Knog Mid Cobber rear light review: Incredible side visibility, but the build quality is lacking

Fortunately for my mental health, it is almost, almost, light when I clock off for the day. That means my opportunities for testing the best bike lights are waning, but there’s still a while until I even consider removing lights from my bike. Even then, daytime running lights are becoming the norm now, so I may not even reach that point. 

A lot of my testing this year has focussed on front lights, but I’ve still been trying a variety of different rear options over the last few months and one that caught my eye more than most - because let’s be real, rear bike lights are functional, but hardly the sort of thing most of us lust after - has been the Knog Mid Cobber. 

I spend a lot of time riding around the city. I do a weekly lap of all the hills each Wednesday night, but I also don’t own a car so I get around on my fixie year-round. Side visibility has been a real focus for me, having had several near misses with cars, and in addition to the magnificent Magicshine SEEMEE 300, the Knog Mid Cobber offers more than most in this department. It’s a brilliant light but isn’t perfect, and is more suited for around town than it is for extended night riding out in the countryside. 

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Design and aesthetics

Most rear bike lights, quite understandably, take the form of one or more rear-facing LED bulbs. The danger is usually from behind you, and because LEDs aren’t laser beams they do throw out some light sideways too in a cone shape. Often you’ll see rear bike lights have windows or cutouts in the side to allow more light to escape sideways, like with the Lezyne Strip Drive Pro 400+. The Magicshine SEEMEE300 projects a large cone of light downwards, which works even better. Taking the slightly more simple approach, the Knog Mid Cobber (the Mummy Bear in the range betwixt the Big Cobber and the Lil Cobber) curves an array of LEDs into a crescent shape, throwing red light directly sideways. 

It’s a disarmingly simple solution that makes me wonder why it’s not been done before. According to the Knog website, it may be because ‘18 factories told us Cobber would be impossible’, but given we’ve put a man on the Moon, have self-driving cars, and have created artificial intelligence convincing enough to begin to erode the fabric of society I suspect this is either hyperbole, or Knog was asking factories usually tied up with producing pencils, shoe leather, or fizzy sweets. 

The curved LED array is almost a perfect semicircle, but as the very distal bulbs also project sideways the effective visibility is a claimed 330º. This is about as wide as you’ll find anywhere and means that if a car (or anything else for that matter) is approaching you side on the driver should see a decent amount of light, akin to what you’d normally see from behind.

The light clips onto your seatpost with a simple rubber O-ring. There’s plenty of room for even very deep seatposts, and there is a replaceable insert to allow it to fit on more aero posts too. 

A single button on top controls everything: Long press to turn on, short press to cycle the 8 different modes, long press to switch it off. The modes are the usual array of solid outputs of varying intensity, along with some more unusual flashing patterns that make use of the curved shape to add more motion that you normally see in rear lights. My favourite was the one that pans a strip of illuminated lights across the face, effectively mimicking a rotating light. Runtimes vary depending on the output, from a claimed 100 hours on eco flash (15 lumens, so very much a ‘get you home’ mode), to 2 hours at 75 lumens full power. With a 170-lumen steady pulse you’re looking at 2.5 hours, and with rolling flash (my favourite) you get 4.5 hours, so more than enough for an each-way commute with time to spare. 

Unusually it doesn’t have a charging port, which undoubtedly helps it achieve an IPX6 waterproof rating, meaning it can be submerged to 1 metre, so more than enough for rear wheel spray without a mudguard. Instead, you pop the seatpost gripper off downwards to reveal a male USB connector - not USB-C, the old type - which you can plug into any USB outlet you see fit. 

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Performance

I cannot fault the light output of the Knog Mid Cobber. In terms of adding side visibility it does this in spades and it has fast become one of my go-to rear lights this winter, along with the aforementioned Magicshine SEEMEE300. Mounted up and switched on you really can see that, even if you’re coming perpendicular to the rider, you’re getting a full beam of light, rather than the faded edge of a central beam.

The mounting system is easy and relatively secure, and unlike many other lights I’ve tried the Knog Mid Cobber didn’t have a dependency to rotate around sideways on aero seatposts, something the SEEMEE300 suffers with quite badly. I also like the fact that the O-ring is replaceable, meaning that if it snaps then it isn’t curtains for the whole light. 

I also cannot fault the battery life, for the intended use case at least. This is firmly in the commuter light bracket for me, and so I don’t really think it’s fair to compare it to those lights that can keep on truckin’ through the night at higher intensities. It will get you to and from the office on a single charge on basically any of the light modes, and at the office, there should be enough USB ports kicking about for you to charge it up if you’re forgetful. 

Despite having 8 modes, which is more than I’d really like to have to cycle through, they are all distinct enough that you can easily find the one you prefer, something that can’t be said for the SEEMEE300 or the Lezyne Strip Drive Pro 400+. 

While the lighting and duration left very little to be desired, what did feel lacking for me was the build quality. Rear lights are often subjected to a lot of abuse, particularly if you don’t run mudguards, but it didn’t take long for the rubber bumper to peel off mine. It’s an easy fix with some superglue, but after only a few months of intermittent use, it isn’t great. I also am not particularly fond of having a male USB as the charging port. I understand the reasoning - no cables mean fewer places for water ingress - but over time I worry the connections would wear out if they get gritty. Given it has to be in the port a certain way up too it means that it depends on having a certain amount of free space around it to be inserted properly. 

Value

With an RRP of £62.99 / $69.95, the Knog Mid Cobber is quite a premium commuter-facing rear bike light, but it performs far better than your normal run-of-the-mill clip-on commuter lights. For this price I’d expect the build quality to be better though, so it’s not all sunshine and roses. 

Verdict

If you’re looking to set yourself up with the ultimate commuter bike light for the rear then I think this is probably it. It’s a little bit more of an outlay over properly bargain-basement options, but I absolutely felt safer and more visible with it attached to my bike than I did with most other options. It’s easy to install, has no cables to lose, and is only really let down by a slightly lacklustre build quality, and the existence of the Magicshine SEEMEE300 which also offers great side visibility at a slightly cheaper price, though the user interface there is far more confusing.