Originally Posted by
poetman
Is there a way for me to figure out the gear ratio difference between the current 18 to a 21 or 22? After I took it for a ride, I felt like first gear was awkward: it didn't help me climb a hill, but I also would not want it to be my level terrain gear. Maybe my current second should be my new third gear? I'm trying to figure out how the gear numbers compare between the current 18 and a 21 or 22. Where does first gear on a 18 fit on a 21 or 22?
Old English The common Sturmey-Archer three-speed hubs provide a direct drive middle gear, a high gear that is 4/3 of the middle gear, and a low gear that is 3/4 of the middle gear. (The principle of operation is explained on another page on this site.) Among current hubs as of 2010, the S3X fixed-gear hub is different, with two step-down gears and a direct-drive gear, and a special Brompton hub has a wider range to use with two sprockets and a derailer for a total of 6 speeds.
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By modern standards, the typical English 3-speed bicycle is geared rather high. Most have 46/18 gearing, which gives gain ratios of 3.83, 5.11 and 6.81 (50, 66, and 89 inches; 4.00, 5.28 and 7.12 meters.) You can make riding a lot easier by customizing the gearing. 20 and 22 tooth sprockets are readily available, as well as smaller sizes for speed demons or small-wheel bicycles. It is also possible to modify Shimano cassette sprockets with a Dremel grinder if you need something bigger. This is not particularly difficult to do. There is more detailed information on this on another page.
Sturmey-Archer has manufactured many models of 3-speed hubs over the years.
Servicing Sturmey-Archer 3-Speed Hubs
...you should go to the page linked, as there are other links in case you have other questions.
Also,
here's the official gear calculator, which has the stuff you need for a number of IGH hubs to figure your gear ratios using different chainwheels and cogs. But it only helps if you know from prior experience what are good lows and highs for your particular tastes. I use it to set most of my derailleur equipped bikes to a range of about 3 to 8 or thereabouts, but I will arrange things differently if I'm planning on carrying a load, climbing a lot of hills, or trying to simply get a good selection in a close ratio setup for racing.......which I don't do any more and was never very good at.
