The LED4Si is Lumicycle's flagship road light. It's not as powerful as Lumicycle's MTB-oriented XPG systems – a claimed 1120 lumens against 1500 for the XPG – but the 4Si is designed for the road and has a tighter beam, so it can get away with less total output and get better battery life. And 1120 lumens is still a lot...
As the name suggests, the LED4Si uses four LED emitters, housed in a beautifully made, CNC machined and black anodised lamp unit. Lumicycle is clearly keen on passive cooling, with the lamp body being heavily finned for two-thirds of its length.
At the front is the lens assembly and a rather useful 'glow ring' – a translucent bezel that diffuses a bit of light around its periphery to give a bit of side visibility when riding past junctions and the like. To avoid dazzling the rider when out of the saddle, there's a little 'eyebrow' on the top edge of the casing, which works well.
The bar clamp is the usual style of hinged mount with a cam-action locking lever. It's got rubber pads inside to grip the bar, but rather than use thinner or thicker pads to accommodate different bar sizes, Lumicyle supplies an extra link to introduce into the hinge. This works well but is something of a faff – you have to push out the hinge pin and then press it back in. If you regularly swap lights between standard and OS bars I'd suggest new handlebars... The clamp bolts on underneath and offers a bit of angle adjustment to compensate for the light not being mounted dead centre.
At the back is the power socket, which is a conventional jack type. The battery is carried in a Cordura pouch with a Velcro strap – the supplied 2.6Ah battery is small enough to stow under the stem, leaving just a short run of wire. If you opt for the bigger 5.2Ah battery it'll probably need to go under the top tube. It's worth noting that the batteries come with two power leads should you want to run two light units. Some lights have more overt rubber seals and grommets at the connectors, which inspire confidence, although I didn't experience any issues with the Lumicycle in the rain.
Next to the socket is the switch, which is a momentary-action up/down toggle rather than the more usual push button. In terms of usability, the switch is borderline genius – flick it up to make the light brighter, down to dim it. Obvious. It's easy to find, too, because it sticks out. There are five modes in total, with the usual low, medium and high being supplemented by a full-bore 'Smart Boost' mode and a flash setting.
Smart Boost unleashes the full 1120 lumen power of the LED4Si, but only for three minutes in the interests of battery life and heat management. If you know you're going to need lots of light for longer, a long upward push on the switch from High locks it into Smart Boost mode until it either overheats or the battery gets depleted. If either of those things happen the light switches itself down to a lower setting. When the battery's getting properly empty you won't be able to access anything more potent than Medium, although that's ample for most purposes on the road – I was comfortable at late-teens speeds on unlit country roads with it, with High and Boost still in reserve for descents. The beam pattern is fairly tight, although still with a healthy degree of peripheral illumination. It carries well and appears to be directional enough to not dazzle other road users.
A single LED acts as a status indicator and battery gauge, with steady colours (green, yellow, red) telling you how the battery is and overlaid flashing telling you what setting you're in (assuming that you can remember which colour means what). With fairly aggressive use of the higher-power modes, I was getting around six hours out of the LED4Si, which squares with Lumicycle's claimed numbers of 10 hours on medium, four on high and just over two on Boost. The 'smart' auto-cut-off charger fills the battery back up in about three hours. If you need to charge in two locations you'll need to remember to take the charger or get a second one – there's no USB charge option.
The Lumicycle LED4Si is a very good light indeed – top-notch construction, great performance, decent battery life. It's in the premium price bracket but it's a top-quality product. I'd be tempted by the LED3Si, though – one less emitter, better battery life but £65 cheaper...
road.cc test report
Make and model: Lumicycle LED 4Si
Size tested: Black
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?
"The LED4Si has the most penetrating, intense beam of all the Lumicycle lights making it most suited to fast road riding," according to Lumicycle. Hard to argue with that, really.
Tell us some more about the technical aspects of the light?
Four LED emitters are housed in a rather lovely CNC-machined alloy housing that's generously endowed with cooling fins. A translucent bezel at the front passes some light to the sides to help other people see you, and an "eyebrow" on top prevents any light spill upwards that might dazzle you while riding. At the back there's the power socket, status LED and a rubberised toggle switch. The test system had a 2.6Ah Li-ion battery -- there's a 5.2Ah unit available if you need more run time.
The LED4Si is beautifully made and finished. The lamp housing is CNC-machined aluminium, anodised black. The bezel is secured by four tiny Torx bolts and everything's weather-sealed. The battery lives inside a simple Cordura bag with a Velcro strap to attach it to your frame or stem.
Lumicycle uses a very intuitive control system on its LED lights. Rather than a push button, there's an up/down toggle switch. Hold it up to switch on, and then flicking it down switches to a lower output and flicking it up switches to a higher one. It's slightly complicated by the presence of a flashing mode (long press down from off) and the Smart Boost extra-high-output mode (which turns itself down after three minutes unless you lock it with another long up press) but fundamentally it's an excellent system. The LED uses a mix of colours and flashes to communicate both power level and battery state, if you can remember what means what.
The clamp is the common hinged, cam-lock design, with rubber pads to aid grip. Oversize bars are accommodated by adding an extra link in the hinge, which works well once done but is somewhat more fiddly than swapping rubber pads around.
No problems during the test, although the power connector is a standard jack with no particular extra protection. There's no reason to expect any issues unless you start pulling the plug out in torrential rain, but there are lights out there with more overt seals around the connector.
Claimed run times range from 31 hours on low to 2.2 on Boost -- I got over six using a mixture of Boost, high and medium, so Lumicycle's numbers look entirely plausible. The light comes with a smart charger that cuts off when the battery's fully charged, which takes about three hours from flat.
With up to 1120 lumens on tap and a well-designed beam pattern, the Lumicycle is a great performer. The medium setting is fine for most purposes, with high if you're cracking on and Boost still to come.
It's hard to assess durability during a relatively short test period, but the Lumicycle is solidly made and we're not aware of any issues.
At 400g for lamp and battery, the Lumicycle is a decent weight but not class-leading -- Exposure's all-in-one units are significantly lighter, with the roughly equivalent Toro, for example, being a claimed 100g lighter.
It's definitely in the premium category, but this is a very well sorted light. For my money, Lumicycle's own LED3Si is a better value proposition, though -- doing away with one LED emitter doesn't make as much difference as you might think, it still has ample power, you get longer battery life and it's £65 cheaper.
Tell us how the light performed overall when used for its designed purpose
Excellent -- there are more powerful lights out there on paper, but the Lumicycle is definitely powerful enough. The beam strikes a good balance between spread and penetration.
Tell us what you particularly liked about the light
The up/down toggle switch is brilliant -- it's easy to find in the dark and it's very intuitive.
Tell us what you particularly disliked about the light
Self-contained lights are always going to be neater than having wires and battery bags dangling off the bike, and changing the clamp between standard and OS bars is a bit of a faff.
Did you enjoy using the light? Yes
Would you consider buying the light? Yes, although I'd probably go for the cheaper LED3Si
Would you recommend the light to a friend? Yes
Anything further to say about the light in conclusion?
Lumicycle doesn't seem to be as well known as Exposure, but its products are every bit as good (and in some respects better) if you don't mind plug-in battery packs. Excellent.
About the tester
I usually ride: Whichever's nearest the door My best bike is:
I've been riding for: Over 20 years I ride: Most days I would class myself as: Expert
I regularly do the following types of riding: cyclo cross, sportives, general fitness riding, fixed/singlespeed, mtb, Track; to the shops; with the kids