Buyer's guide to mountain bike lights

By Guy Kesteven, What Mountain Bike & MBUK | Wednesday, October 20, 2010 7.00am

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 2,600 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 at 5 metres 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.

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

Key lighting components, and what to watch out for

LEDs

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. Technological advances mean performance has leapt forward in the past few years and each new season brings significant upgrades.

Prices are dropping too, so you’ll generally be forking out significantly less for equivalent performance compared to last year’s lights. Different LED groupings, lenses and outputs can give very different performance though, so buy a light to suit your biking.

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.

Optics

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. 

Throwing more light down the trail generally lets you see more detail earlier, and therefore ride faster. But once you’re on the trail you’ll soon adapt to whatever lighting you’ve got and, from experience, faster riders in a group will still be faster whatever lights they’re using, so don’t get hung up on output. Bear in mind that you get better all-round illumination, depth perception and trail awareness from a less powerful head-mounted spotlight and wide bar-mount combo than a single, more powerful light.

Reliability

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. The great news is that most lights available now are reassuringly reliable.

If something does go wrong though, a well-established company is generally a lot easier and quicker to deal with than a foreign internet seller, which is why we’ve only included properly UK represented lights in this test

Mount/bracket

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.

If you are thinking of using a helmet mounted light, you need a lamp that’s light enough to be comfortable and secure on your lid, rather than a neck snapper. You’ll need an extension cable and helmet mount too, so check if that’s included or an optional extra.

Battery

Like LEDs, lighter, tougher, far more random charge resistant Lithium Ion (Li-Ion) chargeable batteries have revolutionised mountain bike lighting compared to older lead acid and NiMH batteries. Battery and lamp efficiencies still vary dramatically, so don’t judge run times just by size and/or Ah (ampere-hours) capacity but by our tested and verified run times.

The longer you ride, the more battery run time you'll need. Being able to run full power on descents or stop to fix a mechanical without worrying about getting stuck in the dark is vital. Sub-zero temperature can also sap battery life dramatically so buy a bigger battery if you like proper winter epics.

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. Check whether the battery will fit your bike – it isn’t always the case with curvy alloy or fat carbon frames.

Switch

Being able to check remaining run time is often nearly as important as actual battery life. The switch not only turns the light on, but also lets you change power output levels. It needs to be easy to operate while riding, even with gloves on, but hard to operate accidentally. Many lights now use backlit switches which double as mode and/or run time indicators using traffic-light-style colour changes.

Charger

The most easily forgotten part of the lights package. Chargers range from USB leads to a plug with a lead on that lights up green when it’s done, to LCD-screened smart chargers or even battery docking stations that let you change lighting options via your PC. Car chargers are great for 24-hour races.

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. This can be important if you’re the sort of rider who forgets their battery is flat until an hour before a ride.

Leads

There are increasing numbers of all-in-one light systems, but most sets still use a head unit attached to the battery by a lead. Leads are 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 and are long enough to fit your bike. Every joint wastes power, so it makes sense to keep things simple.

Separate lights or all-in-one units?

Several other manufactures are now following UK pioneers Exposure down the all-in-one route rather than using a separate battery and light. Mounting is easier and the whole setup much tidier, but larger capacity all-in-one lights aren’t helmet-compatible. They’re also less upgradeable in the long-term than the most versatile modular systems such as those offered by Lumicycle.

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

Jargon Buster

  • AMP Hour - A measurement of battery capacity. The bigger the capacity, the longer your lights will run. You need to divide this value by the amperage the light operates at in order to get the theoretical run time.
  • Bag - A cloth pack that holds the battery onto the bike's frame.
  • Bar mount - Light bracket that fits around oversize (31.8mm) and/or older 1in (25.4mm) diameter handlebars.
  • Battery cell - The single units that wire together to create a battery pack.
  • Bottle - Plastic water bottle converted to hold a large capacity battery.
  • Candlepower - Unit of light measurement.
  • Cell - Individual unit within a larger battery block. Most mountain bike light batteries are twin or quad cell units.
  • Colour temperature - Colour of the light. The more blue-white, the ‘colder’ the colour, the more yellow, the ‘warmer'
  • Cree - Leading LED manufacturer.
  • Flood - Head unit designed specifically tospread light over a wide area.
  • Halo - A distinctive ring in the pattern ofthe beam.
  • Halogen - Best of the conventional bulb types. Cheap and easy to replace, but power-hungry so needs big, heavy batteries. Most manufacturers now use LEDs instead.
  • Helmet mount - Bracket that lets you fit the light on your lid.
  • HID - High Intensity Discharge. A metal halide lamp that uses a tiny but extremely bright striplight bulb that only draws 10W but produces more light than a 40W halogen bulb. Gives that distinctive blue/white alien light of BMW headlamps. Most manufacturers now use LEDs instead.
  • Jack - Connector plug on the lead.
  • LED - Light Emitting Diode. A solid state semi-conductor that glows brightly when a current is passed through it. The 'bulb' choice of most manufacturers.
  • Lead - Cable that connects the head unit and battery. Extra long extension units are available for use with helmet mounts.
  • Lens - The screen over the LED and reflector that protects them and can also be used to modify the beam.
  • Life indicator - Traffic light style colour change display that indicates the remaining charge in a battery.
  • Li-ion - Lithium Ion. The most expensive but lightest, most efficient battery available. Also the easiest to look after in terms of charging/ recharging and therefore a very good thing.
  • Lumen - Often quoted measure of the theoretical power of a light. Thermal issues and management circuitry normally make it an optimistic guide at best, though. With no standard way to measure it for bike lights, most figures can't be usefully compared.
  • Lux - Lumens per square metre. The real light output figure that we generally use in our comparative lab tests.
  • NIMH - Nickel metal hydride. Cheaper battery type that's reasonably robust in a charge/recharge sense but heavier and bulkier than a Li-Ion for the same capacity.
  • O-ring - Thick rubber band used in some handlebar mounts.
  • QR - Quick release mechanism.
  • Reach - The distance down the trail that the light illuminates.
  • Reflector - The shaped reflective surface behind the LED that concentrates and reflects the beam of light.
  • Seoul - LED manufacturer.
  • Smart charger - Charger that senses how full/ empty the battery is and adjusts its efforts accordingly rather than burning down your house.
  • Spot - Head unit designed to focus light in a narrow, long reaching beam.
  • Throw - How far a light's beam can reach in front of it.
  • Voltage - The power level the battery releases its energy at.
  • Watt - A measurement of power. You'll often see bike light outputs quoted as 'equivalent to a 20W halogen bulb' for example.

How we test mountain bike lights

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:

Related links

Light output is calculated using a lux calibrated industrial light meter

Latest lights on test (September 2011)

We've just finished our latest round of light testing. To view the results, including beam shots, check out our feature, Best mountain bike lights.

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