The recent development in geared bottom bracket/crankset has been an encouraging sight to many folder fans, because it is a technology that would benefit us much more than other cyclists. The market's grown from one single supplier to four: Schlumpf (Speed-Drive), ATS (Schlumpf licensee), Nicolai (B-Boxx), and the big fish SRAM (HammerSchmidt). However, it is slightly disappointing that all these products are of two speed.
A couple years ago someone posted a video of a 5-speed Strida mod based on the Shimano FM-5 geared BB. Wondering why we haven't heard more about it since, I dug around a little bit and found the following:
- FM-5 were in the market for a very short time, therefore old bikes with FM-5 are extremely difficult to find. Lots of enthusiasts want to get their hands on one but can't.
- This guy managed to locate one but it was in a bad shape. He cleaned it up and found that the crankset weighted 3.6 kg! The gear ratios are 1.00, 1.31, 1.59, 1.91, and 2.21.
- What really surprised me is the existence of another Japanese multi-speed geared BB—"F4" made by Bridgestone. This 4-speed system was in the market longer than FM-5 and seems somewhat easier to find today as a result.
- You must see this amazing mod! Aforementioned F4 mated to the tiny HandyBike! (Skip to the last link if you have no patience for all.)
So it can be done. Let's hope that the market's renewed interest in geared BB can convince Shimano and Bridgestone to revive and modernize these ingenious systems, or at least license them to someone else.