The Schlumpf gearbox is an ultra-flat planetary gearbox located on the right between the bottom bracket and chainring. The Schlumpf gearbox is shifted by a kick with the heel on a slightly protruding gear knob on the bottom bracket axle.
The Speed Drive gearbox used by Stromer provides a 1.65-fold speed ratio for all gears at the push of a button. This means that all gears of a rear derailleur, whether derailleur or hub gears, are translated 1.65 times into fast gears. The Speed-Drive is therefore not simply "one more gear" but a significant increase in the number of gears, whereby, in contrast to the Mountain- and High-Speed-Drive, there may be overlaps due to the smaller ratio jump.
You can also imagine the effect as follows: If a 34-tooth chainring is fitted at the front, it turns 1.65 times faster at the push of a button, i.e. the effect is the same as if the chain were thrown onto a 1.65-tooth larger chainring, which would correspond to a chainring with 54 teeth!
Conversely, it is possible, e.g. at a stop, to change the overall gear ratio from "large to small" with a light tap on the pedal crank, e.g. to be able to start off more easily.
In fast driving mode, operation via "kick" is rather borderline and only recommended for experienced drivers.
Links
If you want to find out more about the Schlumpgetriben, we recommend the following links:
- smurf.ch (general info)
- smurf.ch (FAQ)
- stromerforum.ch (thread)
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