Originally Posted by
Sammyboy
Ok. A 23 on an SA 8 gives me 30.4 to 92.8, and a 16 on a Nexus 4 gives me 43.7 to 80.5. For comparison, a road bike in 52 x 13 on 700 c's gets 105.1. It takes a lot of cadence to make up for 15 gear inches, and still more for 25! However, if I retain the existing cranks, or spring for cotterless where there are 60 tooth rings available, I'm better off. That would make the Nexus 4 50.5 to 92.9, and the SA8 35.1 to 107.1, which is a lot more like it. Hmmmm.
Four suggestions:
1. I frankly don't believe you need such high gears. The SA range you describe above would probably be enough most of the time; and though the Nexus-4 range doesn't have the top end, you'll really miss the bottom end. I'd try to get it down to 35 or so.
2. Compare the shifters and how well they'll fit different handlebar options. I had little trouble mounting the SA-8 perpendicular to the handlebar, but once that was done, I had a very hard time shifting it. It's a stiff shifter anyway, and I did not have it at a place where it was easy to shift.
3. Include, in your consideration of the shifter options, the Nexus Auto-D system, if you can find it. Some parts are available now:
http://cgi.ebay.com/Shimano-Nexus-4-...QQcmdZViewItem
Even if you can't find it now, you may find the whole auto-D system later (knowing your luck, I guess you will). You could mount the auto-D shifter anywhere, like somewhere you don't need to reach it, because it would do the shifting for you (just when you least expect it, no doubt).
4. consider what brakes will fit on those hubs. The Nexus-4 came in both a coaster and roller brake version. I have the latter. I have heard people complain about them, but I found it an excellent brake. I'm thinking on your Moulton mod, you will have a hard time mounting good brakes, so this is important. If you got a coaster brake and an Auto-D system, you could have a very clean looking bike.