Planetary Gear Crankset
The Schlumpf Speed Drive acts like two chainrings on the front of your bike. In low gear, it uses a 1:1 ratio and gives you a gear of whichever chainring size you have installed. In high speed mode, it gears the chainring size up by 65 percent for a 1:1.65 gearing ratio.
For example, with a 30T chainring, the Schlumpf Speed-Drive makes it seem like a 50T chainring when in geared mode.
The Schlumpf Speed-Drive gives a sensible gear-range for most bikes and lets you eliminate the complication of the front derailleur.
With a 20" rear wheel using an 11-34T cassette and front chainring size of 42T, you can expect a gear range of approximately 23-118 gear inches, with a fair bit of overlap.
The standard Speed-Drive comes with a chainring. One or two side chainguards / trouser-guards can be added. The standard bolt drilling is 110bcd (pcd), but the Speed-Drive can be ordered with a 130 bcd bolt patter to fit the larger 130 pcd chainring sizes.
People looking for a large gear-range while eliminating the fuss of derailleurs can effectively use the Schlumpf Speed-Drive in conjunction with the Rohloff Speedhub.
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