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Bontrager Flare R City rear light



Small but mighty rear light with brilliant daylight mode

At every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.

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The Bontrager Flare R City rear light is a small yet mighty cube-shaped model bristling with sensors and similar tech to deliver optimum light intelligently, whatever the conditions, day, or night.

The tail light has a 100-lumen front sibling, and together they could be all some urban commuters will need. At 26g apiece, they're arguably ideal clutter-free options for summer/time trial builds, or companions for a trainer/audax bike's main lighting.

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The Flare City uses a single red CREE diode, which pumps out a very respectable 35 lumens in its highest mode. As the name suggests, the wide angle lens and reflector are designed with the demands of city riding in mind.

These components are apparently what gives it the all-important punch in daylight that other units with bigger numbers cannot match. Bontrager took its lead from daytime running lights on cars, which it says reduced the risk of accidents by 25 per cent.

Along with the usual circuitry and rechargeable li-ion cell, we have two sets of sensors. One monitors battery life and automatically kicks down to conserve power once reserves hit 5%. At this point, it will default to 2 lumens, which is more useful than those numbers suggest, and enough to limp home on until you can get hold of a charger.

The other tracks ambient light and automatically regulates output to suit conditions. Once the preserve of high-end systems, such as See.Sense's Icon rear light, we're beginning to see this filter into the mid range, and in this instance it works very well.


There are four modes in total: day steady, day flashing and night steady/flashing, and a memory function defaults to the last one chosen. The small, top-mounted switch is very positive and never felt remote, even through full-finger gloves.

The battery life indicator is sensibly positioned alongside; it runs clear when fully juiced and goes red when reserves are waning. Run in the highest, day flash, this only kicked in past the 7-hour mark.

A full mains charging takes the best part of 2 hours – tack on another 20 minutes from laptops. Thankfully, it's a very popular pattern, so should you lose the original, or leave it at home, chances are someone could lend you their android phone charger.


Most lights, especially those fuelled by fit and forget lithium-ion/polymer rechargeable cells, are accurate within a few minutes of those quoted by their manufacturers. To date, I've had the full eight hours when running the Flare R City in its day (peak) setting. This is comparatively thirsty compared with Moon's 30-lumen Gemini, which in my experience provides decent presence through town and beyond.

Night flash, which is also 35 lumens, has consistently returned 15hrs 56mins, which should be enough for most riders.

Given a few hours, in either setting, it generates quite a bit of heat. The lamp's rubberised housing certainly helps and this isn't likely to pose any problems for commuting, or short-to-middle distance training rides, but I was still quite surprised by how warm it got.

Steady day mode equates to a similarly potent 20 lumens and, once again, came close enough (2:55) to the 3hrs.

I've eaten into the 2-lumen night setting when reserves plummeted, but to date, haven't come close to testing out its cited 20hrs run-time.


Bontrager reckons the Flare R is visible to 400 metres. A bold claim, but in ideal conditions and along open roads – and given feedback from other riders and friendly drivers – in the daytime flash, I'm inclined to say it's not far off.

Through town, the more sophisticated optics produce a very pure red flare, which is equally compelling, but this intelligent firepower means approaching traffic, or other riders in a group context, aren't going to be screaming about 'arc eye'.

Its night-time counterpart seems good for around the 220 metre mark, reckon on 110 metres through town, still pretty good relative to its size. The same goes for its peripheral bite, but we are talking relative to its size. For regular nocturnal riding, I'd consider it a secondary unit, which might be a deal breaker for some.

Night steady stirs mixed emotions in me. Arguably brighter than 2 lumens might suggest (30-40 metres), it really is an emergency 'life-saver' setting rather than a proper mode per se.


The Flare R meets IPX 46 for waterproofing, which basically means heavy rain. Sure, I wouldn't go bog snorkelling with it, but ours has resisted point blank blasts from my garden hose without flinching. So long as the charge port plug has been correctly seated, I can't see most road riders having any problems.


The mount is one of those silicone strap types that does its thing and fits around all post diameters, but it is designed to point the light at 16 degrees for optimal visibility.

The light is also designed to uncouple from the bracket, a bit like a flashgun from a camera hot-shoe mount. Maybe it's just force of habit, but I found removing strap 'n' all less faff. I'm assured it's fully compatible with Bontrager's Blendr range of mounting accessories.

