Hidden motors for road bikes exist — here’s how they work

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The UCI made headlines back in March for checking several dozen bikes for hidden motors at Milan-San Remo. Many fans laughed off the incident as a ridiculous waste of time, somewhat prematurely perhaps. Concealing a motor in the frame of a road bike isn’t just possible, there are products on the market already that cater specifically to this purpose.


CyclingTips editor Matt de Neef visited the Australian distributor of an e-bike motor brand to learn more about the technology and test ride a bike with a concealed motor.


Warren Anderson visited Eurobike last year to check out the vast array of electric bikes on display. In the process he became the Australian distributor for vivax Assist, an Austrian-based e-bike company that sells, among other things, crank-drive motors that can be hidden inside the seat tube of a road or mountain bike.

The e-bike business is a bit of a passion project for Warren — he’s retired now, having made a living as the owner of a local Australian spa company. He was good enough to take time out of his day to show CyclingTips the vivax Assist.

The set up

The basic vivax Assist package costs in the vicinity of AUD $4,300 and comes with a battery pack, a saddle bag for housing the battery, a charger, a seatpost for housing an electronic control unit, the motor itself and the adapters necessary to connect the motor to the crankshaft of the bike.

The motor, which measures 22cm in length, is fed into the seat tube and connects with the crankshaft via an interlocking gear — the gear on the bottom of the motor locks in to a gear ring which is placed over the crankshaft.

kurbel_mit_motor_gradient_gro

The motor is connected to a battery pack via the electronic control unit housed in the seatpost provided. By default the battery lives in a saddlebag, but it can also be concealed in a bidon seated in the seatpost bidon cage (more on that in a moment).

A simple button to start and stop the motor is then mounted on the underside of the handlebars and routed to the control unit in the seat post.

The Vivax assist motor is rated at 200 watts (the maximum for e-bikes in Australia is 250W, beyond which they are classified as motorbikes) but in reality, we were told, the unit provides somewhere in the vicinity of 110W to the driveshaft. This is in addition to whatever the rider is pushing through the pedals.

There are two main battery options available: one that provides a total of 60 minutes of power assist and one that provides 90 minutes. The motor weighs 750g, the 60-minute battery accounts for 900g and the total package is 1.8kg. For the 90-minute battery option you’re looking at an extra 400g.

The setup requires Shimano Hollowtech II cranks and is compatible with any frame that has a straight seat tube with enough room for the motor, which measures 31.6 mm in diameter.

The motor is 220mm long and 31.6mm in diameter.
The motor itself.

Installation is reportedly a tricky affair and likely to be challenging for your average mechanic. That said, Warren had his vivax Assist installed at his local bike shop.

The build

To demonstrate the vivax Assist Warren had a regular-looking race bike built up. The frameset was a full carbon Vivax-branded number, reportedly hand-crafted in Italy and built up with a Shimano Ultegra groupset; 3T bars and stem; a Selle Italia Carbonia SLR saddle; Zipp 60 clinchers and bidon cage; Look pedals; and, of course, the vivax Assist package. The whole bike, with pedals, weighed 7.9kg.

Looking at the bike there are only a few things that announce the fact that it’s not a standard road bike: the wire running underneath the top tube to the prominently placed start/stop button is one, as too is a saddlebag with vivax Assist emblazoned on it. The seat tube also had a few extra clamps around it than you’d normally see and there’s a tiny pin, low down on the non-drive-side of the seat tube, to hold the motor in place inside the frame.

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Nearly all of these distinguishing features can be done away with, however, by purchasing vivax Assist’s “Invisible Performance Package”.

Making it invisible

For an extra €499 (roughly AUD $700) the Invisible Performance Package allows you to “invisibly transform your racing bike into an e-racing cycle”.

The saddlebag battery is replaced by a “bottle battery” lasting 60 minutes and presumably connected to the motor via the seatpost bidon-cage mounting holes. The wired, start-stop button is replaced by a wireless option which can be positioned at the end of the handlebar drops or, according to the product literature, “anywhere you like”. Warren suggested mounting it under the saddle to keep it hidden.

Riding the bike

Activating the vivax Assist motor is a simple case of turning the pedals and then pressing the start/stop button. The motor kicks in after roughly a second or so.

The motor doesn’t create any extra resistance in the drivechain when you’re riding with the motor disengaged; it feels just like you’re riding a normal bike. But when you press the button, the power that you’re pushing through the bike is supplemented by what feels like roughly 100 watts.

To disengage the motor you simply stop pedalling. You get a little bit of a jolt forwards from the pedals, similar to what you might get when you’re riding a fixed-gear bike for the first time and you forget you shouldn’t stop pedalling. Except in the case of the vivax Assist, the impetus from the motor stops immediately after that initial jolt, and you can then freewheel as normal.

The motor certainly made a difference when riding the bike on a reasonably steep climb. It certainly didn’t feel like the motor was doing all of the work, but the extra power made it noticeably easier to maintain the current pace while providing inspiration to use the power saved to push harder.

The motor does make a little bit of noise but it’s not as loud as the end of the above video might suggest — in that case the microphone was placed close to the bottom bracket. When riding along it is only slightly audible over road and wind noise.

Could hidden motors be used in the peloton?

The vivax Assist has been designed with the recreational market in mind, to “balance out the performance difference between riding partners” while ensuring “the bike’s aesthetics and an authentic feeling ride are preserved”. Warren Anderson told CyclingTips that he expected the system to be of particular interest to female riders who are looking for a bit of helping keeping up with their male training partners.

But despite being designed for the recreational market, the key question here is: could the vivax Assist or a product like it be used in the professional peloton? The answer in our opinion is a resounding “yes”.

Considering the vivax Assist with added Invisible Performance Package, there are only a few minor issues that would make it obvious, without looking specifically, that a motor was being used: the presence of the seat tube pin, the placement of the start-stop button and the noise the motor makes.

The first of those issues could conceivably be addressed by a well-placed manufacturer’s sticker or other adornment. Other similar brands might also have a design that doesn’t require a locking pin. Hiding the button could conceivably be achieved by the careful and creative use of bartape. Something along these lines, perhaps:

Noise from the motor could theoretically be dampened by the use of insulating materials inside the frame. But arguably the sound wouldn’t need to be dampened at all.

A product like this wouldn’t need to be used throughout an entire race, or even for anything length of time. It might only need to be engaged once or twice — when attacking on a climb or cobbled sector, for instance, and trying to create a defendable lead.

Think of a climb like the Oude Kwaremont at the Tour of Flanders, a cobbled sector like the Carrefour de l’Arbre at Paris-Roubaix, or a summit finish on Alpe d’Huez. All come at a decisive time of the race, all are lined with fans, and all are therefore very loud. The noise of an in-bike motor would be virtually impossible to detect.

It’s also worth considering that the vivax Assist is just one example of this technology; a product that’s available to the everyday consumer. It seems reasonable to expect that there are similar products that aren’t publicly available, that could be customised to negate the tell-tale signs mentioned above, thereby avoiding detection altogether.

It seems clear that it is technically possible to have an effective motor hidden inside the frame of a road bike. Whether any riders, past or present, have used this technology during races remains to be seen, but the fact the UCI is taking this issue seriously should be taken into account.

It’s hard to imagine the sport’s governing body investing considerable time and money inspecting frames for motors if they don’t believe they have a very good reason to do so.

CyclingTips would like to thank Warren Anderson for his time. If you are interested in the vivax Assist — for recreational purposes, of course — and you’re in Australia, contact Warren for more information. You can also find more information at the vivax Assist website.

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