Originally Posted by
pbass
If I did something like this I see myself sticking with whatever gear I started out in for the most part. For example, when I go out my front door, I have two choices--one way is straight up into the mountains, and the other direction is pretty flat. Right now my singlespeed is geared pretty low because of all the potential climbing. Could be cool to be able to swap my "singlespeed" gearing on the fly if I'm gonna head into town and stay in the flats all day. I can always just take my geared bike of course, but this idea seems nifty.
Once you get your main gear ratio figured out, in this case 2:1 via the 36-15 combo, you can then play around with the secondary gearing.
Combined 36-15 equals a total T count of 51T. Therefore 24-28 equals close to the same T count (52T) and should fit the same chain/dropout distance. I probably will wind up using 22-30 when I get another 22T chainring.
22-30 is a pretty low gear range and makes the dinglespeed worthwhile IMO, unlike other double cogs systems that only vary by a few T when probably I would be unlikely to bother to swap between a small variation and just crank through instead.
Ideally the change up gearing should be where it becomes too hard to crank in the preferred ratio so that the second combo extends the range of SS further.
The application doesn't really make sense for day to day urban riding but fills a niche for SSMTB or SS touring in regions with big long hills. The route from Hope to Manning Park for example, involves a 60km climb. You just can't ride that with a SS using a gear ratio that would otherwise be suited for more horizontal travel.