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Brompton Superlight M2L-X 2 speed x Cytronex review

Covert your folder for some e-assistance on the daily commute

Our rating 
4.0 out of 5 star rating 4.0
GBP £3,155.00 RRP
Bike: £1,765 bike; B&M light kit: £95; Cytronex kit: £1,295
Brompton Superlight M2L-X 2 speed x Cytronex

Our review

This is a great option if you're an existing Brompton owner or want a lighter ebike
Pros: Light; efficient; can be fitted to any Brompton
Cons: App is only laptop-based
Skip to view product specifications

Brompton’s Electric is the folding bike companies answer to extra assistance on the daily commute, but if you either already own a Brompton or want to choose a different model as the basis for your e-assisted kicks, then British ebike conversion-kit manufacturer Cytronex has just the thing, with its Brompton-specific kit.

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This £1,295 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.

My 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 Brompton’s Electric H2L.

Even with the Cytronex and battery fitted, it’s just 14.12kg – that’s actually lighter than the e-Brompton without a battery (14.5kg). 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.

Brompton Superlight M2L-X
The kit fits neatly to the bike’s frame.
Russell Burton / Immediate Media

System addict

With Cytronex, motor power is simply controlled by a single, large bar-mounted button that you can easily switch on and off. 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.

Brompton Superlight M2L-X Speed 04
The motor is on the front wheel.
Russell Burton / Immediate Media

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 to 100 per cent, blue 50 to 75 per cent, purple 25 to 50 per cent and red 10 to 25 per cent. Below 10 per cent 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 difficult 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.

Brompton Superlight M2L-X 2 speed x Cytronex ride impressions

Brompton Superlight M2L-X Speed 05
The bike still folds neatly, as you’d expect from a Brompton.
Russell Burton / Immediate Media

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 well-balanced. 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 off.

Brompton Superlight M2L
I managed 29 miles with 300m ascent on a single charge.
Russell Burton / Immediate Media

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 disconcerting, especially on wet roads.

I did, however, quickly adjust my weight forward when riding up ramps and steeper sections of road climbs. It’s not something many folding electric rivals suffer from, with the MiRider One 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 because the average daily commute is between six and 12 miles.

Brompton Superlight M2L-X Speed 11
The power delivery is nice and smooth.
Russell Burton / Immediate Media

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 mean 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 my 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.

Brompton Superlight M2L-X 2 speed x Cytronex overall

Brompton Superlight M2L-X Speed 12
The kit is light and efficient, and can be fitted to any Brompton.
Russell Burton / Immediate Media

The Cytronex is 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 my M2L-X Superlight test bike – it’s £285 cheaper (or £335 if you fit it yourself) than the Brompton Electric, breaking down as £1,055 for the bike plus + £1,295 for the Cytronex system, fitted + £95 for lights = £2,445.

The minimal system offers 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).

I’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 I want from an everyday commuter.

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Using the Superlight as the basis it’s less of a value option, coming in at £3,155 all in. I’d stick with the H2L and make the bigger savings for the sake of a 350g weight penalty.

Product Specifications


Price br_price, 5, 3, Price, GBP £3155.00


Features br_Features, 11, 0, Features, Weight: 12.6kg w/o battery, 14.12kg with battery
Gears: Brompton 2-speed
Mudguards: Brompton
Lights: Busch & Muller AVY LED front light and Solo mudguard-mounted rear light
Brakes br_brakes, 11, 0, Brakes, Brompton dual- pivot rim brakes
Fork br_fork, 11, 0, Fork, Titanium
Frame br_frame, 11, 0, Frame, Alloy mainframe with L type titanium rear triangle
Handlebar br_handlebar, 11, 0, Handlebar, Brompton H
Saddle br_saddle, 11, 0, Saddle, Brompton
Seatpost br_seatpost, 11, 0, Seatpost, Telescopic seatpost
Tyres br_tyres, 11, 0, Tyres, Schwalbe Marathon Racer 16x1⅓-inch
Wheels br_wheels, 11, 0, Wheels, 16-inch Brompton alloy rims with Brompton rear hub and Cytronex front e-motor hub