eMTBs with Integrated Gearboxes are Here

I’ve heard some rumblings from industry insiders in recent months about disruptive technologies on the horizon. These sometimes come across as worries about the future of mountain biking, and are often aimed at innovation coming from China. After a few Euro Bike reveals, we may be getting an inkling about what has been keeping manufacturers of traditional mountain bikes, and drivetrains in particular, up at night.

The news coming out of Eurobike is even more disruptive than the Avinox Apocalypse from Sea Otter. If you are not into eMTBs, this news is not for you – at least not yet. If you are, this could represent a revolution. Two prominent manufacturers of eMTB drive units, Goboa and Avinox, were showing all-in-one drive/transmission combos for performance eMTBs. These aren’t conventional transmissions with gears that have gaps between them; they are continuously variable transmissions (CVT) that seamlessly move between ratios with no loss of power. You will be able to program gears into the system for a more conventional approach or use full automatic, choosing a cadence or perhaps a profile that is the most efficient or the most powerful. Based on your presets, speed, cadence and likely angle of climb or descent, the electronic controller will decide the optimum ratio and give it to you instantly. These aren’t regular CVTs; these are electronic CVTs, straight out of a ’97 Prius.

What is a CVT?

Most hybrid cars use an eCVT to deal with both electric and gas-powered engines. The concept is simple, and the execution in vehicles is quite elegant. Earlier gas-powered vehicles with mechanical CVTs weren’t so elegant, but examining how they worked will help us understand what’s going on here. These first CVTs involved two pulleys joined by a belt, one driven by the motor and the other connected to the drivetrain. The easiest way to think about these is that each pulley has a variable diameter that grows or shrinks as necessary based on the circumstances,* changing the gear ratio seamlessly and without any steps and keeping the vehicle’s RPMs at an optimal level, either for power or efficiency. The pulleys work in concert in order to keep the belt tensioned. While one pulley is increasing in diameter, the other decreases by the same amount. If you think about one pulley being the chainring and the other being a single cog, that should give you the idea.

*Another way is to imagine two cones parallel to each other but with points facing the opposite way, moving in and out in opposite directions

Issues with Mechanical CVTs

This system, implemented in cars like the Subaru Justy worked, but it was clunky and prone to failure, and there were significant energy losses due to friction. Worse, there was a nasty lag between throttle engagement and any change in speed. I imagine the accelerator felt like stepping into a bowl of Jell-O. The system ran very hot, and even the engine sound was terrible.

Fortunately for eMTB riders, Toyota solved all of those problems using a planetary gear and two electric motors to accomplish the same task. There is very little friction in the system or energy loss, and little to no maintenance required. I owned two different Toyota Highlander Hybrids with eCVTs, and both worked flawlessly.

It seems several companies are working on eCVTs that may soon see production, but Gobao may be out front for the moment in terms of implementation in performance eMTBs. The company notably makes Aventon’s motors, but they haven’t made much of a splash in the eMTB sphere otherwise, at least not until now. At Eurobike, Gobao was showing the first rideable prototypes of bikes with an integrated, electronic, continuously variable transmission (eCVT). It charges incredibly quickly, will deliver 150 Nm/1500w peak power, like the new Avinox M2S, and there were rideable examples spinning around parking lots at Eurobike. Avinox has one in the works as well, their MG unit, which several brands showed at Eurobike as displays on bikes or frames, but I have yet to hear that any were rideable by journalists. While Gobao are making a big splash right now, they weren’t the first to employ an eCTV in bikes. In fact, there have been bikes on the market using this system for almost three years.

Owuru, whose largest shareholder is Decathlon Bikes, were the first to market. While they do make a couple of eMTBs, they aren’t aimed at the performance market, and perhaps as a result, they flew under the radar. After ten years of development, Decathlon e-bikes with eCVT-equipped drive units from Owuru have been available to consumers since late 2023. Owuru’s* co-founder, Christophe Deleval, came from the automotive industry and was inspired by the eCTV system found in the original Toyota Prius. He sought to scale it down to work with e-bike drive units and to be contained within the housing. So this big news we are hearing about now isn’t so new, but it’s the first time it’s been designed for high-performance eMTBs, which is why everyone is suddenly taking notice.

