Buyers’ guide to bike lights


Bike lights are an essential kit for every rider during the hours of darkness. Picture: iStock

With winter fast approaching and the days getting shorter, a quality set of bike lights is a crucial part of every cyclist’s kit. For commuters, a basic set of lights that will allow you to be seen by other roads is are paramount for safety and required by law. Road riders who wish to continue their training regime in the evening or early morning will also benefit from lights that offer enough power to illuminate unlit back roads (without being so bright as to endanger other road users). Meanwhile, for mountain bikers, there is a huge range of powerful lights on the market that opens up the tantalizing possibility of night-time trail riding, enabling you to keep up evening rides right through the colder months (and being a whole lot of fun, besides).

The right set of lights for you will depend on the type of riding you wish to do and where you will be riding, and options are available to suit all budgets. With modern lights offering a huge range of feature variations -power, bulb type, beam pattern, battery type and more – it’s important to do your research before you take the plunge. Read on for an in-depth guide to the types of lights that are targeted at different riding situations, and an explanation as to the major features on offer.

The big question – to see or be seen?

When considering the type of bike lights you want to buy there is one main question to be answered – do you want to be seen (by other road users) or do you want to see (illuminate the road or trail on front of you so you know where you are going)? If it’s a case of just letting other road users know you are there, a basic set of front and rear lights will do the job. But if you want to cast a beam on the way ahead, there’s a lot more to take into consideration and you will need a light – specifically a front light – that’s up to the job.

In broad terms, there are three main usage scenarios for bike lights and three corresponding categories of lights.

Commuter: For commuters or leisure riders riding in a lit urban environment during the hours of darkness, the primary concern is that they be seen by other road users. For this purpose a basic set of front (white) and rear (red) lights are adequate, and in the UK and Ireland, it is required by law. Lights of this type can be basic in construction and design and available at an entry-level price point, but even so, there are a couple of key features to look out for. Because other road users may be approaching you at an angle, look for lights that offer good side-on visibility – a narrow, focused beam may be visible to road users approaching from straight on, but when emerging from a junction you will need to be seen from the side. The vast majority of both front and rear commuter lights also feature a ‘flashing’ or ‘pulse’ mode, which can be helpful to enable drivers to distinguish you from fixed lights (e.g. street lamps) and which also improve battery run times.

“I could talk about this for hours,” laughs explains Jemma Nimick of Belfast-based company See.Sense, makers of the ICON+ series of ‘smart’ bike lights.

“There are lights that are designed to guide your path and lights that let you be seen by other road users – all our lights are designed to be seen. A key thing in this is side visibility, so our lights have 270-degree visibility and use top-quality Cree LEDs which are also visible in daylight. We’d actually advise that riders use their lights at all times, night and day – ideally all year round but especially in the winter months.”

Road riding: For road riding in the winter months outside of an urban environment, you are going to need a front light that is not just visible to other road users but which is capable of casting a beam onto the road ahead so you can see where you are going. The power and pattern of that beam will depend on the type of lights (we’ll discuss this more below), but the principle is that you need to step up from a light which shows others you are there, to one which you can navigate by on unlit roads. If you intend to continue your training regime at night you’ll need a beam that casts far enough into the distance to allow you to travel safely at speed, but you’ll also need to be mindful that an over-powerful setup runs the risk of dazzling oncoming road users.

Off-road: For off-road riding at night, often negotiating tight singletrack at pace, you’ll need the most powerful setup of the three – a bright, focused front light that is capable not only of throwing a beam a significant distance down the trail but which also offers a wide beam pattern so that you can see obstacles in your peripheral vision. Many MTBers also combine a fixed-position front light (mounted on the handlebars) with a second lamp mounted on their helmet. On twisty trails, a fixed light may often end up not pointing directly ahead, so a helmet light is a great option to make sure you can always direct a beam where you need to.

The evolution of bike lights

Bike light technology has evolved considerably in recent years, and we’ve come a long way from dynamo-powered lamps. The biggest changes have come with regard to bulb and battery type, with new innovations giving us more powerful lights in smaller, lighter and longer-lasting packages, and available at lower and lower price points. Basic bike lights of old used halogen bulbs and disposable alkaline batteries – cheap and easy to pick up, but the bulbs were weak in comparison to modern LEDs and burned out faster. You’ll still find some bike lights of this type available at the cheapest end of the market, but it’s worth the small extra spend to take advantage of giant leaps in power, durability, and user-friendliness. For riders looking for a powerful, high-performance light setup their options were limited to HID (High-Intensity Discharge) bulbs paired with rechargeable Ni-Mh (Nickel-Metal Hydride) batteries. These offered great lighting power but at a cost – HID bulbs were fragile and expensive to replace, while Ni-Mh batteries were bulky, heavy and temperamental if not recharged correctly. Bike lights of this type were popular for off-road riding but the size of the battery meant they typically had to be mounted to the frame separately and connected to the front lamp by wires, which was a bit of a faff.

