The Blinder ARC 640 is the brightest light that Knog offers. It produces a bright, broad beam with decent battery life in a compact and good-looking package.
Knog claims the light is fully waterproof and it coped well with some pretty foul conditions. One switch accesses all functions and it's easy to operate even in gloves, providing a positive click.
I was able to ride confidently in an unlit park with the light on full beam, but would want something a bit brighter if taking on some night-time trails or unlit country roads. The other modes were excellent for general commuting, and when using the flash function I was pretty sure no motorist would miss me.
A built-in plug enables the light to be charged straight from a USB port without cables, so theoretically all you need to carry around with you is the light itself. In reality, while this works well on a laptop, when the weight of the light is supported by your desk, you'll probably need to use the provided extension cable when charging from a PC.
In common with all Knog lights, the mount system is integrated, making it easy to swap between bikes and avoiding problems with losing important bits and pieces. Unfortunately the mount is probably the main weakness of the light. When strapped straight to my bar I found that it slipped a little after hitting bumps or potholes. Not a dramatic shift, but enough to possibly dazzle oncoming drivers.
Mounting the light to a bar-taped area stopped this from happening, but meant less room for my hands when riding on the tops. The straps can also be changed according to handlebar size and two sets are included for 25-30mm bars and 30-35mm bars.
The silicone straps lock into place using a small catch – a bit like that on a watch strap. This is secured by a small magnet. On a previous version that I tested, the magnet fell out and got lost, meaning the catch would not hold firm. So far on this light, the magnet has stayed put despite a fair bit of abuse. Replacement mount systems are available relatively cheaply, so if you really like the look of the light don't let that put you off.
A bright, good looking light that integrates everything you need, but the mount could be better
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road.cc test report
Make and model: Knog Blinder ARC 640
Size tested: n/a
Tell us what the light is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
Knog describes the Blinder ARC 640 as its top of the range light, aimed at serious road and trail riders. It belts out 640 lumens from a compact package with an integrated mount and USB recharger plug. It's certainly bright and gives a broad beam, although I would prefer something brighter on unlit roads.
Tell us some more about the technical aspects of the light?
LIGHT OUTPUT : 640 lumens
DIMENSIONS : 32 x 32 x 100.5mm
WEIGHT : 150g
LIGHT MODES : 4 light modes: High, Medium, Low & Flash
BIKE ATTACHMENT : 2x interchangeable straps for bars 25-30mm / 30-35mm in diameter. Helmet Mount included
BEAM ANGLE : Elliptical beam; 16° (vertical) x 24° (horizontal)
RUN TIMES: High beam 1.7 hours. Medium beam 3.3 hours. Low beam 7.3 hours. Flash 15 hours.
The body of the light is chunky, solid and well put together. It has survived intact despite being dropped quite a few times! The switch gives a positive click and can be operated when wearing gloves. The integrated silicone mounting straps can be changed according to handlebar size and two sets are included for 25-30mm bars and 30-35mm bars. They secure to the bike with a catch similar to a watch strap and are held in place with a small magnet. (More on this in the main review.) A helmet mount is also included in the package, but this is quite bulky.
There is a single switch to operate the light; a prolonged press is required to turn it on, reducing the chance of accidentally turning it on in your bag and running the battery down. A single press then circulates through the various modes. An LED light next to the switch indicates which mode you are in and warns you when battery life is getting low.
The built-in clamp does make swapping the light between bikes very easy, but it tended to slip when riding on rough ground when attached straight to the bar. This was solved by attaching the light to a taped area.
No problems despite being used in some pretty horrible conditions.
Recharges quickly and lasts well, especially on flashing mode. The built-in plug can be slotted straight into a USB port, great if you're using a laptop, but it tends to fall out if its weight isn't supported. A short extension cable is provided and gets over this.
On full beam the light is very bright with a good, broad beam. I used it when cyclo-cross training in an unlit park and felt confident riding fairly quickly. On unlit roads I would want something a little brighter, though. Commuting on flashing mode, there's no way drivers could miss you...
No problems so far. The mounting system may be potentially vulnerable.
Quite a chunky light and fairly heavy. Only really noticeable when using the helmet mount.
Tell us how the light performed overall when used for its designed purpose
Great as a bright commuting light but you might want something brighter for serious road and trail riding.
Tell us what you particularly liked about the light
Looks great. Nice to have everything included in one package.
Tell us what you particularly disliked about the light
The mounting system was not really secure enough for riding on rough ground when mounted directly to the handlebar.
Did you enjoy using the light? Yes
Would you consider buying the light? Maybe
Would you recommend the light to a friend? Yes
Use this box to explain your score
If the mount was a bit more secure this would score 7; it's good, especially for commuting on lit roads, with some off-road capability, but it's not one for serious riding on unlit roads. It's also a little overpriced.
About the tester
I usually ride: Genesis Day One Singlespeed My best bike is: Souped-up Cannondale CAADX
I've been riding for: 10-20 years I ride: A few times a week I would class myself as: Experienced
I regularly do the following types of riding: cyclo-cross, commuting, club rides, fixed/singlespeed, mountain biking
Andy Ward works his socks off for the NHS as a GP and teaching at Leicester Medical School. After a brief foray into road racing he decided it hurt less to fall off on mud and is now most likely to be found on his cyclocross bike. He recently surprised himself by completing the Three Peaks without breaking his bike or any limbs