The TMD chain lock was launched just recently and its design sets it apart significantly from traditional bike locks. Instead of using a conventional key, it relies on a Bluetooth connection to a smartphone, combines this with a built-in alarm system and even allows you to share access with other people. On top of that, firmware updates enable new features to be added at a later date.
That sounds like an interesting idea — but how well does a lock like this actually work in everyday life? That’s exactly what we put to the test.
Excellent build quality
Right from the moment you unpack it, it’s obvious that TMD has placed great emphasis on build quality and the choice of materials. Both give you the feeling that you’re holding a durable product in your hands — which is to be expected, given the price of 249 euros for the 110 cm version tested here.
The chain is encased in a soft silicone sleeve with a woven cover, which reliably protects the frame from scratches whilst also preventing the lock from making an annoying rattling noise whilst cycling. Its high flexibility is another positive feature. Despite its hardened steel core, the chain can be bent quite tightly, making it straightforward to secure in practice.
At 1.7 kilograms, the weight matches the manufacturer’s specifications exactly — and given the solid steel core and the integrated electronics, this figure seems entirely reasonable. The locking mechanism, on the other hand, is considerably larger. This is hardly surprising, as it houses not only the electrically controlled locking mechanism but also the battery, speaker and the entire electronic system. It should be noted in this context that, on bikes with compact 20-inch wheels, the lock can sometimes be difficult to thread through the spokes. On bikes with standard wheel sizes, however, this was not an issue during testing.
The battery life also made a very good impression. After around a month of regular use, the charge level had dropped by only about ten per cent — which is well within the manufacturer’s stated battery life of up to nine months. Charging is carried out via a special magnetic connector, which is pleasantly easy to use whilst also offering good protection against moisture. Although a USB-C port would have been more versatile for everyday use, the decision to opt for the proprietary connector is nevertheless understandable given the requirements for weather resistance.
The only control on the lock is a button surrounded by an LED ring. Its clearly defined pressure point ensures that it can be operated reliably even when wet.
Convenience instead of a bunch of keys
However, the TMD chain lock really comes into its own in everyday use. It connects automatically to your smartphone via Bluetooth and detects when it is nearby, without you having to take it out of your trouser or jacket pocket. A single press of the button is then all it takes for a small electric motor to unlock the lock.
This system worked reliably throughout the entire test period. Occasionally, however, the lock does take a brief moment to connect via Bluetooth. A blue flash of the LED ring does indicate that the smartphone has been detected. However, as this signal appears only for an instant, it is sometimes unclear whether the connection has already been established or is still being set up. A continuously lit status indicator would have been the more practical solution here.
Apart from that, the operating concept is impressive across the board. After just a short while, you won’t want to be without the convenience of simply leaving your smartphone in your pocket and still managing perfectly well without a bunch of keys. Ultimately, that is precisely where this lock’s greatest added value lies.
Smart features without having to use your smartphone all the time
The accompanying app is at least as well thought-out as the hardware itself. It usefully expands the lock’s range of functions and allows new features to be added via firmware updates – an option that TMD has already made use of. For example, a silent mode is now available: whilst the lock initially acknowledged every press of the button with an audible signal, it can now be operated silently — and thus much more discreetly — if desired.
In addition, it’s easy to add other users to the lock. This feature proves particularly handy in everyday family life or when several people share a cargo bike.
But best of all: once it’s set up and configured to your liking, the app hardly plays a part in your day-to-day life. To access it each day, all you need to do is carry your smartphone with you — it can stay comfortably in your pocket whilst you’re out and about. It is precisely this combination of extensive features and straightforward operation that makes the system so user-friendly.
Well prepared for unexpected situations
Naturally, the question arises as to what happens if the smartphone runs out of battery or stops working altogether. The lock has an emergency mode for precisely this scenario. A pre-set four-digit code can be entered directly using the button. The LED ring displays four colours in succession, each of which corresponds to a specific numerical value. The code is entered by pressing the appropriate buttons, and the lock is then unlocked.
Although this method is considerably more fiddly than the normal procedure, it serves its purpose reliably as a stopgap solution. Above all, it ensures that you can always get back to your bike, even without a working smartphone.
An alarm attracts attention
The security features also include a built-in alarm system, which can be activated by double-clicking the button. A brief flash of white light from the LED ring confirms that the system has been activated. If the built-in sensor subsequently detects any suspicious movement, an early warning is issued before the actual alarm is triggered at a volume of 100 decibels.
In testing, the signal proved to be extremely loud and is likely to attract sufficient attention in the event of an attempted theft. At the same time, the system prevents false alarms caused by the owner themselves – because as soon as the lock connects to the authorised smartphone and is unlocked, the alarm function deactivates automatically.
Conclusion
In our test, the TMD chain lock demonstrates just how convenient a modern, keyless lock can be in everyday life. The automatic unlocking feature works reliably and makes the daily process of locking and unlocking noticeably more convenient, even if the Bluetooth connection occasionally takes a brief moment to establish. Added to this are an impressive battery life, the ability to easily share access with other people, and an effective alarm function. The only major drawback is the rather high price. At the same time, the lock currently offers a combination of keyless operation, an alarm system and app connectivity for which there are hardly any comparable alternatives on the market. Anyone prepared to pay this premium will receive a technically well-designed product that genuinely makes everyday cycling a good deal more convenient.
As well as the 110 cm version we tested, the TMD chain lock is also available in 70 cm and 160 cm lengths – each in navy, beige and black. Prices start at 229 euros for the smallest model – available directly here from TMD or from selected specialist retailers.
