Bontrager Flare R City rear light

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.

Modes

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.

Run-times

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.

Output

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.

Weatherproofing

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.

Mount

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.

Verdict

Small but mighty rear light with brilliant daylight mode