The last few years have seen both basic and performance lights of this type superseded by a new generation of lights using tiny-but-powerful LED (light-emitting diode) bulbs and rechargeable Li-Ion (Lithium Ion) or Li-Po (Lithium Polymer) batteries. Similar to the types of batteries used in smartphones and tablets, Li-Ion batteries are smaller, lighter and hold a charge better than their Ni-Mh predecessors. Modern lights also typically feature USB charging ports for ease of use – smaller units may plug directly into your laptop to get a charge, while more powerful lamps can be charged via a mains adaptor. Again, as technology evolves the constituent parts become smaller, lighter and more affordable, and now even the majority of powerful lights intended for off-roading come as an all-in-one lamp/battery package light enough to be mounted on your bars or helmet (rather than a separate lamp/battery setup).

Key features – and what to look for

Once you have considered how you will use your bike lights – see or be seen, remember? – and have a budget in mind, its time to start browsing. Light manufacturers will advertise their products as having a number of key features, the most important of which we’ll discuss below.

Bulb type

As above, the older type of halogen or HID bulbs have largely been replaced by LEDs. The number and type of LEDs used in a lamp are a determining factor in a light’s power, but not the only one – power/brightness is also affected by the lamp optics (the lens and reflectors, which control the focus and spread of light), beam pattern, light mode (flashing or steady-state), battery power and even the volume of charge in the battery. Some units may ‘peak’ in power at a particular stage of the charge cycle – taking a little bit of time to warm up when first turned on, emitting full power for a portion of the burn time and then gradually declining in power as their charge runs down.


The power output of a lamp is expressed in Lumens, which is the standard international unit used to measure power from a light source. Very basic front/rear lights for visibility only will be as little as 20-30 lumens (these may also be called ‘safety lights’), while ‘decent’ commuter lights will be in or around the 100-lumen range. For lights that are capable of throwing a beam onto the road ahead, you’ll need at least 200 lumens (and ideally something closer to 500), while off-road lights can be as powerful as 1,000 or even 2,000 lumens.

However, it’s worth noting that ‘power’ of light as expressed by the manufacturer in lumens also needs to be taken with a pinch of salt. In real-world riding conditions, the actual power can be a bit lower once the current has gone through all of the circuitry, bulb and lens/reflectors, and we haven’t even begun to talk about beam pattern yet and how this can affect the brightness of a light in action (we will below).

So while lumens are the go-to measurement for manufacturers who want to advertise how bright their lights are, another measurement called lux (lumens per square meter) is also useful to be aware of. Lux measures not just the power output from the source of the light, but the strength of that light when it is shone on a surface in the distance. A light with a focused beam pattern will have a higher lux than a light with a broad beam pattern, for the same rate of lumens… but a light with a broad beam pattern will have more coverage so your peripheral vision will be better.

Beam pattern

Ok, now we can talk about beam pattern.

Beam pattern is determined by the lamp’s optical elements (lens and reflectors) and falls in a range between focused and broad. There are advantages and disadvantages to each – a focused beam will throw a sharp spot of light a greater distance, illuminating a smaller area but allowing you to see further. A broad beam will throw a wider ‘cone’ of light – given greater coverage but shorter distance. A focused beam will enable you to see farther down the road at the expense of peripheral awareness. A broad beam won’t let you see in the distance but will give you a more ‘rounded’ view of what’s ahead.

Again, the type that is right for you depends on your riding conditions. For fast road riding at night, you may want a focused beam to alert you to upcoming potholes, while trail riders might want a better general picture of the twists and turns ahead. Most manufacturers try to strike a balance between the two types – or some riders may find that running two lights with complementary beam types (e.g. a bar light with a broad beam and a helmet light with a focused beam) gives them the best of both worlds. A final thing to consider, especially for road riders, is beam direction. Ideally you want the beam to be pointing ahead and slightly downwards, lighting up the oncoming road but low enough to avoid dazzling oncoming cars, and avoiding any wasted illumination (by pointing up into the sky). Most lights will enable you to adjust the lamp mount/bar clamp to amend the beam direction, but it’s something to be aware of if using a fixed position (e.g. a lamp compatible with a Garmin or GoPro mount).

Beam temperature

Not quite as crucial as beam pattern, but beam temperature is worth mentioning. This is a measure of the ‘color’ of the beam, ranging from harsh white/blue (offering lots of detail and contrast but greater potential for glare) to warmer yellow/red tones that reduce the potential for ‘bounce-back’.

Battery type/power/run time

As we mentioned earlier, disposable alkaline batteries are now only used on the most entry- of entry-level lights and bulky Ni-Mh units have largely been filed away under ‘obsolete’. The majority of modern bike lights use compact, USB-rechargeable Li-Ion or Li-Po power units, much the same as you will find in your phone, tablet or laptop (in fact, some new bike lights on the market double up as emergency power packs for your smartphone, which is a neat idea).

