Posted on June 20, 2022 by Ron Frazelle
If you have a rear disc brake on your current steed, you can now turn that bike into an electric bike! That’s right! Skarper claims that with zero modifications to your frame and/or wheels, you can have your favorite bike transformed into an E-bike.
Photo: Skarper Technology. Replace your current rotor with the Skarper “DiskDrive” for an instant e-bike
According to Skarper, all you need to do is swap your current rotor for their proprietary “DiskDrive” rotor and it will transform your current bike into an e-bike, without compromising the rear braking ability. In all fairness, this sounds a lot like the premise of the Bimotal Elevate system… just not as powerful. While the Bimotal system offers a 750w motor, the Skarper is rated to 250W. However, the Skarper system is pretty much self contained without any wires stretching to a battery that will occupy a bottle cage.
Skarper also seems to have the added benefit of being compatible with flat mount brakes, and frames where the caliper is tucked inside the stays. Because of that, it seems like it has the potential to work with many more bikes than the Bimotal system (though Bimotal claims to be developing flat mount compatibility as well).
It’s worth noting that neither option is actually available for purchase yet, so it will be interesting to see which one delivers first.
Here is what they say: “Skarper has engineered a full gearbox into the space of a rear disk brake. When not electrically driven, the disk behaves exactly as a normal disk without any compromise on performance or function. Your bike is ready for an electric drive at any moment. Precision features on the disk allow the direct connection of a Skarper motor drive unit whenever desired.”
Photo: Skarper Technology Skarper Drive Unit attaches to the disc side chainstay.
“A state-of-the-art electronic drive system has been integrated into a compact drive unit. High capacity Lithium cells provide class-leading range and weight*. A high torque brushless motor provides smooth power delivery to tackle any urban terrain. The drive unit has been engineered to click onto the DiskDrive™ to instantly transform your bike into the ultimate e-bike.”
*We’re not exactly sure what “class” they’re considering, but we’d assume the Bimotal system would be included. In that case, the Bimotal system claims to be lighter at 2.7kg vs. 3kg, and includes a slightly larger capacity battery at 250Wh.
“To provide all the power you need whilst remaining energy efficient we developed DynamicClimb™ – a bespoke algorithm using a suite of wireless sensors, that measures the rider’s output, road incline and monitors drive unit parameters thousands of times a second. DynamicClimb™ delivers a smooth and powerful ride. Whether it’s accelerating ahead of traffic at a red light, or climbing that steep hill on the way home – DynamicClimb™ will provide the power you need.”
Torque: 50 Nm Motor: 250W rated Weight: 3 kg + 300g for DiskDrive rotor Battery Wh: 202wh Charge from empty to full: Range: Up to 60 km Drive Type: DiskDrive™ Top speed: 32km/h (restricted to 25km/h in relevant countries) Range on 30 min charge: 15-20 km
Pricing hasn’t been releases for this product on their website. But, you can be notified when they are available for purchase here.
Ron Frazelle is the Cycling Lifestyle Editor for Bikerumor, he has been writing about bicycles and the cycling way of life for 7+ years. Prior to Bikerumor, he worked in the bicycle industry, living and breathing bicycles since 1995. He is based in Anaheim, California, Frazelle is an avid cyclist of all disciplines, camper, father to 6 children, husband, musician and self-proclaimed retro-grouch.
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I’m guessing most frame manufacturers will say this voids warranty. 250w seems like a lot of torque and point loading on the stay in direction it wasn’t designed.
250W is meaningless. It is the torque that will ordinarily destroy things before super high rpms and the torque will be tiny with respect to the weight of the rider. Much more powerful Hub-motors are used with out issue and they seem much better than this contraption.
True, but it would still likely void most manufacturers frame warranties
The forces of braking are a lot higher and over a shorter arm.
Gads I wish the industry would find a way around wattage. You can have a 5k watt system that doesn’t exert the strain on your frame that this system does (BTW, they do exist). Torque is real, usable power. Wattage is basically top speed. Either way, even the most casual rider exerts far more than 250 watts and 50nm’s of torque with just one leg, on every ride (not constantly, but neither does this system). I exert more than 90nm’s of torque with one arm, on wrenches in my shop daily and I am 66, fat and haven’t exercised, except to bike commute, in five years.
No, this doesn’t convert “any” bike. Not all bikes have a disc brake. Get your article titles correct and stop misleading readers.
On the contrary, this kit does not require a rear disc brake, just a rear wheel with a disc rotor. That can be found for most any bike, including one with a rim that has a machined brake track for existing rim brakes.
Love how ANY is in caps but the first sentence is “If you h e a rear disc brake”
im so excited. my tarmac disc i gonna be sweet
its good for 9 to 11 miles??/ what the hell good is that.
Good for the target market that’s likely to buy such a thing.. ? Most casual bikers aren’t doing many miles…
60Km on full charge it says.
It doesn’t compromise rear braking ability… It merely compromises frame safety.
Applying forces to the mid-section of a tube that wasn’t designed for external forces being applied to it.
Every (larger) brand’s design criteria for new bikes is being able to suspend the riders weight on vertical surfaces, that includes chainstays.
And that maximum 30kg is far within that.
Putting this on my Aethos.
I like the looks and concept of this contraption. Can it deliver? We’ll see if this i marketing hype or real.
How much of a pain is it to swap a tube? This is best aimed at commuters as recreational cyclists will want more range and hill climbing torque. If I can’t easily swap a tube on my way to work, it is worthless.
Watching the video. It looks like the whole unit clips in and out. Doesn’t seem like tube swaps will be an issue at all.
I think things like this are sort of interesting, but I wish folks wouldn’t hawk them before they reach the market. Odds are ot will cost too much for what it can deliver. 50nm’s of torque is plenty, bit not if the unit amd its mount absorb most of it (which I suspect). Then there is the hassle of changing a tube (the bane of all hub drives). What about control? Most supposedly intuitive systems make all riders ride the same.
I like the idea of modular ebike systems. There’s already some on on the market that let you yank out the battery and drive motor to save weight when you don’t need it. With the Skarper system, I’d like to see an easily replaceable battery
The battery is easily replaceable, so that it is future proofed for the anticipated improvements in battery technology.
There is a lot of speculation in the comments regarding the chainstay reaction force damaging the frame, so allow me to explain using science in place of speculation!! The specs define max torque as 50 Newton meters, and the chainstay clamp appears to be ~8 inches from the wheel axle, so: 50 Newtons = 11.24 pounds force, and 8 inches = 8/39.37 = 0.2 Meter. Therefore 50 NM would apply a maximum of 11.24/0.2 = 56 pounds force to the clamping location on the chainstay. As others have correctly stated, braking reaction forces applied easily exceed this force, with much greater regularity.
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