*At that time, Owuru was known as E2 Drives

So while Gobao and Avinox’s systems are aimed at a different market, it seems very likely they have reverse-engineered the Owuru system, which copied Toyota’s Prius system. These eCVTs can be used in different ways on bikes. You can use predetermined steps between gears, but the shifts will be seamless because there are an infinite number of ratios between each gear. It would be like having a cassette that is a smooth cone with a chain that glides up and down, stopping at any point. There will be no clunk or grind from a chain moving from one cog to another, and no interruption in power output. Owuru’s bikes have been criticized for omitting a manual mode, but neither Avinox nor Gobao is likely to make that mistake. Whether riders will use the manual mode, like the rarely tapped paddles in an automatic car, remains to be seen.

What Avinox Says About their MG Drive Unit

• Smooth gear shifting: Promising uninterrupted power delivery and a shift time of less than 0.1 second, the MG Concept supports shifting during high-torque pedaling as well as while stationary.
• Fully customizable gear shifting: Riders have many options. They can shift one gear at a time or multiple gears at once, and can opt to shift gears manually or automatically with cadence-based auto mode or AI+ auto mode for speed riding.
• Little to no maintenance: The internal derailleur unit requires no maintenance during its lifespan, while the use of a single-speed chain or belt eliminates the need for a rear derailleur or multi-speed cassette.
• Smaller and lighter platform for all e-bike types: Adopting a completely new system design, the new platform’s drive units can be easily adapted to eMTB, eTrekking, eSUV, eGravel and other bike models.
• Natural riding: Riders with equipment and load over 150kg won’t feel any spongy feeling
• Intelligent anti-theft technology: The new system offers real-time locking of the motor and use of the anti-theft function even without power

The Status Quo

It can’t be good news for SRAM or Shimano to possibly be on the cusp of losing drivetrain business in the fastest-growing, most premium market in the mountain biking world. It seems likely that many eMTBs will continue to use conventional drivetrains, but it seems even likelier that the top end will banish derailleurs for good. The forecasters at both of those companies will certainly know about this disruption, and it’s possible they are working on their own drive units using eCVTs. I’d be surprised if every drive unit manufacturer wasn’t chasing the same bone; Bosch, Specialized (Brose), Yamaha and even smaller players. It will be interesting to see if TQ can adapt their system for an eCVT, considering their motor runs in line with the bottom bracket.

These companies are already off the back, but that doesn’t necessarily mean their response will be subpar. More competition in the drive unit market can only be a good thing for consumers, and it’s probably about time some of the big companies, in both drives and drivetrains, have stiffer competition, considering how often there have been near-monopolies in the drivetrain market in particular.

Likely the worst part of this evolution for component and bicycle manufacturers alike, aside from lost revenue, is giving up control. Bike companies love using drivetrains as separators at various price points and both Shimano and SRAM rub their hands together about the prospect of selling entire groups for eMTBs, that require more robust and expensive versions of everything. It may not be the apocalypse, but larger bike companies, whose names are curiously absent from Avinox’s list, will be plotting to get back to the top. Locally, DJI-equipped bikes are flying out the doors, and everyone I know who has bought a new eMTB in the last couple of months is on one.

Why Does This Matter?

MTB pundits on the web have been screaming for lighter and more efficient gearboxes for bikes since Internet Explorer was a thing. For most riders, the weight and energy lost to friction are deal-breakers, but the benefits are clear. Eliminating a derailleur, cassette and chain reduces and centres weight, while lowering maintenance, repairs and unsprung weight at the end of the swingarm. Aside from the Forbidden shown above and a few others, the prototypes shown at Eurobike used Gates belt drives, which last at least three times as long as a chain and cassette, require very little maintenance, and are almost silent in use.

Because of all the power and torque produced by eMTB drive units, a little energy lost to a gearbox shouldn’t be a big deal. The belt is a little less efficient than a new and clean chain, but in real-world situations, where chains are rarely new and even more rarely clean, the difference ends up being only a few percent, which will be easily made up by the motor. It’s hard to imagine any new eMTBs using conventional drivetrains in the near future.

I’m particularly interested to see Bosch’s response to these developments, considering they are a massive supplier of components for automobile transmissions, including electronic and electromechanical systems for eCTVs found in production vehicles.

Buckle up, ladies and gentlemen, we’re about to hit some turbulence.