Why do you need the best bike rear light, or best tail light if you're an American? Although the long winter nights might be gone – at least on the northern hemisphere – having the red blinker doing its magic at the rear of your bike is still recommended, regardless of light levels. Drivers are often sleepy and visibility is often poor in the mornings/early evenings, so popping the the bike rear light on before you kick off from the curb is still highly recommended.
We’ve already brought you our pick of the best bike front lights for cycling, now it’s time to look backwards. These red-hued blinkers will light up your backside like a Christmas tree when darkness falls.
They also let you join the growing ranks of cyclists who run a rear light regardless of whether it’s dark or not. After all, there’s no harm in getting on the front foot against inattentive motorists.
On the contrary, turning the little read LED blinkers on the back of the bike during daylight is especially beneficial. According to some research "it is clear that the majority of casualties occur during daylight, but there is still a significant minority that occur after dark".
So whilst you'd think you are visible enough on the bike in broad daylight, in fact you are in more danger, so having an inexpensive gadget blinking away behind you as your ride is strongly recommended, regardless of the light conditions. It's also worth noting that while many of the best electric bikes have built-in lights, a second one is still a worthy investment. Not to mention if you happen to have road bike.
The best rear bike lights, in order of preference
The Bontrager Flare RT was already one of our favourite lights but this all-new version steps things up a notch. It’s 30 per cent more powerful, with the maximum output now amped up to 90 lumens, and 36 per cent smaller, so while the light may pack a mean punch, it takes up barely any space on your bike.
Bontrager was among the first brands to pioneer daytime bike lights and the Flare RT has a specifically designed focus and flash pattern for daytime use. That, combined with the raw power of the light, apparently means it’s visible up to 2km away on the most powerful setting. Otherwise, you also have 45-lumen and five-lumen flash modes to choose from, as well as 25-lumen and five-lumen steady-state options.
The Flare RT may have one simple goal at its heart – to keep you seen on the road – but it’s a smart little light, too. The battery-saver mode provides 30 minutes of additional runtime when the juice reaches 5%, while Ant+ and Bluetooth Smart connectivity means you can pair the light with your Garmin computer.
For example, you can programme the Flare RT to automatically turn on whenever your computer is powered up, or you can keep an eye on the battery life using one of your Garmin’s data screens.
This lamp perhaps lacks a bit of brightness and battery run time, but makes up for it with very advanced features.
Able to sense traffic approaching from the rear at 140 metres, the Garmin Varia Radar will intelligently alter its brightness and flashing pattern to warn drivers that you're up ahead. Meanwhile, you receive a little audible notification every time vehicles pull up at speed from the rear, as well a visual prompt via compatible Garmin computers – Edge 1000, 820 and 520 – or an optional, slightly bulky radar device.
The computers can even show multiple approaching vehicles, each with relative speed of approach and 'threat level'. Arguably that is more complexity than most people want, but for pitch black country roads, the Radar system could be a life saver.
• Read our full Garmin Varia review
This neat little package arguably offers too much light for a rear light, which will only ever be a problem for those regularly riding in groups, but the Moon Nebula's super-bright LEDs are perfect for riders who want to alert fellow motorists to their presence.
A day flash mode gives a lower output to preserve battery levels but still affords good visibility, while the flashing night mode bangs out the maximum 180 lumens.
The light's long, thin shape might not fit every mounting requirement, although there are plenty of mounting options included in the box so you will should be able to find somewhere for it, with a bit of searching.
Think of the See.Sense ICON+ as a little computer for the back of your bike, rather than a basic bunch of LEDs, as it packs plenty of smart features to justify the above average outlay.
In short, it connects to a smartphone and bespoke app so you get low battery alerts and charge indication to your device, while GPS is used to alter the brightness and flash pattern at busier junctions.
It mounts using a simple tool-less system, and offers up to 15 hours of run time, or 2-3 at the super bright 250 lumen max output. Oh, and it's a theft alarm too – although obviously that requires you to leave the expensive light unit attached to the bike when parked.
That aside, a great light for using both day and night, while the additional smart functionality is a welcome addition.
Maximum power and brightness is achieved in the Lezyne Strip Drive Pro, thanks to five, ultra-high output LEDs stacked into one retina-scorching package.
A Mode Memory function returns to the selected mode even after turning the unit off and nine combined lumen and flash modes, including the extremely visible 300-Lumen Daytime Flash mode, make it nice and flexible for most rides. The high power output means battery life isn't the longest though.
It also boasts a unique aero and round post compatible design, so it fits those swanky carbon fibre race bikes that are popular with the evening club ride crowd.
If ever there was a more honestly-named rear bicycle light than the Knog Blinder, we are yet to come across it. It is officially one of the most eye-wateringly bright rear lights we've crossed paths with and absolutely unavoidable at night thanks to that, and to additional side illumination.
The downside is that it is a little chunky, particularly if you're mounting it to a sleek aero seat post, but it does come with a variety of clamps should that be your choice.
Fashioned from industrial grade silicone and a polycarbonate housing, it's a tough old dog, while the rechargeable Lithium Polymer battery manages a solid four hours on even the brightest flash mode.
The Cycliq Fly6 is another rear light with a twist – it's also a 1080p video camera. Cycliq's light/camera hybrids have become much more advanced in recent times, with a higher resolution, higher light output and better mounts.
