with approved security accreditation bodies.

    Summary - A Very Reasonably Priced Mid Security Bike Lock

    I’ve enjoyed reviewing the U13 S. The K-Traz U13 S is the smaller version of the K-Traz U13 and offers Sold Secure Silver protection.  It doesn’t have many flashy features; but it consistently performs well and I didn’t find any issues with its usability.

    The mount supplied with the Zefal K-Traz U13 S is cheap and flimsy, but you can’t expect much more from a budget bike lock.

    I would recommend this lock for cyclists with relatively cheap bikes. Whilst its shackle is 13mm thick it’s not bolt cutter proof and could be cropped by a large pair of bolt cutters.

    If you’re looking for a lightweight, mid security bike lock, sold at a budget price, look no further. This U13 S is a good choice.

    However, if you’re looking for something more secure, check out one of the 8 best bike locks or the best cheap bike locks for some great alternatives.

    And as always, lock it, or lose it!

    Author of This Post:
    Picture of James Grear (Lead Editor)
    James Grear (Lead Editor)

    Understanding how devastating it is to have a bike stolen, I've researched & immersed myself in the world of bicycle security since 2013.

    I then built BikeLockWiki in 2019 to share everything I'd learned with the worldwide cycling community so that cyclists can improve their bike security skills and make informed decisions when purchasing new products and services.

    Learn More about Me & BikeLockWiki here.

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