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SEVEN DAY CYCLIST
CYCLING, BUT NOT USUALLY RACING
LATEST UPDATE NOVEMBER 26th 2025
HOW DO WE REACH THE OVERALL RATINGS FOR PRODUCTS WE REVIEW?
Gaciron Loop 100 Smart Brake Taillight 57g complete £21
The Gaciron Loop 100 Smart Brake Taillight is a small but surprisingly mighty six mode model with braking and auto stop start functions. Output is more impressive than size would suggest and broad enough to tackle town, suburbs and back roads. Plastics employed in the mounting hardware feel a little low rent, but are perfectly serviceable in practice and the light itself feels suitably robust (I've accidentally dropped ours onto a concrete floor from a metre with no hint of damage.) Improved plastics, especially in the saddle rail mount would be welcomed, but minor points, taking everything into account.
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Pros: Sensible range of modes for most conditions, impressive output relative to size, meets IPX6 for weather proofing, responsive stop start & braking sensors, several mounting options.
Cons: Switch trickier to locate wearing full finger gloves, composites could be sturdier.
Specification
Measuring a diminutive 33.5*33.5*30.2mm, the light is made from anodized CNC machined aluminium and meets IPX6 for weatherproofing - everything bar immersion essentially, which is welcome for road duties and ass peace of mind off road -provided you're not river crossing, or bog snorkelling. Inside we have COB diodes for maximum impact, projected through a polycarbonate lens with reflectors further boosted by "Saturn" type rings around the periphery for a "starts and circle" effect. These are powered by a rechargeable 420mAh lithium-polymer cell reckoned capable of up to 500 charge cycles before capacity drops by 20%.
Mount 3/5
Two mounts are included within the box - one for seat posts, stays and similar curved hosts, the other for saddle rails. Both employ magnets for very secure tenure between light and brackets-I've had no issues on, or off road. The post secures courtesy of the familiar rubber "doughnut" type strap. There are two, to suit different tubing diameters and are easily replaced, should one get lost, or eventually fail. Given the light's size and my tendency towards rack top bags, I've gone for the post options but aside from my comments regarding the plastics, its slots together reliably enough-just add a drop of grease, or wet lube to the Allen screw threads when assembling.
The mount and light's magnets are a very reliable union, meaning you may need to pull harder than expected when removing the light to charge, or when locking up in the street.
I'm pleased to report the post mount has proved compatible with rack tubing and hasn't presented issue with 20 litre panniers.
Modes & Switch 3.5/5
Those six modes then. We have three steady 30, 15 and 5 lumens (High, Medium and Low). Trail mode is a quick tempo 15 lumen flashing, Fog is a high intensity 100lumens, which would also be a good fit as a daytime running option. Finally, there's a power saving mode, which is a low, slow-paced flash for those times when you either don't need the power or need to conserve juice. Whatever your selection, the memory function means it will default to that.
Now, the braking mode. This is another 100 lumens and works to much the same principle as everyone else's. The light detects slowing and so pumps out the 100lumens for 3 seconds. Mercifully, it can also be disengaged. Ensure the lights on, then press the switch for three seconds until the light flashes three times.
Do the same to reinstate the braking function. Finally, there's a smart sensor, which will kick in, turning the light into hibernation. If it senses movement, it'll re-engage and in your last mode. Subsequent, singular prods cycle through the modes. Smart functions aren't essential but really handy if you're forgetful or just pulling for a rest-stop. Official run times are 40 hours (Power Saving auto stop-start), 24, Trail mode, 10 hours fog (100 lumens), 20 hours low steady, 12 hours medium steady and 5.5 for high steady.
As for the switch, its mounted dead centre of the lens and is up to the job but tricky to locate wearing winter weight full finger gloves. On the plus side, it requires a definite, sustained prod to power up and down - unwanted power ups in a bag or pocket have been a moot point to date.
Output 3.75/5
Generally impressive, thanks in no small part to the COB (Chips on Board) layout. Mounting diodes directly to the circuit board allows manufacturers to maximise the number occupying an area. Flashing modes are the most eye catching and as I said earlier, the 100 lumens "Fog" serves as a very effective daylight running option with enough punch to cut through bright autumnal sunshine. Consensus from approaching riders suggested you wouldn't want to be wheel sucking, and the sprightly tempo was obvious from 125 metres, further on overcast outings.
On some very dark nights, I've employed it to good effect, a neighbour reckoned they could spot it from 250 metres and despite the lens’ relatively flat profile, peripheral throw was surprisingly effective- welcome when passing concealed driveways and unlit rural junctions. Daylight running mode aside, overkill to the point of retina tickling through built up areas-especially in slow moving traffic. In this context, I've found the high quick 15 lumen flashing struck an optimal balance between presence and frugality.
