SMART GEM REAR LIGHT

40g (including batteries) £9.99

The Smart Gem Rear Light is a very affordable, user-friendly model; one that packs a mightier punch, in fast flash than 10 lumens would suggest. That said, I’d be inclined to use it as a companion to a dynamo, or more potent blinker, especially for the backroads. 

Pros: Inexpensive, user friendly, brighter than lumens suggest.

Cons: No option for clothing, or luggage mount.

Materials/Specification

This is a very simple, single diode, amplified through a simple composite lens. No swish collimators/similar optics here. The Lens, like several doubles, as a switch; a great idea, especially in winter, wearing full-finger duvet type gloves.

A definite double press engages the light, subsequent prods cruise through the modes and another, double press powers down. There are three modes. Steady, flashing and pulse flash.

It's marketed as 10 lumens. There's no memory function, but then there’s hardly call for it.

Build quality from plastics is pretty good, especially given it’s described as “water resistant” and doesn’t carry an IPX accreditation.

The Gem runs from two CR2032 button cells. Replacements are readily available at off-licences, supermarkets and even petrol stations (assuming you didn’t keep a couple stashed away somewhere). Afterall, not everyone can refuel their lights and other tech, from work. Smart cites run times as 60hours (flashing) 20 hours (pulsing) and 18, in Steady mode.

Access is simply a matter of rotating its back panel in the prescribed direction, whereupon the cells can be scooped out with a thin flat bladed screwdriver. The sort common to multi-tools.

Mount 2.75./5

This is a simple watch strap type, designed to accommodate various seat post diameters. I’ve also successfully tethered ours to a couple of helmets, and my fixed gear winter/trainer’s seat stay. However, it’s been “supported” by the otherwise redundant cantilever boss. Pencil thin tubing has been a non-starter, and I was mildly disappointed by the lack of “clothing clip."  In fairness, it has offered limpet-like tenure to 25.4, 26.6, 27.0, 27.2 and 31.8mm posts.

Weather Proofing 2.75/5

Ours has been subjected to rain and wet roads, without missing a beat. I’ve also given it a good few, sudsy bucket drownings, followed by close-range tickling with the garden hose. These coincided with bike washing/rinsing. No obvious signs of ingress have resulted. Mind you, I’d be inclined to give the battery contacts a precautionary trace of silicone grease/Vaseline. Especially on bikes shunning mudguards.

Output 2.75/5

As a benchmark, I regard 15 lumens the lower end of the power spectrum, for unlit roads and indeed. Save for contingencies, the Gem felt a little (emphasis on the little) underpowered as a solo rear light, through the sticks. 

That said, fast flash was distinctive enough, keeping me on the radar at around 35 metres, on a relatively clear night. Indeed, it’s been a godsend on some dusky evening’s when I’ve been out longer than initially intended.

Round town, this dropped to 20-25 metres given the competing illuminations and peripheral punch is middling. Not that I’ve ever felt stealthy when tackling roundabouts and other junctions, given the flashing pace but it’s worth bearing in mind.

 

Helmet mounting boosted this, by a few metres.

Pulsing is slower and thus ideally paired with something slightly brighter, given the slower sequence. Friends, on two wheels and four reckoned they could spot me at 25 metres along the lanes, on relatively clear nights. However, I tended to slip off the radar. Round town, this dipped to 18 and the sequence too long for comfort. Not a major problem on dual use paths perhaps. However, it left me feeling decidedly vulnerable, tackling roundabouts and junctions after dusk.

Though I’d never use the gem as a primary rear light on tagalongs/trailers, it’s proven a very useful backing singer to Fibre Flare   and those with braking functions, such as Xeccon Mars 60 COB Rear Light . 

Steady is better than I expected and had more presence than pulsing. 25 metres on a clear night and along unlit roads Predictably it saps more juice too. Alternating between the three settings, I managed 16hrs 53 from the factory cells, and 17.02 from a “pound shop” replacement. Not far off the 18 cited. Pound shop specials also returned 19.23 in pulsing and the final set are well past the 35hour mark, alternating between flashing and pulsing.

Value 3/5

Minor points aside, part of me says “What do you want for a tenner?” Indeed, we’ve seen it for £7.99 online, and at that price, its arguably an absolute bargain. That said; if my budget only stretched to one rear light, I’d go for the Smart Superflash 317 0.5 watt Super Bright Rear light are a notch or two up on the Gem, helped in part by the larger surface area.

I’ve an older unit that served a good 7 years and is still in pretty rude health, despite being (unintentionally) drowned and indeed, dropped a few times. AAA cells are even easier to replace, and it also features a clothing/luggage clip. Store branded models, including BTWIN boast 2 year warrantees and could also give it a good run for your money.

Conclusion

I’d be inclined to buy two Gem to compliment a more powerful “main” light, on a trailer/tagalong. Reasonable output and presence, not to mention price-tag lend it well to town hacks. Or as a contingency light, for extended summer playtimes on the best bike(s).

Verdict: 2.75/5 Cheap and generally cheerful rear light but best as a secondary/contingency option. 

Michael Stenning

https://www.bob-elliot.co.uk/

PUBLISHED SEPTEMBER 2019

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