> Buyer's Guide: Rear lights – how to make sure you're seen 

In practice, there's enough give for mounting to some helmets, but I had no joy persuading ours to entertain seatstays and other mounting points.

Summing up, the Flare R City is a very clever and generally mighty little rear light that has quickly grown on me. However, there are better options for riders seeking a single rear light for all conditions.


Small but mighty rear light with brilliant daylight mode test report

Make and model: Bontrager Flare R City rear light

Size tested: 35 lumens

Tell us what the light is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?

Bontrager says: "35 Lumens of power and the wide visibility angle of the Flare R City tail light make you the biggest distraction on the city streets, day or night."

I say: " A tall claim but a very bright, capable light relative to its size and in most conditions."

Tell us some more about the technical aspects of the light?

From Bontrager:

* 35 Lumens provide visibility from over 400m day or night

* Wide visibility angle intended for city use

* Two day-time visibility modes and two night modes

* Day flash 35LM-8hrs, night flash 35LM-16hrs, day steady 20LM-3hrs, night steady 2LM-20hrs

* Integrated light sensor for auto-brightness control

* Battery save mode at 5% life helps ensure a safe ride home with depleted battery

* Quick connect bracket with 16 degree offset compensates for seatpost angle

* Includes Quick connect bracket and micro USB charging cable

Most tail lights use a steady flashing pattern. This pulsing is less noticeable than one that continually varies its intensity and pattern. The Day Flash setting featured on Bontrager Daytime Running Lights was created to specifically increase noticeability with varying outputs and an interruptive flash pattern.

Rate the light for quality of construction:
Rate the light for design and ease of use. How simple was the light to use?

Very user-friendly.

Rate the light for the design and usability of the clamping system/s

Very straightforward and secure. However, benefits from a little pre-stretch to begin with, especially on bigger diameter posts. On the flip side, the stock design doesn't convert to fit seatstays or other surfaces.

Rate the light for waterproofing. How did it stand up to the elements?

Passed my usual tests without missing a beat.

Rate the light for battery life. How long did it last? How long did it take to recharge?

Good, relative to output – internal sensors seem to provide some benefits here too.

Rate the light for performance:
Rate the light for durability:
Rate the light for weight:
Rate the light for value:

Tell us how the light performed overall when used for its designed purpose

Overall, the Bontrager Flare is an excellent tail light with intelligent features that offers far more presence than size or numbers would suggest. It favours those who want a daylight-specific model but is still surprisingly captivating and from a decent distance after dark. That said, those looking to run a single light and in all conditions might be better served by models with a larger surface area.

Tell us what you particularly liked about the light

Intelligent sensors, great presence for such a compact design.

Tell us what you particularly disliked about the light

Bracket, though very secure, is essentially seatpost-only.

Did you enjoy using the light? Yes

Would you consider buying the light? Quite possibly.

Would you recommend the light to a friend? Generally speaking, yes.

Use this box to explain your score

It's a small but mighty little light that is surprisingly powerful day, or night.

Overall rating: 8/10

About the tester

Age: 43  Height: 1m 81cm  Weight: 70kg

I usually ride: Rough Stuff Tourer Based around 4130 Univega mtb Frameset  My best bike is: 1955 Holdsworth Road Path and several others including cross & traditional road

I've been riding for: Over 20 years  I ride: Most days  I would class myself as: Experienced

I regularly do the following types of riding: cyclo cross, commuting, touring, fixed/singlespeed, mountain biking

Shaun Audane is a freelance writer/product tester with over twenty-eight years riding experience, the last twelve (120,000 miles) spent putting bikes and kit through their paces for a variety of publications. Previous generations of his family worked at manufacturing's sharp end, thus Shaun can weld, has a sound understanding of frame building practice and a preference for steel or titanium framesets.
Citing Richard Ballantine and an Au pair as his earliest cycling influences, he is presently writing a cycling book with particular focus upon women, families and disabled audiences (Having been a registered care manager and coached children at Herne Hill Velodrome in earlier careers)

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Sriracha | 4 years ago

"charging takes the best part of 2 hours – tack on another 20 minutes from laptops. Thankfully, it's a very popular pattern, ..."
Which pattern would that be? Has it been updated? I doubt that what was "very popular" in 2017 is still so now.

Robbiedondo replied to Sriracha | 4 years ago
1 like

It uses a micro USB, still a common standard, still popular

velo-nh | 7 years ago

I'm more than a bit suspicious over how many articles and social media posts this thing received all around the same time.  

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