It would be easy to pigeonhole the new Skarper DiskDrive Ebike Drive System as simply another electric bike conversion kit, but Skarper’s approach is the first of its kind.
The Skarper system eliminates the complications of a one-way conversion kit, by containing everything within a compact unit, using a patented design to drive your bike's rear wheel.
The unit contains the electric bike motor, 'brain' and battery cells, housed in a compact case that mounts on the chainstay. The rotor stays on your bike, but the main unit simply clicks on and off in seconds.
The Skarper DiskDrive Ebike Drive System is priced at £1,495, including the Skarper motor unit, Bluetooth cadence sensor and DiskDrive rotor.
Skarper DiskDrive Ebike Drive System – how does it work?
For context, most of the best ebike conversion kits, from the likes of Swytch, Cytronex and Boost, are one-way – they require switching out a wheel and adding cables, batteries and fittings.
This means, as good as these conversion kits can be, you’d be very unlikely to revert your bike back to ‘just’ pedal power.
The Skarper system has a full gearbox integrated into its DiskDrive disc rotor. The gearbox has been integrated cleverly into the space between the hub and the disc-brake surface in collaboration with Red Bull Advanced Technologies – a real engineering accomplishment.
The fully sealed rotor is the heart of the Skarper technology and connects to the Skarper Drive Unit with a lever-actuated bayonet fitting.
Once mounted, a drive shaft from the drive unit transmits power to the DiskDrive rotor, which in turn drives the rear wheel. The drive unit houses the motor, battery and control electronics.
The reason the Skarper Drive Unit drives the bicycle forward is because the chainstay of the bike is immovable, forming a solid platform and essentially creating a 'torque arm' effect.
Skarper says very little force is put on the chainstay of the bicycle, which in any event, is designed to take significantly higher forces under normal braking loads.
The system is controlled by a cadence sensor attached to the left-hand crank of the bicycle. The cadence sensor is very sensitive and designed so there is no lag in acceleration when you start riding.
This is especially good when having to start on a steep hill.
In addition, Skarper has developed an incline sensor algorithm called Dynamic Climb. This essentially senses when you're on an incline (plus the severity) and automatically adjusts the power needed for you to enjoy a smooth and controlled ascent.
This means you do not need to switch modes to add power when climbing.
The Skarper unit conforms to the European and UK-mandated 25kph (15.5mph) cut-off regulations. When the cut-off is reached, your bike will ride as a non-assisted bike when travelling in excess of 25kph.
Skarper DiskDrive Ebike Drive System setup
After riding the initial Skarper prototype and a newer incarnation, I now have the final production version, barring the rubber charge port cover (my test unit has a 3D-printed version).
Fitting the Skarper from scratch is incredibly simple – you start by removing your existing disc rotor and replacing it with the DiskDrive rotor, which fits using a standard lockring.
You then attach the T-shaped ‘stud’ to the chainstay and offer up the Skarper unit, aligning the motor pin and locators with the slots on the rotor. The drive unit slots into a lock on the chainstay stud and is locked using a half-moon-shaped handle.
Finally, you install the silicone-encased cadence sensor onto the crank arm and you're good to ride.
The bike and Skarper system combined to create an 11.4kg ebike (the Black Series Multistrada gravel bike I tested it on included pedals and 40mm gravel tyres, weighing in at 7.9kg).
It’s an impressively light package considering the £11,800 Wilier Filante Hybrid (with road tyres and Shimano Dura-Ace Di2 R9200) hits the scales at 10.74kg.
The Skarper’s three power modes follow a similar format to standard electric bikes. The Skarper, however, doesn’t have a remote control with a battery indicator – that accessory will come later in the year, along with a free phone app that’s in the late stages of development.
It needs it, too, because the design's battery-level ring light is nigh-on impossible to see when you ride – you can only glimpse it when stopped at traffic lights.
The unit already contains communication hardware encompassing Bluetooth, ANT+, and WiFi.
Skarper DiskDrive Ebike Drive System specifications in brief
• 250W-rated motor, 45Nm (UK/EU legal maximum, US specification imminent)
• Weight: 3.9kg unit + 620g rotor
• 240Wh battery
• 2.5hrs charge time
• Claimed range: Up to 50km (Eco) assisted in city conditions and 70km achieved in out-of-city road-cycling conditions. Up to 30km in turbo mode.
