4th August 2021
In October 2020, we put seven of the most popular and widely available rear bike lights to the test in our rechargeable rear bike light group test.
Rear bike lights from Halfords, Lezyne, Knog, Moon and Cateye were dropped, soaked and road tested to reveal the best bike lights you can buy.
Of the seven we tested, two broke completely during our tough durability assessment. But our testing found two bike lights that impressed us enough to be named Best Buys and we found that you don't need to spend lots to get a great rear bike light.
At night, it's a legal requirement for cyclists to have a white front light and red rear light on display. All of the rear bike lights we selected for testing are USB rechargeable.
A red rear bike light's sole focus is to make you as visible as possible to other road users. Rear bike lights should have a lengthy battery life and be bright enough to be seen by other road users.
Prices and availability last checked 2nd August 2021.
Key features: 25 lumen, up to 30 hours battery, four light modes.
This small and compact rear bike light has a variety of flashing and continuous settings designed to dazzle and draw the eye, a claimed 25 lumen output and up to 30 hours of battery life. It's small and light and is an Amazon's Choice bike light, but is it as bright and visible as other rear lights?
Key features: 25 lumen, up to 20 hours battery life, attaches with a rubber band.
Halfords 25 lumen rear bike light costs £10 and it's the cheapest we've tested. It claims to be as bright as much more expensive rear lights, but did it pass our durability test and is it easy to use?
Key features: 70 lumen, up to 20 hours battery life, three interchangeable rubber straps.
This expensive rear light comes with three varying sized rubber straps to help you get the perfect fit on your bike. It also has five light modes and an impressive brightest setting.
It's the most expensive rear light we've tested, but is it worth the price?
Key features: 150 Lumen, 11 light modes, up to 57 hours battery life.
With a claimed maximum brightness of 150 lumens, this rear bike light certainly claims to pack a punch. It has 11 different light modes in total and attaches via a rubber strap.
On paper it's the brightest rear light we tested, but how does that transfer out on the road? And did it pass our durability test?
Key features: 80 lumen, up to 11 hours battery life, 11 light modes, can be attached to a backpack or clothing.
Lezyne says this light will last up to 11 hours, and hits 80 lumen on its brightest setting. You can also attach it to a backpack as well as to your rear seat post.
This light is versatile, but how visible is it on a dark night, and can it pass our durability drop test?
Key features: 100 lumen, seven light modes, up to 25 hour battery life.
The power button is in the middle of this Moon light, which makes it very easy to turn on and off and change settings. It has 100 lumen to offer on its brightest setting and up 25 hours of battery life to play with.
It's easy to use, but did it pass our drop test? And how bright is it compared to the competition?
This Moon light has seven light modes, and can be mounted to the bike on the seatpost, on the bike seat rails or on a backpack via a belt clip.
Key features: 50 lumen, up to 19 hours and 30 minutes runtime, seven different light modes.
This popular rear light doesn't cost the earth, but is it robust, and does it shine s bright as cheaper alternatives?
Our researcher, who is also a keen cyclist, put seven rear bike lights through their paces in our specially designed bike lights test, which consisted of:
We put each bike light through two key durability assessments. To check for waterproofing, we doused them in a shower for five minutes, making sure each light received a steady stream of water droplets from every angle.
As well as being waterproof, good bike lights should be robust. Your light will inevitably be dropped from time to time when you're wrestling with the elastic strap on a cold dank evening. So we dropped all of the lights from the height of the handlebars, ten times, onto a hard surface. Disappointingly, not all of the lights were able to pass this test.
We wanted to see how well the stated lumen output on the packaging transfers to the road, and your surroundings, when you're riding. We attached all of these rear bike lights to a washing line pole, in the dark, stepped back and ranked them on how visible they were.
We also conducted a side on visibility test, checking the lights from a 180 degree angle.
All of the lights we tested will last at least an hour on their brightest setting. And in some cases, they'll last days on their least bright setting.
For our battery test, we wanted to do something a little different and recreate a scenario that all cyclists will have faced. The dreaded flat battery test.
We completely drained each light of all of its charge, and then gave it a quick 10-minute charge. We then timed how long the light would last on its least-bright continuous setting.
Most of the lights we tested will last more than two hours from a 10-minute charge.
It takes long enough to get ready for a bike ride as it is, so we know you don't want to spend an age fiddling with difficult straps or attachments.
Wearing thick cycling gloves, we assessed each light for how easy it is to attach to a bike, and how easy it is to remove and switch between bikes. Some lights have fiddly straps that are difficult to attach securely. The best lights are easy to attach, remove, and switch between bikes, even when you're wearing cycling gloves.
We also assessed how easy it is to turn the light on and change between the settings. Some lights have stiff buttons that are hard to use, or in awkward to reach places, particularly with thick gloves on. Whereas others are a joy to use, and easy to operate, even while you're riding.
We weighed each light, on the same set of digital kitchen scales. The weights we publish are often a little higher than claimed by the manufacturer because we include the rubber or plastic strap that you use to attach the light to the bike in our measurement, which we feel is a more accurate weight as this is what you'll actually be carrying round with you when the lights aren't attached to your bike. You can see these weights in our members only content.
For our test we chose rear bike lights that cost between £10 and £40 as this is the range the regular cyclists we consulted told us they'd be prepared to pay for a rear bike light.
We then picked widely available bike lights in this price range that are stocked in the major cycling retailers such as, Halfords, Wiggle, Chain Reaction Cycles and Amazon.
We ordered and paid for all of the lights we tested, just like you would. Which? doesn't accept freebies, which gives us the freedom to tell the truth about our test results.