CV (Constantly Variable) Transmission For Bikes

I received the following email from an inventor in Switzerland who is working on CV transmission for bikes. This would do away with front and rear mechs and the gearing would all be built into the single chainring which would “change size” at the push of a button. Sounds interesting, but I wonder if it will ever come to market. Anyway, here’s his email, there’s a link to survey that he’d like you to complete if you have the time. Thanks.


I am a passionate cyclist and inventor from the Business School of Lausanne in Switzerland.

I am currently working on a variable diameter gear for road bicycles. To bring the idea to reality I need to perform some industry analysis and I would therefore greatly appreciate it if as many as possible road cycling club members could complete to following survey ( It should take approximately 10 minutes to complete. Please feel free to send it other road cycling clubs and/or friends.

The survey contains more information on the product idea and the key benefits the variable diameter gear will offer. Here is a brief outline however:


1) The VD system will cover the entire gear ratio range offered by other manufacturers, without the need to manually change the chain rings and/or cassette. A standard drivetrain from other manufacturers typically consists of a 53-39 chain ring and a 11-28 cassette. The VD system will be the equivalent of riding a 55-34 by 11-32. With the VD system, a cyclist will be more likely to find a comfortable gear for different types of terrain (climbs, flats and descents).
2) When changing gear on a current product, there is usually a big jump in the gear ratio (e.g. changing from the big chain ring (53) to the small chain ring (39)). With the VD system, a cyclist will be able to change the diameter of the gear all the way from its smallest possible size to its largest possible size in small increments (e.g. 34-35-36…53-54-55). This will allow a cyclist to change from one gear to another without a big change in pedalling speed/cadence and to also precisely select the most comfortable gear.
3) The system will be able to change gear 100% smoothly, regardless of how hard a cyclist is pushing on the pedals. A cyclist will be able to change gear during sprints, without the concern of the chain jumping, falling off or hearing “crunching” noises.
4) Gear changes will be silent (other cyclists will not be able to listen and anticipate a gear change during competition for example).
5) The system will require close to no maintenance or calibration (e.g. adjustment of derailleur).
6) The system will take about half the time to install.

How it will work:

Currently, most road bicycles have 2 or 3 chain rings and a 10 or 11 size cassette. A user can change gears by pressing on a combination of levers, from where a front and rear derailleur moves the chain from one gear to another. This change of gear provides a cyclist with different gear ratios for different terrain (climbs, flats and descents). The VD gear being proposed will work differently. The product will have one gear at the back and another single gear in the front. The front gear however is capable of changing diameter. A user will push one button to make the gear bigger and another button to make the gear smaller. The change in the size of the gear will provide a cyclist with different gear ratios for different terrain. The system will have no front and rear derailleur.

Thank you very much,

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