With batteries, the crucial thing is run time, which can vary dramatically from light to light and depends to a large extent on how it will be used. Smaller commuter lights don’t require as much juice as more powerful units, so the batteries in the latter are likely to be larger and higher-capacity (and in the case of off-road lights, more likely to be mounted via a separate battery pack, although the range of all-in-one units continues to increase).

NOTE: Battery capacity is measured in Milliamp-hours or Amp Hours (mAh or Ah), although typically only higher-end lights will feature an mAh value in their spec list. Manufacturers will usually offer estimated run times, which again need to be taken with a pinch of salt. If you want to check or calculate your own light’s theoretical run time you can divide the given battery capacity value by the amperage at which the light operates, should that be your thing?

Whatever your battery capacity, how it is used will have a significant effect on run time. Many mid- to high-end lights will allow you to select between modes e.g. low, medium, high (full power) or flashing – full power will drain the battery quicker (run time of 1-2 hours), and flashing will give you the longest run time (up to 25 hours, depending on battery capacity). It can be useful to consider conserving your battery’s energy on long rides – flashing mode for city streets, low/medium power for long climbs and then high power for fast descents or riding at speed. Cleverly managing how much power your light uses will help you to maximize run time (some new lights with smart functionality may even do this for you, automating the light output according to conditions).

Battery capacity will also decline with age and in cold weather. To avoid running out of juice mid-ride it’s worth looking for a light with some means of indicating when battery is running low, e.g. a small LED which flashes green/orange/red according to the volume of charge, or emits an audible alert when the needle is close to E. For long rides away from civilization it’s also worth carrying a smaller, less expensive backup light in your trail pack or jersey pocket – that way if your main lamp runs flat or fails you’ll at least have enough light to find your way home.

Mounting and fit

As well as the power and functionality of the light unit itself, you also need to take into account how it is mounted to your bike. Lower-end front lights and rear lights will generally mount to the bars or seat post with a simple elastic O-ring or rubber/Velcro strap, which takes a matter of seconds to slip on or off. This is fine for small, lightweight units and city use, but for riding on rougher roads and especially off-road (where the lamp is likely to be a little heavier anyway) you’ll need a more secure clamp mechanism, or else the rattling and jolting of your bike will cause your lamp to loosen and tilt.

Most manufacturers will have their own proprietary designs but there are some which are compatible with existing mount standards from the likes of Garmin or GoPro, meaning you can just lock your light into your GPS mount or helmet camera mount. Whatever type of mount is used, look for something that doesn’t need any tools to operate and which can be removed by freezing, numb fingers. You’ll thank us later.

For the most part, light mounts are designed to fit with round, standard-diameter (31.8mm) bars and seat posts – if using aero bars or posts you may find it a bit more challenging to get the mount to sit correctly, so it might be worth looking for an aero-specific design (yes, they are out there).

Weather protection

Because lights are more likely to be used in the winter they may be exposed to the elements, so some level of waterproofing is advantageous – a robust, non-corroding housing and proper sealing of all cables/switches, etc. Look for a light with an Ingress Protection (IP) rating of at least IP64, which means it is sealed from spray getting in (an IP67 rating, in comparison, means it’s completely waterproof up to 1m in depth).

Smart functionality

Finally, there has emerged a new breed of lights that not only offer powerful illumination, lightweight and long run times etc. but are also pushing the boat out in terms of additional tech and smart functionality. Combination light/onboard camera units are becoming more common, while the Varia series of lights from Garmin throws some interesting tech into the mix. The Varia Radar rear light, for example, works with Garmin computers to warn riders of vehicles approaching from behind, while the Varia front light has the ability to automatically adjust beam reach and direction according to speed.  Irish company See.Sense is also innovating with their ICON+ range of smart bike lights, which automatically reacts to changing road conditions (e.g. flashing brighter when approaching a junction or roundabout), which can be paired with a smartphone app for lots of configuration options, and which double up as a data collector gathering a host of information about routes, roads, cities and riders.

“A lot of lights are getting a bit smarter these days,” explains Jemma Nimick, “but our lights have always been built with this functionality in mind. They contain a number of sensors including an accelerometer which can tell when you are speeding up or slowing down – such as when approaching a junction – and which can then adjust the brightness and light pattern accordingly.

“Because you can connect our lights to your phone via Bluetooth, you can turn also down the brightness to get longer run time, or even dim your lights when riding in a group so you don’t dazzle your riding mates behind you!”

The bottom line

If you’re going to ride between the hours of sunset and sunrise a set of front and rear bike lights is a must. For safety and visibility to other road users, a range of options are available at the lower end of the price scale but look for something that makes you stand out to other road users as much as possible. For riding on unlit roads, and for nocturnal MTB adventures, you’ll need something a lot more powerful, capable of lighting the road or trail ahead and with enough capacity to see you safely home. Whatever lights you go for, embrace the darkness and enjoy the pleasure of a night-time spin!


Leave A Reply