Video captured from the rear of a bicycle probably isn't going to win any Best Picture categories at the Oscars, even if it is full HD, at 60fps, with a wide 135º angle lens. In fact its only use is likely to be if the worse really does happen, and you, or your next of kin, need to hold someone accountable for a rear-end shunt.
The Fly6 will 'lock' footage shot before and after it senses it is tilted more than 30° from horizontal, a bit like a car dashcam, so the video can't be overwritten.
Also included: four light setting modes, two flash settings and a maximum high power mode of 100 lumens. There's also a setting that conserves battery when it's on its last legs, giving a full half an hour to get home, according to Cycliq.
The CatEye Rapid X3 is the most powerful light in the Japanese company’s range of Rapid rear blinkers, with a maximum output of 150 lumens. That’s extremely bright, making this a decent option if you want a right bobby-dazzler for daytime visibility - although you’re only getting an hour of battery life out of that top setting.
Otherwise, the Rapid X3 has five alternative settings, with a claimed battery life of up to 30 hours for the 30-lumen flashing mode, so there’s plenty of choice depending on when and where you are riding.
The slim profile of the light and its simple rubber band mount mean the Rapid X3 can be attached to your seat post or seat stays, and the clear case ensures side visibility is impressive.
What is the brightest rear bike light?
How bright is too bright when it comes to bike rear lights? If your answer is 'nothing is too bright', consider the Lezyne Strip Drive Pro 300, a red blinker with 11 different modes and a staggering 300-lumen light output.
You might think that 11 different modes for a bike rear light is a bit of an overkill and although we agree, but we also think it provides a lot of flexibility to riders to cheese the correct output for any riding session. You might want to have the max output mode on when it's foggy and you simply can't skip a training session, while other times, especially in broad daylight, a lower power setting might just be enough.
Probably it goes without saying but the 300-lumen 'DAY FLASH 1' mode is not the most battery saving option, but even on that mode, the Lezyne Strip Drive Pro 300 will last for 'up to' five hours on a full battery. Surprisingly, lower light output modes, such as the 50-lumen 'BLAST', will drain battery life more than the retina-scorching Day Flash 1.
What is the best rear light for your bike?
For sheer weight of features, it is difficult to top the Garmin Varia Radar but but we love the super-bright and smart design of the rather more straightforward Bontrager Flare RT.
How to buy and fit rear bicycle lights
The job of a front light is, at least in part, to illuminate the road ahead, as well as to attract the attention of motorists. On the other hand, rear bike lights are all about road safety – making yourself visible to other road users.
Needless to say, the consequences of a rear-end shunt can be severe, so it’s a wise idea to invest in a bright rear light to attract the attention of those around you. In fact, it’s the law. According to UK legislation (the Road Vehicles Lighting Regulations 1989, fact fans), it's illegal to cycle on a public road after dark without lights and reflectors. You’re unlikely to get pulled over if you eschew the latter, but lights are essential.
Rear cycle lights aren't only needed at night. In low light, fog or dappled shade, cyclists can be more difficult to spot on the road, especially if you like to look chic in all black kit. The same even goes for when it’s a beautiful day as a super-bright rear light can help keep you seen when riding into a dazzling low sun.
Due to the fact a rear light is only required to act as a safety beacon, rather than providing illumination to see by, it doesn’t have to be as powerful as a front light. Twenty lumens is a reasonable starting point, but the latest and greatest lights can pump out up to 300 lumens. If you plan on using your rear lamp during the day, the brighter the better, as it has to work harder to stand out - but be careful not to dazzle other road users at night. Also look out for lights with a range of settings, so you can tailor the brightness according to the riding conditions and battery life.
Even the most powerful rear lights tend to be a lot cheaper than the brightest front lamps, with the most expensive dipping below £150, and the average being way lower. It's possible to pick up a basic but powerful rear light for less than £20 so it’s difficult to justify going without.
Fitting rear lights should be simple, with most opting for a rubber strap or a simple plastic ratchet system that clamps around the seatpost. The rubber strap is our favoured system - it's so brilliantly simple, yet reliable (when done well) and means you should also be able to mount the light on an aerodynamic seatpost, as well as a conventional round design. Today’s designs are so slick that we look back on vintage lights with their elaborate metal and plastic clamping systems and wonder, "what were they thinking of?"
Most rear lights are now USB rechargeable, so while you may need to plug it in more often than you’d have to switch a set of regular batteries, it’s a doddle to keep the juice topped up. To be on the safe side, some riders even employ two rear lights, so that if one fails or runs out of charge/battery you're not unwittingly left without. Helmet-mounted lights are another great back-up option as they can be more visible than a seatpost light, which can be obscured by overhanging jackets (watch out for that!) or panniers.
Some rear lights are also designed to attach to backpacks or clothing, once again offering the chance to increase your illumination on the road, especially as they are mounted much higher than an under-seat light for improved visibility in heavy traffic.
So, in short, there's no excuse for not lighting up. Rear lights are more affordable and brighter than ever before, so you should be able to find something that fits your budget and riding style. Now let’s take a look at the best rear lights you can get for your money.
Even more info the subject of bike rear lights can be found here: how to choose the best front and rear bike lights. For those who need just one more article before they make a purchase.