The best bike light for you depends a lot on where you’re riding. A bike light that works fine for short trips around town won’t be the best option if you’re riding longer distances at night on unlit roads.
All-round visibility is important too as most accidents involving bikes are the SMIDSY type (sorry mate I didn’t see you) where a driver turns into you. The best bike lights will have a design that shines light to the sides, not just forward and backward. The designs of the best front bike lights will be different to the best rear bike lights too, as the needs for illumination are different.
Almost all bike lights now use LED lights. They’re very efficient and can run for hours, although some high powered lights may get hot, particularly if you’re not moving. They’re usually powered by USB rechargeable lithium ion batteries that give long run times and reasonably quick charging.
Many will use a standard micro-USB charging cable, some like the Lezyne Hecto Drive has built in USB plugs, while others, like some of Exposure's units, need their own specific USB cable.
The best front bike lights: what to look for
A light’s peak output is usually measured in lumens, although you’ll sometimes see lux numbers quoted instead. In general, if you’re riding in town you want a light that helps you to be seen, whereas if you want to ride reasonably fast on unlit roads, you’ll want a light that lets you see where you’re going effectively.
The cut-off between “be seen” and “see by” lights is normally considered to be around 500 lumens output, although you’ll probably be able to see reasonably well with a lower output once your eyes adjust to the dark and if you’re not dazzled by other traffic. Lights for off-road use need to be brighter still so you can spot obstacles and may have over 1000 lumens peak output.
You also need to consider how long the light will work for before the battery goes flat. Makers will normally have figures on their sites for how long a light will run for in different modes.
You can up your battery life considerably by selecting a lower output level, while flashing modes use less power than constant ones. Most lights will have at least two constant and two flashing modes and they’re usually arranged so that you can cycle through them by pressing the on/off switch.
Some lights have a pulsed mode too, where the light intensity varies but the light is always on, while others will have a “random” flash mode, that should up your visibility.
In some lights, you need to cycle through having the light switched off when you change modes, which isn’t ideal. But the best bike lights will let you cycle through the different modes without the light going dark, with a longer push needed to switch on and off. You can also find lights with a locked setting that stops them switching on in a bag, so you don’t get your light out to find that the battery has gone flat.
Programmability is a useful feature you’ll find on some lights, which lets you select how many modes you have and how intense each is, to match your riding style. It’s found on many of Exposure’s pricier lights.
If you’re expecting to ride for a really long time, you can find lights which you can plug into an external power bank. Dynamo lights powered by your wheels are also an option, although if you opt for a hub dynamo it starts to get expensive as you’ll need a new front wheel. Modern dynamos include a battery so that the lights don’t go out when you stop moving.
You can find additional safety features too, like Beryl’s laser lights which project a bicycle symbol ahead of you as you ride.
The best rear bike lights: what to look for
Since they’re just to be seen, rear bike lights don’t need such high output as front lights. That means that they are usually more compact and a bit cheaper than a “see by” front light.
The best bike rear lights will be designed for wide angles of visibility, so that vehicles approaching from an angle can see you better. They’re also likely to have a range of flashing or pulsed modes as well as constant, with higher intensity flashing modes designed for daytime use, alongside less bright options for longer runtimes when riding at night.
Some rear bike lights have additional safety features. The Beryl Burner Brake light is one of several options that detects when you slow down and flashes brighter. Meanwhile, the Lezyne Laser Drive projects a pair of orange lines behind your bike to help stop close passes, while the Garmin Varia rear light has a built-in radar. This detects approaching vehicles and switches the light to flash brighter as they get close. It also alerts you to the vehicle’s approach via an audible beep and a schematic on a Garmin computer.
All bike lights need to be designed to be waterproof and dustproof and most will be rated IP6 which means they can survive a prolonged soaking. It’s particularly important for a rear light that, if you don’t have mudguards, is likely to be sprayed with damp and muck from your rear wheel. You want a design that’s reasonably easy to clean up too.
A good mounting system is important, particularly for heavier front lights, where a light can bounce around on a less substantial mount, leading to an irritating flicker. The best front bike lights with a larger format will use a screw on mount rather than the rubber strap options more common on smaller front lights and most rear lights.
Any mounting option needs to let you detach the light itself quickly though, so you don’t have to spend too long fiddling around at the start and end of your ride.
You can also find wearable lights, which you can attach to your clothing or a bag. It’s a useful option, particularly for rear lights, that makes your lights more portable.
Some lights come with a helmet mount that screws into the vents in your helmet. These may have a front beam only or include a front and a rear light. With the light high up, they’re a good option for urban riding. Paired with a bar mounted light, a higher powered helmet light works well for unlit roads and off-road rides too, but be careful not to dazzle oncoming vehicles.
Running two front and two rear lights is often a wise choice. It gives you more illumination options and there’s less chance of being left in the dark if a battery runs out.