Surly Big Dummy - CYC Photon ebike mid drive conversion kit

Surly Big Dummy - CYC Photon ebike mid drive conversion kit


If it isn’t clear that I’m a fan of ebikes for UTE-ility purposes, then check here or here or just google ‘FYXO Tonka’. 


Carrying cargo, kids, runnings errands, dinking your partner on date night, commuting - forget the financial benefit, one benefit that cannot be easily quantified is how much fun and hassle free they are. 

If the financial jump to an off-the-shelf ebike for cargo or commuting is out of budget, or you’d just like to put your toe in the water first - a mid-drive kit can be a relatively inexpensive way to convert an existing bike you may have. 

The overwhelming majority of the conversions I’ve built have used Surly’s for the chassis.  They are robust, and already have a bazillion mounts for adding fenders, racks, cages and the like.

Until now, I’ve only used Bafang mid drive motors - a great option for conversions, albeit with a massive shortcoming - no torque sensing. 

In layman's terms, for cadence based motors (Bafang), once you turn the cranks, the motor drives the chainring depending on the level of assistance you determine.   This experience can feel more like an electric scooter than riding a bike.   From a psychological perspective, other road users are familiar with seeing legs go up and down when spotting a ‘cyclist’ and static legs indicate that it’s not a ‘bike’, and throws them into the category of e-scooters, e-skateboards and other motorised mobility devices.

A torque based system matches a percentage of the effort you put into the pedals for a ride experience that resembles an analog (non-motorised) bike.  

Don’t ask me how the CYC Photon came across my radar, blame the algorithm, but once I saw it, I knew I had to have it. 


It is smaller, more than half a kilo (1.5lbs) lighter, and still delivers 750w of power and an eye-watering 110Nm of grunt.  Aesthetically the finish is much nicer, and the absence of gear sensor and brakes sensors make for a cleaner setup.

The major appeal to try the CYC Photon was a sophisticated Gen 3 torque sensor, and an app for programming pedal assist and motor settings on the fly.   Normally this would require an 'Eggrider' display for Bafang motors which pairs with an app to modify settings.   Having used the Photon for more than 6 months, with the torque sensor it’s closer to a Bosch / Shimano system in terms of ride ‘feel’.

The included CYC chainring is a high-quality narrow wide available in 38 and 42, or an additional $50 for the smaller 34t or bigger 50t.    The CYC crank arms are available in 165 & 175mm and on par with Lekkie Buzz bars in terms of strength and quality.    The cranks use an ISIS taper spindle, with a sealed bottom bracket and are leagues above other mid-drive systems in terms of quality.

The stock Bafang chainring belongs in the round file, and the cast alloy cranks are also very basic, and I factor both crank and chainring upgrades into any build using a Bafang.

Once you compare the systems side by side,there’s only a small premium to pay for the Photon with a ride experience that eclipses its rivals.

The motor is smooth, powerful and whisper quiet.   I was confident from using my own ‘test rig’ to sway TOM, the owner of this custom build to go with the CYC motor.

In terms of installation, the CYC Photon is even easier than the Bafang platform.  Scan the QR code on the manual and you’ll find PDFs and YouTube videos to assist you.    Remove the existing crankset, install the motor unit with the appropriate spacers to suit your bottom bracket and then connect the motor to the battery.  It’s that easy.  The motor uses an XT90 plug for the power, another cable for the speed sensor (which is also the bluetooth sensor) and the display / throttle control cable.  Both Bafang and CYC systems offer a throttle, which is another item that belongs in the round file on a ‘bike’. Just my 2c. 

Besides the included pin spanner, you’ll need a set of hexs and a bottom bracket wrench to secure the motor in place. 

The CYC Photon is capable of using 36, 48 and 52V batteries.  This build used a 48V 17ah battery, housed in the Blackburn Outpost frame bag and this is the first build where the fit (Medium-Short) hasn’t perfectly matched the inner triangle.  C’est la vie.

Concealed in the bag are the cables for the motor, a spare XT60 output, switch and wiring for the front / rear lights, and thanks to a nifty little right angle USB dongle which sits flush with the battery, power for the Quad Lock wireless head to charge your phone while riding.  


Concealed in the bag are the cables for the motor, a spare XT60 output,  switch and wiring for the front / rear lights.


Thanks to a nifty little right angle USB dongle which sits flush with the battery, power is fed to the Quad Lock wireless head to charge your phone while riding.  



The CYC Ride Control App gives you a heap of live data should you need it, motor power, human power, motor and controller temperature, battery levels and more. Ultimately it's best used for fine tuning your ride experience.   

The pedal assistance can be varied for power and torque with two usage modes - STREET and RACE.  One for sticking within the legal limits of road use in your country (25kph / 15mph in Australia), the other for off-road use.  These two modes are toggled from the controller, and settings defined in the app.


You can also adjust the torque sensitivity, ramp up time, and motor assist factor. Strangely, the wheel circumference and the number of assist levels is set on the controller.   I find 3 levels ample, 5 justifiable, and 9 overkill. 






The million dollar question I always get is ‘how far can you go on a single charge’ and this heavily depends on how much of a lead foot you are with the assist, terrain, wind, load and the like.  It’s expect 50km+ (30mile) out of single charge without being frugal with assistance but again, depends on where you live, how you ride, and what your are carrying.  


Speaking of carrying - the front rack is Blackburn with a lock holster, and will easily carry two cases of wine, or a small child.    A cargo net (not pictured) secures loose loads.





Dropper posts make mounting / dismounting or waiting at the lights a breeze, and also open up the versatility for families with different sized pilots.    The Tern GSD and bikes like it have a post in a post to offer similar versatility.



The Surly Big Dummy comes with two massive pannier bags which will certainly be used down the line.  The initial brief was a car-replacement / kid carrier.   The one thing that this bike really needs is the new Surly Double Kickstand which dropped the same day I finished this build.    It’ll be the first thing to be added giving much needed stability when loading super precious cargo.




If you see TOM around town, give him a honk / wave!  

  • Frame: Surly Big Dummy - Medium
  • Fork:  Surly 
  • Headset: Cane Creek
  • Rims: OE
  • Hubs: Novatec
  • Shifters: MicroSHIFT Advent
  • Crankset: CYC 175mm
  • Motor: CYC Photon - 750w / 110nm
  • Display: SW102 Display
  • Battery: 48 V / 17 AH battery, 
  • Chainring:  38t Narrow-wide
  • Rear derailleur: MicroSHIFT Advent 11
  • Cassette: Microshift Advent 11-46t
  • Chain: KMC
  • Brakes: Zitto
  • Tyres: 26x2.5 Surly Extraterrestrial
  • Handlebar: Loop bars 31.8
  • Stem: Kalloy 
  • Seatpost: Brand X Ascend II 150mm
  • Cages: Blackburn
  • Front rack: Blackburn Local Basket
  • Grips: ODI Lock on Grips
  • Saddle: Selle Italia X-Base
  • Pedals: Zitto
  • Extras: Blackburn Outpost Frame bag, Quad Lock Wireless Head and Outfront Pro mount, SKS Blumel 75 Fenders, Front / Rear Lights, Nice Bike Bell, TOM number plate.


I got my CYC Photon from Melbourne Powered.  You can also get them directly from CYC Motor or your local distributor.

Want FYXO to build one for you?  Get in touch