LET THE SPARKS FLY!
For your folding ebike kicks, do you go factory fit or conversion? We put Brompton’s assisted folder up against the lightweight conversion from Cytronex
When it comes to folding bikes, the Brompton is ubiquitous. It’s an incredibly successful brand thanks to the cleverly compact fold (565mm high x 585mm long x 270mm wide) and simplicity of use. When it comes to electric folding machines, however, it faces sti er competition. We’ve recently tested ebikes, such as the budget EMU, funky MiRider One and the luxury GoCycle GXi, which all performed impressively. Brompton partnered with Williams Advanced Engineering (of Formula 1 and Formula E fame) to develop its bespoke ebike system, which comprises a large front-hub motor and a smart-looking battery – housed in its own bespoke cordura bag. This slots into a bracket mounted on the head tube and can be removed and carried over the shoulder when your bike is folded.
Brompton claims a range of between 20 and 45 miles from the 300Wh battery, depending on rider and topography. The battery weighs in at 2.9kg for a total 17.43kg. Without the battery the bike is 14.5kg compared to the standard Brompton’s claimed 11.35kg. Brompton’s system will have the added usability of an app, but at the moment it’s “being aligned with Brompton’s up-to-date systems and website”, so a search for the app on your app store will be fruitless.
If, however, you’re either already a Brompton owner or want to choose a di erent model as the basis for your e-assisted kicks, then British ebike conversionkit manufacturer Cytronex has just the thing, with its Brompton-specific kit. This £1295 kit contains a new front wheel with e-motor hub, the battery pack, charger, wiring loom and bottle cage-style mount. This price includes fitting and, rather than using the strap-on battery mount, Cytronex will add bottle bosses to the frame for a neat and secure fit. The company tells us a competent home mechanic can fit the kit themselves, in which case you save £50.
Our test bike is the Black edition of Brompton’s two-speed Superlight (SL). The SL replaces Brompton’s standard steel fork with titanium and adds a titanium rear triangle, too, which drops the standard bike weight to just 11kg. That’s 350g lighter than the basis for the e-Brompton’s H2L. Even with the Cytronex and battery fitted, it’s just 14.12kg – that’s actually lighter than the e-Brompton without a battery. Without the lightweight 1.51kg battery, it’s an impressive 12.6kg thanks to the lightweight Cytronex kit. It’s a great option for a bike you’ll end up carrying quite often on your commute.
SYSTEM ADDICT
With Cytronex, motor power is simply controlled by a single, large bar-mounted button that you can easily switch on and o . You cycle through low, medium and high assistance (green, blue, red) with a single push of your thumb and hold as it cycles through the modes.
Cytronex’s single sensor is a patented design. Usually ebikes have up to three sensors – one on the
crank to measure cadence, a speed sensor (to limit speed) and a brake sensor to cut the motor when stopping. Cytronex’s clever single sensor collects information by pointing at the largest sprocket on your rear wheel. It senses the movement of the teeth on the cog and the rate at which they’re turning to deliver power; when you stop pedalling and freewheel it cuts power. Positioned behind the stay, it is well shielded from knocks too.
Speed calculations are made on initial setup. The battery is plugged into a laptop (PC or Mac). Then use Cytronex’s app to set up the system (wheel size, legal limits, sprocket size etc). Use this app to tune the power delivery to your preferences and change the brightness of the light indicators on the control button.
Battery energy reserves are shown by a light on the battery itself, with green meaning 75-100%, blue 50-75%, purple 25-50% and red 10-25%. Below 10% and it flashes red. This turns on the low-battery mode, extracting the last of the energy by stepping down the power gradually. For the most part, it works well, but as the battery sits low on the frame’s main tube, it can be di cult to see the small LED indicator.
Cytronex also has an option for a set of Busch and Muller lights, £95, which are wired into the system.
These are also controlled by the bar-mounted button and cleverly hold enough in reserve to maintain light power, so even if you run the battery down to zero, you won’t be left in the dark.
NIMBLE AND BALANCED RIDE
The Cytronex Brompton is a pleasure to ride. The bike’s low weight retains the same light-steering feel of a Brompton, which is great for low-speed manoeuvres. Impressively, it’s incredibly wellbalanced. That’s no mean feat for an ebike, and is down to the relatively compact front-wheel motor and a battery that’s centrally mounted on the main tube. The result is easy, neutral handling.
The battery fits via the dedicated bottle cage with Cytronex adding bosses to the frame for you
(if you fit the kit yourself, you’ll have to make do with the removable mount, but it’s unobtrusive). The Cytronex’s smaller, lighter motor, compared to the electric Brompton, still delivers plenty of punch through its three settings, and having the bar-mounted button encourages you to mix modes throughout your ride, popping into high (red) when you’re heading uphill or dropping it down to eco (green) on the flat, or even switching it o .
The downside of the system stems from Brompton’s natural riding position, which is fairly set-back with little weight over the front wheel. That’s fine for normal riding, but hit a steeper slope with the assistance on and the front wheel can ‘unweight’ enough to create a hint of wheelspin, which is
CY TRONEX'S CLEVER SENSOR COLLECTS INFO BY POIN T ING AT THE LARGEST SPROCKET ON YOUR REAR WHEEL
BOTH BIKES THE ELECTRIC AND THE CYTRONEX DO A GRE AT JOB OF NOT COMPROMISING WHAT M AK ES A BROMPTON A GRE AT COMMU T ING BIK E
disconcerting, especially on wet roads. We did, however, quickly adjust our weight forward when riding up ramps and steeper sections of road climbs. It’s not something many folding electric rivals su er from, with the mini MiRider being rear-wheel drive and the clever GoCycle coming equipped with traction control to prevent the front wheel spinning.
