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Cars & travel.

Updated: 9 Jul 2021

How to buy the best bike lights

How bright should a bike light be? Is it illegal to ride with no bike lights. Discover the answers to these questions and how to install your bike lights
Matthew Knight
Group of cyclists at night with bike lights on

If you're on the lookout for a nice new set of bike lights, this page will give you useful hints and tips for buying the best lights for you.

Read on to discover how bright a light you need, whether a bike light is a legal requirement and tips on installation. 

If you just want to know which are the best bike lights, head to our reviews of the best front bike lights and best rear bike lights

Cycling on road at night

How bright should a bike light be?

Brightness, or the amount of light that your bike light emits is measured in Lumen. 

The amount of Lumen you'll need depends on the type of riding you're going to be doing, and where you're going to be doing it. 

If you ride on unlit country lanes you'll need a much brighter light than in an urban setting with street lighting.

Halfords 25 Lumen Rear Bike Light

How many lumens do I need for a bike light?

Rear bike lights

Rear bike lights are designed to be bright and visible to other road users. When we tested rear bike lights we found that it's possible to achieve brilliant results from as little as 25 lumen. You can get a Best Buy rear bike light from as little as £20.

Lezyne - Lite Drive 1000XL

Front bike lights

Front bike lights are a little more complicated to choose, because you have to decide whether you need a front bike light that will simply make you visible to other road users, or if you need a bit more oomph from the light to actually illuminate the road in front of you. 

If you mainly ride in built up urban areas, then a lower brightness flashing light will suffice. In fact having a light more than 600 Lumen in well lit areas can even be counterproductive to other cyclists (if you're riding in a group), as motorists looking in their mirrors may be dazzled by your bright light, making it difficult for them to see other cyclists behind, or to the side of you. 

So if you're an urban commuter and just need a light to be seen, we'd recommend a light lower than 600 lumen, with lots of attention grabbing flashing settings. For maximum visibility you can even buy two front lights and have one on a flashing setting and the other on a constant low beam. 

If your regular routes take you on dark, unlit roads, then you'll need more lumen. You'll need at least 600 Lumen to lighten up the dark and allow you to pick out potholes and other obstacles, but consider going higher than this if you can. 

We've tested front bike lights between 450 and 1600 lumen, but we found that simply looking at the claimed lumen output doesn't always tell you which lights will be brighter when you get them out on the road. 

To find out which front lights are the brightest, most durable, water resistant and easy to use, see our front bike light reviews. You can get a Best Buy from as little as £50.

Rear bike lights shining

Is it illegal to ride a bike with no lights?

If it's dark, yes. At night it's a legal requirement for cyclists to have a white front and red rear light on display.

How to attach a rear bike light

How to install a bike light

Most bike lights nowadays are very easy to install. They either have a permanent clamp that you can attach to your bike and slide the light on and off. A little more common is the type that attaches with a sturdy rubber strap. 

Some lights that attach with a rubber strap come with extra rubber attachments that allow you to achieve a sturdier grip on the bars. This is useful if you do any adventurous or off road riding with jumps and bumps. 

While most lights are easy to install, watch out for lights that are difficult to turn on and off (and switch between settings), when it's cold and you're wearing thick cycling gloves. In our bike light tests we found plenty of lights with tiny and/or stiff buttons that are difficult to operate when you're wearing gloves.

Where and how to mount rear bike light

  • You should mount the rear bike light on the rear seat post, or underneath the seat on the rail bars.
  • Make sure the bike light is free from any obstructions such as saddlebags, panniers, or even loose clothing that you might be wearing.
  • Some lights can also be attached to backpacks or clothing, but you should only do this if you also have a light attached to the bike too.
  • The rear light's flashing settings are most likely to draw the eye. We'd recommend choosing one that doesn't leave long gaps between flashes.

Front bike light installation

  • Position your front bike light as close to the centre of the handlebars as possible.
  • Ensure the light is attached tightly and securely. You don't want it moving when you hit bumps.
  • Some front bike lights can also be mounted on your helmet. But only do this if you also have a light on your front handlebars. Use a sole light mounted on your helmet and if you turn your head at the wrong moment, or look down, you could become much less visible to other road users. 
  • Angle the light slightly downwards towards the road so the centre of the beam falls on the road between 10 and 20 metres in front of you. You can also angle the light very slightly towards the curbside of the road, as this is where most of the glass, sharp stones and debris will gather that you'll want to be avoiding. 
  • Don't angle the light upwards. Firstly, much of the light will be wasted if you do. And secondly, you don't want to inadvertently dazzle oncoming traffic. Many bike lights, including some of the ones we've tested, are brighter than car headlights even when they're on full beam (c.1,200 lumen).