Compared to lights with larger surface areas, it's less obvious along unlit roads but other riders suggest visibility to 100metres on clear nights, dipping to 85 when things turn cloudier. The low steady has its place-either as backing singer to a more powerful rear light, or in moderately lit areas.
The slower tempo has left me feeling less conspicuous at roundabouts and bigger junctions, although this is less problematic with the braking function engaged. on the open road, other riders reckoned they could spot me from 40 odd metres (with the braking function disengaged) so viable option, should you find yourself forgetful on the charging front, or needing to drop down on a long ride.
Steady modes are, in my view very sensible. The 5 lumen low sounds a bit low but arguably a good bet for group riding-assuming you weren't at the back, where I'd either go for the medium 15 lumen, or one of the flashing options. Again, round town, if you're forgoing the braking function, 5-lumen low is best suited to shared use paths and less trafficked areas. 20-30 metres was the consensus. 15 lumens has enough clout for semi/rural contexts, fine for the sticks with the braking on, but ideally, I'd go for the 40, which consensus suggests could be spotted from 80 metres on a clear night.
Charge/Run Times 3.5/5
Charge times are quoted as two hours from pancake flat to fully juiced. From a USB port on the ‘puter, yes, bargain on 10 or 15minutes quicker at the mains. Either way, red denotes refuelling, steady blue, fully charged.
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Braking function off, run times have been within 6 minutes of those cited and in temperatures between 15 and 3 degrees. Braking function has an impact, no more significant than others I've tested in recent years. While its reassuringly responsive, expect more frequent engagement if you're regularly riding in hillier regions, in stop start traffic (especially if towing a trailer, or tagalong) and a subsequent dent in run times. Difficult to measure this scientifically, but on rides of several hours with a mix of quick descents and slow climbs, run times dropped by 15-20%, depending on how weary my legs were feeling.
Durability/Care 3.5/5
I’ve accidentally dropped ours from a height of one metre-accidentally and no ill effects to date - not even marked anodising. Ours has been splattered with the usual crud, exposed to heavy rain and of course, soaked with warm sudsy water with no ingress, or corrosion. Reassuring, although not surprising, given the IPX6 rating and snug fitting port cover.
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​Other than keeping the battery charged and possibly replacing the doughnut type strap, there’s no reason it shouldn’t prove reliable, long term.
Value 3.75/5
£21 (presently reduced to £16.71) given the specification is favourable, especially for a light employing brake lights and other sensored tech. Oxford Ultratorch R50 Slimline Rear Light R50. £17.99 buys eight mode, including a particularly effective, frugal flashing. However, there’s no braking, or sensored functions and it only meets IPX4 for weatherproofing. Magicshine SeeMee 100 Bike Taillight V2 comes in at 23.99, boasts a maximum of 100 lumens, a braking and stop-start on/off function, ambient light sensors, IPX6 for weatherproofing, saddle rail and post mounts, 1.5 hour charge times and an auto kick down, when reserves tumble.
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Cat-Eye Tight Kinetic Rear Light is £22.99, meets IPX7 for weather proofing and employs a single AAA cell, which are pretty ubiquitous and easily replaced. Blessed with a reasonable surface area and translucent lens, its reasonably bright. However, there are only three modes, and the braking function cannot be switched off, which may be a deal breaker.
The Sigma Blaze SIGMA BLAZE REAR LED LIGHT | cycling-not-racing is another competent, surprisingly bright option, assuming you didn’t want a flashing mode and will return decent run times. However, it’s a couple of quid dearer and yep, you can’t disengage the braking function. Staying with Sigma, I’ve been impressed by their RL150. It boasts 150 lumens day mode, braking function and a super frugal eco flash. However, the braking function cannot be disengaged, it only complies with IPX4 for weatherproofing and is the best part of £9 dearer.
Summary
While adequate, the composite mounts could be a little beefier and are something I’ve like to see revised, even if it meant adding a couple of quid to the ticket price. Decent output, size and favourable weight mean I’d be happy to run the loop as my only rear light for on clutter-phobic road, (or TT) builds - or indeed, getting home at dusk, following a fun afternoon along the trails. Characteristics, coupled with favourable pricing lend it nicely to “backing singer” companionship to dynamo or bigger battery model for tackling long, steady miles along pitch black lanes.
Verdict 3.5/5 Compact light with decent output, sensible modes and very appealing price tag but mounting hardware merits improvement.
Michael Stenning
PUBLISHED NOVEMBER 2025
