The ingenious Schulmpf cranksets utilize a heel-activated, two speed planetary gearing system in the bottom bracket and spider to achieve a high and low range without multiple chainrings, front derailleur, or shifter. Schlumpf cranksets are available as a Mountain Drive, Speed Drive, or High Speed Drive. The Mountain Drive uses a direct drive 1:1 ratio, and a low gear 2.5:1 ratio. The Speed Drive uses a direct drive 1:1 ratio, and an overdrive 1:1.65 ratio. The High Speed Drive has an integrated 27T ring with a 1:1 ratio and a 1:2.5 overdrive. All fit standard 68mm bottom bracket shells and all are also suitable for tandems. The efficiency of the planetary gears is 95 - 97%.
Prior to installation, your bike's bottom bracket must be chamfered at 45° on both sides. Chamfering will not affect normal bottom bracket installation in the future. Trike booms can be shipped to the Hostel Shoppe for chamfering (nominal fee of $60 plus return shipping). Please call the Hostel Shoppe for chamfering options at (800-233-4340).
The Mountain Drive comes complete with bottom bracket, spider (130mm BCD), crankarms (black 170mm), crankarm bolts, shift buttons, and tube of lubricant. Chainrings not included. Also includes a steel cone for aluminum bottom bracket shells, and an aluminum cone for steel bottom bracket shells.
For information on measuring your chainring bolt circle diameter (BCD), click on the link to our help page Here. For Schlumpf Drive installation documents and manuals click on the Schlumpf Drive resource page Here. More information can also be found on the Schlump Drive FAQ page Here.