Cytronex makes no claims on potential range, but it turned in a fine 29 miles with 300m ascent. That’s plenty as the average daily commute is between six and 12 miles. As for delivering that power assistance, each level feeds in with a nice upward trajectory closely matched to your cadence. Because the system senses from the rear sprocket, it applies power only when you do and cuts out as soon as you start to freewheel. It makes for a natural feel and one that conserves battery life, meaning the Cytronex’s relatively small 180Wh battery can match the range of far bigger units.
Where the Cytronex really scores, however, is how well it works with Brompton’s folding party trick: the bottle battery’s small size and central placement means it can be left in place when you fold the bike. And because the battery only weighs 1.51kg, it’s as easy to carry as a standard Brompton. Though our
Cytronex kit came fitted to a lightweight Brompton, the standard bike that the Brompton Electric is based on only has 350g more weight in its frameset. You can, of course, quickly remove the battery and stow it in a backpack, meaning you’ll be carrying an 11kg folder.
SIMPLE BUT EFFECTIVE
Brompton’s Electric has a much larger hub motor built into its front wheel, while a dedicated bracket on the head tube accommodates the rectangular battery. The quick attach-and-release fitting is clever and we like that the system boots up as soon as you engage the battery. The battery has two buttons – the right one cycles through power levels; the left one operates the lights. There’s a central arc of five LEDs to show battery charge level. It’s a simple system and one that doesn’t require hours of poring over a manual.
The lack of a bar-mounted controller is a shame. Yes, reaching down to operate the waterproof buttons is easy, but any time you take a hand o the bars or eyes o the road isn’t exactly ‘urban safe’. Hopefully, Brompton’s app will o er in-use control of the system because a phone mounted on the handlebar would be preferable to the current system.
In its top setting, the Brompton’s power delivery is somewhat punchier than the Cytronex, albeit it does feel overkill for most situations. That said, it’s fun to switch into full-power mode and beat other riders – and even other automobiles – at the lights from a standing start. Like most ebikes, the Electric lived most of its time in the middle setting, which o ers
IT’S FUN TO SWITCH INTO FULL! POWER MODE AND BEAT OTHER RIDERS "AND CARS" AT THE LIGHTS FROM A STANDING START
the best balance of ascending power with plenty of range.
The Brompton Electric peaked at 24 miles (39km) with 342.5m climbing. That’s in-line with its claimed 30-45km range. We’d say with a relatively flat commute, the Electric could easily achieve 45km. The bike handles well, though it still su!ered from a bit of wheelspin on steep ramps, but the overall feel is positive. The power assist gives plenty of sweat-reducing assistance and does so with no jerkiness. It closely matches your pedal stroke to smoothly deliver power throughout its range of modes; there’s no overdoing torque so you always feel in control. The Electric has a 300Wh battery, which is 120Wh more than the Cytronex, but its smaller range suggests the bike’s weight consumes more of this capacity than the e"cient, compact Cytronex conversion uses.
As for folding, you first need to remove the battery. That’s simply a button push on the battery bag’s integrated handle and a quick pull. We appreciate that Brompton has added a pocket to the battery bag (which has a shoulder strap for easy carrying) that is big enough to hold the bike’s compact charger and cable, meaning you could commute 20 miles each way and charge the battery at your desk.
That’s something that would be much trickier with the Cytronex’s rather bulkier charger, which contains a rectangular power pack and a large, round base for the battery to sit into. Throw in added cables and you’ll be consuming a fair bit of luggage space in your backpack. It does mean, however, that transporting your folded Brompton Electric entails carrying both bike and battery bag. Also, the Electric is carrying a fair amount more weight than the Cytronex conversion, so you’re hauling a 14.12kg folded bike, plus a 2.93kg battery and, of course, whatever other luggage you need.
HE ELECTRIC CLOSELY MATCHES YOUR PEDAL STROKE TO SMOOTHLY DELIVER POWER THROUGHOUT ITS RANGE OF MODES
AND THE VERDICT IS...
Both bikes do a great job at not compromising what makes a Brompton a fantastic commuting machine. The in-house Electric features a clever system with a quick-release battery in its own carry-bag, so the fold is unobstructed. The power delivery is good and the range impressive. With a bar-mounted controller, we’d find little to fault.
As for the Cytronex, it’s a very well-thought-out conversion kit and its light weight is a bonus. The price is, too. Fitted to an equivalent Brompton H2L 2-speed – as opposed to our M2L-X Superlight test bike – it’s £285 cheaper (or £335 if you fit it yourself) than the Brompton Electric, breaking down as £1055 for the bike plus + £1295 for the Cytronex system, fitted + £95 for lights = £2445. The minimal system o!ers enough range for most commuters, fits in such a way that it can be folded complete and adds much less weight so it’s still carryable at 14.12kg (with battery). We’d like Cytronex to have a mobile-based app for convenience but, as it’s stands, it’s simply robust and reliable, which is just what we want from an everyday commuter. Using the Superlight as the basis it’s less of a value option, coming in at £3155 all in. We’d stick with the H2L and make the bigger savings for the sake of a 350g weight penalty.