Thanks to continuing advances in LED and lithium battery technology, it's now not uncommon to see mountain bike headlights putting out 3,000 lumens or more. Most of these high-intensity lights incorporate two or three bulbs, however, requiring a separate battery pack to power them. With this in mind, we were intrigued when we heard that Light & Motion had declared its self-contained new Urban 850 Trail FC to be "the most powerful single-LED bike light that exists." We gave it a try and liked what it has to offer ... even if its claim may be a little hard to substantiate.

As its name implies, the Urban 850 Trail puts out a maximum of 850 lumens via a single CREE LED and custom firmware. While that's significantly below the output of some of the ridiculously-powerful multi-LED lights, we found it to be more than sufficient for our nocturnal trail rides.

A quick Googling, however, will show that a number of other manufacturers are offering single-bulb headlights that are rated as high or even higher – Cygolite's Expilion 850 reportedly also pumps out 850 lumens, while Australian start-up Indigo Lighting claims that its Indigo5 manages a whopping 1,800 lumens.

When we asked a Light & Motion rep about this, they responded that unlike the lights of some competitors, the Urban 850 Trail's output has actually been certified to the commonly-accepted FL-1 Standard. For their part, Cygolite and Indigo told us that their lights also measure up on the FL-1 system – the Indigo5 can only manage its maximum 1,800-lumen output for 30 minutes on its standard battery, although higher-capacity "booster" batteries are also available.

So suffice to say ... the Urban 850 Trail might not necessarily be the single brightest single-LED bike headlight in existence, but it's certainly among them, particularly if you stick to established brand names.

Putting it to the test

The headlight's built-in lithium-ion battery charges in 2.5 hours via USB, and is claimed to provide 1.5 hours of run time at maximum output. In our tests, although we started getting a low-battery warning at the 1.5-hour mark, the light itself kept going for just over two hours. Battery life can be extended considerably by selecting medium- or low-output settings (375 or 185 lumens, respectively), although if you're using it for honest-to-goodness mountain biking, you'll likely find those to be insufficient once the night truly settles in.

We were initially wondering if its single-bulb beam might be too narrow, but that definitely didn't turn out to be the case – the reflector provides 180 degrees of visibility, which nicely illuminated the sides of the trail while still not creating an overly-intense spotlight in the middle.

Using its silicone strap and mounting bracket, the Urban 850 Trail stayed securely in place on the handlebars, even after bumping over some rooty sections. The headlight can be panned to either side relative to the mount, allowing users to fine-tune where it's pointing. Although it did occur to us that this feature might let it jiggle out of alignment, that never happened. It could be more of an issue if using the light on your helmet (a mount is included), as it would be more likely to get hit by overhanging branches up there.

Some of its other features include IP67 waterproofing (immersible to 1 meter/3.3 ft for 30 minutes), a low-output "pulse" setting for increased visibility in traffic, and a total weight of 121 g (4.3 oz). It's priced at US$179.

We definitely liked the Urban 850 Trail FC, and appreciated the fact that it was considerably smaller and sleeker than more needlessly-intense multi-LED lights that require separate battery packs. That said, it would be nice to have the options of either forking out for a higher-capacity onboard battery, or plugging the light into an external battery – even at two hours, some riders may find that it just doesn't deliver its 850 lumens for long enough.

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