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The Schlumpf Speed-Drive takes an existing drivetrain and gears it all up by 60% when needed. This makes a 35-tooth (35T) chainring feel like a 56-tooth (56T) chainring.

It gives you higher gearing for higher speeds.

All of this happens with no shifter, no shift-cables, no shift-cable housing, and no barrel-adjusters.

Instead, you switch gears by kicking a button from side to side on your bottom-bracket spindle.

The most common conformation of a Schlumpf SpeedDrive is with a 110bcd five-arm spider, but other chainring systems are available if this just won't work for you.

The drive is held in place with 45-degree chamfered friction. This means that the bottom-bracket of your cycle needs to be specially machined and prepared in order to accept a Schlumpf drive. At AlphaBENT, we've been installing Schlumpf drives since they were ever invented and we are experts at this process.

Other Schlumpf internally geared cranksets, Schlumpf installation

Other internally geared cranksets, Schlumpf installation brands