• A 30-minute quick charge gives a range of 10-15km
• £1,495 including Skarper motor unit, Bluetooth cadence sensor, DiskDrive rotor
Skarper DiskDrive Ebike Drive System ride impressions
Initially, I thought that not being able to shift modes on the fly would be an issue, but with the supremely clever Dynamic Climb programming, I found riding in ‘eco’ mode was more than ample, because it’s a light bike.
Hit a climb and the Skarper’s programming takes hold and builds the power slowly, making it a rewarding experience to climb with. All the time, I was aware I was riding a light bike.
I rode the Skarper back-to-back against a rear-hub motor equipped electric gravel bike as part of my testing, and the Skarper’s power was every inch its equal. The smart delivery of the power as the angle of the climb changes is revelatory in comparison.
With ‘only’ a 240Wh battery capacity, I expected a low range, but much like super-light, expensive electric road bikes with small internal batteries, that was somewhat unfounded.
That’s because, on a standard non-assisted road bike, you’ll spend most of your time above the EU 25kph/15.5mph limit, hence you aren’t using the battery. The DiskDrive rotor has a built-in freewheel, so when the motor isn’t running there’s no drag on the system.
Skarper also has built-in clever control, in that when you don’t require motor assistance, pedalling backwards a couple of revolutions will sleep the motor. Approach the foot of a hill and backpedal again, and it springs back into life.
The Skarper will find most use in urban commuting, where you can simply click the system onto your existing commuter bike with little effort. Take it off and your bike is just as it should be, barring the small weight penalty of the rotor, which performs its task like any other rotor.
I, however, wanted to try the unit out in more diverse terrain, hence fitting it to a gravel bike.
On tougher gravelly surfaces, the system’s stability impressed – locked into the rotor and supported by the T-shaped stud on the chainstay, the unit was free of rattles and shakes. Rocky, dry, fast descents, rutted tracks, roots – and even the occasional bit of air time – didn’t upset the unit.
As a result, I’m convinced the Skarper will not be unseated in regular ‘urban’ use.
The range it achieved on a pure gravel ride over the rocky, chalky byways and trails of the Wylye Valley impressed. The unit achieved 71.5km/44.4 miles, with 885m/2,903ft of ascent. On a purely road test ride, that rose to 90km/55.86 miles, with 991m/3,252ft of climbing.
In my experience, the range is easily a match for ebikes equipped with Mahle’s X20 motor and the smaller-battery option, along with Mahle’s X35+, Fazua systems, Kynamic’s hub-motor system, and even Bosch’s SX lightweight options.
The Skarper charges inside two and a half hours, with a quick 30-minute charge giving you 10-15km.
Compared to existing conversion kits, the Skarper system is more expensive at £1,495. The Cytronex kit comes in at around £1,000, depending on specifications. Swytch’s equivalent-range Go++ kit is £849, and Boost’s kit starts from £649.
Each of those rivals requires the building of a wheel and they can only be used on one bike. With the Skarper, you can purchase additional rotors – and therefore use the Skarper motor across multiple bikes.
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Skarper DiskDrive Ebike Drive System bottom line
The Skarper DiskDrive Ebike Drive system is unlike anything that has come before it.
It’s classified as a conversion kit, but that does the Skarper system a huge disservice, in many ways.
If anything, the Skarper is an accessory, in that it’s as quick to fit as a set of bike lights. For most conversions, you will never convert back to a regular bike, but the genius of this clip-on system is that your bike stays almost standard until you want pedal assistance.
Is it perfect? No. It needs a bar remote with a battery indicator, and a phone app to collect data, tune settings and give accurate battery information – although both are in the works.
The initial kit is expensive too, but it just fits to your bike, and if you want to add electric assistance to another bike in your household, it's just a case of buying a second rotor.
I like the thought of riding my best bike to work during the week, then unclipping the Skarper come Friday night and having my own unassisted bike to ride at the weekend.
Skarper might just have created a product that could change the way we approach ebikes forever.
Product
| Brand | 4080 |
| Price | 1495.00 GBP |
| Weight | 3.9000, KILOGRAM () - |
