I recently bought a cheap Schwinn folding bike, as my Dahon was stolen last year . The Schwinn is single speed, and am planning to convert it to a multi-speed with an internally geared hub. The frame seems quite solid, but the one default gear is very short (maybe about 50 gear-inches or so?). 20" pre-built wheels with internally geared hubs don't seem to be common around here, and I'm not sure it would be worth the money to get something custom laced.
Here's a Sturmey Archer SRF3 in a 20" wheel, intended for trike use:
Looks like it might work, and the price is great. The included cog is a T20, might also try replacing it with something a little smaller like T17-T18.
Unfortunately, the trike hub is stated as being 130mm wide, and the Schwinn measures 110mm between the rear forks (opening to the back like a BMX-type). While the frame is steel, the forks on a folder are much shorter than on a full-sized bike, so I'm concerned that cold-set widening might not work well (any experiences?).
As an alternative, I see that Sturmey-Archer makes the SRF3 in some narrower widths too (but again, lacing the hub up would probably not be worth the price), and the 148mm axle has an overlocknut width of 108mm, perfect. I was thinking, perhaps it might be possible to get the Utah Trike Wheel, get a SRF3 hub in the narrow axle width, and swap axles?
I'm assuming the shell and other components across versions are the same. Not sure how difficult it would be to disassemble/reassemble, but the idea would be that afterwards, I would have both my wheel and a perfectly usable extra hub (now with 130mm axle) I could resell elsewhere.
I see some old info posted by rekall with a similar problem (regarding a BMX conversion). Maybe I'll be lucky, and I just need to take out some spacers to make it fit. The longer axle might interfere with folding a bit, but maybe I could Dremel the extra off or something.
Any ideas or comments would be appreciated, including sources for alternate 20" wheels. I'm in Southeastern Pennsylvania.