My examination of drive ratios of the SRAM S7 hub has led to examination of other hub gears. I now have information on a very large number of hubs posted online in a Web version of a Microsoft Excel workbook — which includes a link to the source Excel file too.
The workbook gives exact (fractional) gear ratios as well as decimal approximations, and corrects a number of minor errors in manufacturers’ literature and online gear calculators. For most hubs, the information is calculated directly from gear-tooth counts and an examination of the hubs’ internals. The workbook page about each hub therefore indicates how the hub generates its ratios.
Thanks to the excellent Sturmey-Archer Heritage Web site and to documentation on the site of Tony Hadland, author of the book The Sturmey-Archer Story, I have information on Sturmey-Archer hubs all the way back to the first model sold, in 1902. I also cover most geared hubs from SRAM (and the companies it absorbed) and Shimano, and the Rohloff hub. Please see the acknowledgments page of the workbook for a list of people who have been helpful. Coverage of additional hubs will be added as the information comes to light. If you have information to contribute, please don’t be shy!
Why am I doing this? I’ll admit, I’m a bit of a math nerd. It’s been bothering me for years to see only inexact, and sometimes incorrect, decimal numbers given for the drive ratios. But also, I am writing an article for the technical journal Human Power about trends in the design of internal hub gears. My research toward the article has generated the information on drive ratios.
