Doppio Gear Box

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 collapsable 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.