Buyer’s guide to mountain bike lights

A winter of dark nights and a summer of 24-hour racing means good lights are essential. but the trail light market is diverse and potentially confusing. Here’s what you need to know to make sense of it all and pick your perfect match.

How bright is right?

With some bike lights now kicking out a claimed 2,000 lumens, night riding has never been a brighter experience. This means we can ride technical trails faster than ever. In terms of what detail you can pick out, though, this level of lighting still doesn’t turn night into day.

That’s because even with a bar and helmet light you’re only lighting the trail with two light sources rather than all-round light saturation, and you’re only seeing a very small part of the picture rather than the whole trail in its landscape context. Different colour ranges also makes it hard to pick out surface texture and detail that’s vital for assessing grip.

In some damp wooded or misty/foggy situations, more light can actually cause more bounced back glare than lower powered lights. the most powerful lights are often overkill anyway, because you can’t focus that far away. they are useful, however, if you’re riding in front of someone who has a bright light that would otherwise leave you riding in your own shadow.

As a rough rule, anything under 100 lux means you’ll be stumbling along fairly slowly on all but the smoothest trails. a focused 150 lux output is enough for a useful helmet light, but a bar mounted flood will be low on reach. 200 lux is enough for confident riding at middle ring speeds on most trails, while 300 lux plus means you can properly push the pace pretty much everywhere.

If you’re wondering why we’re using lux readings rather than the lumen or candlepower figures normally quoted, it’s because they’re more practically relevant than figures based purely on power. more on that in the science bit below.

Name brands vs internet deals

For as long as we can remember, riders have been tinkering with piles of bits from an electronics catalogue to create their own light setups. while the results can be impressive in output terms, their reliability and level of finishing can be very poor.

Should anything go wrong you’re also dealing with an enthusiastic amateur at best rather than a proper company with readily available spares, sorted customer service plus insurance if something goes really wrong.

The global reach of the internet means you can also buy bargain lights direct from the Far East. from our experience, initial performance fades pretty fast and with no formal backup, you’d best be handy with a soldering iron or prepared to throw them away and buy a new set (or at least a new battery) after a season of use.

Our testers go out in all weathers to test the latest lights to their limits:

Invest in a decent set of lights and you can continue riding throughout the winter


Most lights now use LEDs (Light Emitting Diodes), as they produce more light for less power than a conventional bulb and are far less fragile than HID lamps. LED technology is advancing at a crazy rate with more powerful and efficient LEDs meaning some lights have gained 30 percent power since last year for the same battery draw.

Lamp body

The lamp body (or head unit) houses the LEDs, optics and the electronic circuitry to control them. its design is crucial in reducing overheating and the overall weight and size of the light.


The combination of lens (in front of the light source) and reflector (behind it) controls the spread, depth and consistency of illumination. Narrow ‘spot’ beams are great for long-range vision at high speeds or helmet-mounted use, but not so good in tight singletrack. Broader ‘flood’ beams add context and ‘where next’ light coverage at the expense of depth.


Mixing delicate electronics, high operating temperatures, powerful batteries, mud, rain and regular crashes isn’t easy. Yet reliability is absolutely vital, as light failure at speed on technical terrain is no joke.


A great lamp is no use if you can’t fit it to your bar (or helmet) or it just wobbles and points the wrong way when you do. a weak or loose bracket that suddenly twists or shakes loose on a rocky descent is a recipe for disaster, and a badly placed helmet light will drag your lid down or wring your neck.

Make sure you can position the light where you want it, and that it’ll do the job. Check that bigger lights will actually fit on the curve of your handlebar without sitting at a crazy angle. Most mounts use clips and spacers but O-rings are a great simple solution.


Battery performance has made massive leaps recently, with most lights now using light, long lasting and easy to charge Lithium Ion (Li-Ion) batteries. the quality and capacity of battery (rated in mAh/milliampere hours) and the power draw of the lamp are what govern max power run times.

the longer you ride, the more battery run time you’ll need. Most brands sell extra batteries (often at a discount if bought with the light) so you can always swap halfway. Check your batteries are properly prepared for maximum performance (this should be in the instructions) and take a back-up until you know you can rely on their run times.

