Doppio CX

The 2-speed bottom bracket gearbox “Doppio” from Kappstein is a compact, light and comfortable transmission unit in the bottom bracket bearing. Thanks to the extremely compact design, the entire gearbox is only 1cm wide and only about 200g heavier than conventional bottom brackets. The Doppio offers the driver a ratio of 1.57 in the heavier 2nd gear. This allows the number of gears to be increased with many possible combinations.

Thanks to the compatibility with any conventional BSA/BSC bottom bracket with a width of 68/73mm, a wide range of possibilities becomes available for use. A patented bolting system enables problem-free installation without any processing of the frame. The main area of application for this transmission is in urban and city areas, but the Doppio can also play to its strengths in e-bikes in conjunction with a rear engine. Usage as a pure 2-speed system or in combination with hub gear systems is also a practical option.

Single-speed - Doppio

It is also possible to use the Doppio as a single-speed version. This option uses only the heavier gear with a ratio of 1.57. With a mounted 32t chainring this corresponds to a number of about 50 teeth. The switching device, shift cables and shifter are not necessary in this case and are eliminated.

But what's the use of it? Quite simple, for those who need a heavier gear / transformation ratio but can not or do not want to use a huge chainring. Not infrequently bicycle frames are not designed for large chainrings. There are also special bikes such as callapsible bikes that have to be foldable on the one hand, and on the other hand designed to save space. The sleek and compact design of the single-speed-Doppio ensures a pleasing look and is a weight-saving solution for very special types of bicycles.

The gear transmission is controlled by a Bowden cable with the help of a small lever on the handlebar. The shifter is hardly noticeable and fits perfectly into a tidy handlebar set-up. The Bowden cable on the gearbox is fixed with an innovative clamping mechanism specially developed for the Doppio.


Number of gears: 2
Drivetrain: belt/chain
Gear ratio: 1 : 1,57
Chainline: 43,5mm
Q-factor: 185mm
Bolt circle diameter: 4 x 104mm
Weight: set 1250g
Crank: Kappstein JIS square
Crank lenght: 175mm
Switching operation: bowden cable
Switch unit: Kappstein 2-speed Shifter
Chainring: Kappstein 32T
Bottom bracket mounting: BSA/BSC
6 CNC-shaped planetary gears
Application field: urban, e-bike, city, trekking



The planetary gear inside the Doppio

Availability & references

The Doppio CX is currently only available for OEMs and dealers. With Ghost, we already have a well-known manufacturer on our side who will offer the Doppio with the premium version of the “Ghost Square Times 9.9 AL”, starting with the 2018 models. Our partners of Logo E-Bikes also use the Doppio in their model XD02, a stylish, comfortable and comparatively lightweight urban bike with rear-wheel drive and integrated battery.

The Doppio is currently not offered in our online shop as it will only be sold via exclusive dealers. For those who want to retrofit the Doppio on their bike, we will connect with a bicycle dealer nearby. Just contact us with the appropriate information about your place of residence via e-mail. We are currently looking for competent bicycle dealers throughout Germany in order to build up a joint dealer network with them. The Doppio can then be purchased from these exclusive dealers and installed directly by specialists. Further information about the selected dealers and the price will follow shortly.