Some lights mount their battery in a simple bag with a Velcro strap which can work okay, but can also slide about and scratch paintwork. Batteries in a converted water bottle are great if you need a big capacity cell. Integrated batteries are neat, but some of the big ones are very bulky on the bars.


Most chargers now use smart circuits for a fast initial charge that slows to a trickle so they don’t damage the battery, but actual charging speeds can vary quite dramatically. Car chargers are great for 24-hour races.


Often overlooked but vital to overall reliability. you want secure connectors that don’t fall out and joining sections that won’t let water or muck in. every joint wastes power though, so it makes sense to keep things simple.

Our testers go out in all weathers to test the latest lights to their limits:

Pair a helmet spot with a bar-mounted flood and you’ll generally have the best of both worlds

Being stuck on a wet winter’s night, miles from anywhere with a failed light or everything suddenly going pitch black halfway down a technical descent is a really serious matter. That’s why we take our lights testing extremely seriously.

For all the calibrated data on max power run times, lux ratings, light spreads and ranges we can get in the workshop, what really matters is the test feedback we get on the trails: which brackets continually loosen or which leads fall out; which batteries bounce about, scratch paint or are a right pain to fit on different bikes; which drown in downpours.

There’s no substitute for time on trail in all weathers to find out this crucial stuff and we’re not talking about the past few months with these lights either. We also reference the sets we’ve run continually since last year to get in-depth, long-term, worst case use feedback that’s directly relevant to the riding you do.

Product reviewer guy kesteven tests run times and cooling:

We test lights out on the trail and in the workshop, and any failings soon show up

The science side

As is often the case with mountain biking, the scientific part of the testing is the easiest bit. Lights (lamp body plus handlebar bracket) and batteries are weighed on our scales.

We then measure the useful maximum power run time (to when the output fades and low battery warning lights come on) with pre-conditioned (used and recharged) batteries in the highest power setting on an aircooled rig to mimic the cooling effect of riding at night. We also measure the maximum casing heat of the lights with a thermal probe to see if any get dangerously hot.

Light output is calculated using a lux (a measurement of one lumen per square metre) calibrated industrial light meter placed 5m from the lamp in a blacked out workshop. (If the light has more than one beam or head unit we measure both separately and their combined output.)

This method does favour spot beams over flood beams but it’s still a more trail translatable measurement than the lumen potential of LEDs. the coverage, density and other specific characteristics of the beam are often more important than the peak brightness though, so we also take beam photos to make it easier to compare the lights.

The practical side

It’s the feedback we get from real world usage that really sorts out often very similar lamps in terms of trail performance. the reason I get to do lights testing up North most years isn’t because I’m a modern Edison, it’s because our local test crew put in more hardcore nocturnal hours on their bikes than any other group I know.

We’re talking serious sorties often two or three times a week all year round in every trail condition imaginable. Baked hard river bed runs that’ll shake a poor bracket or fragile circuit board apart in seconds or leave a badly bagged battery hanging by its lead; sub-zero tundra trudges that freeze a battery to horribly low maximum power run times; drownings in downpours and hip-deep bog crashes.

Most of the lights here have seen it all and, if the most recent versions have only been hammered through summer, we’ve certainly put the models preceding them through the most testing ride schedule possible. Repeated group riding, bike switching, recharging and battery flattening gives us the perfect comparative testing cluster too, so any failures or fading is immediately obvious rather than going unnoticed in isolation.

In other words, if a light scores well in this test, you know it’s gone through some proper optical and electrical purgatory to prove itself. for that reason, for our latest round of lights testing (see below) we’ve deliberately stuck with established (at least a year old) lights manufacturers to ensure anything we recommend is a fully supported product.

Light output is calculated using a lux calibrated industrial light meter placed 5m from the lamp in a blacked out workshop:

Light output is calculated using a lux calibrated industrial light meter

We’ve just finished our latest round of light testing. To view the results, including beam shots, check out our feature, Tested: 30 high-power mountain bike lights.

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Buyer’s guide to mountain bike lights

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