pengyou

Now that I know that I can load my Dahon up, there are a couple of mods that I would like to make. One is to put a 3 speed hub gear on it - I have seen some for about $100. The other thing I would like to consider doing is changing the chainring on it. As it stands, first gear is so low that I almost never use it. Is it possible to change the whole 7 speed cassette so that I have a more favorable gear ratio, given the addition of the hub gear? Which would be the least expensive? simplest? most durable? lightest? new chainring or new cassette??

fietsbob

SA 3 speed takes a 13t cog, high gear in the hub is 4/3 _ 1,33
so multiplying by inverse .. 3/4 = a 9.75 tooth equivalency.
so calculate the size of your chain ring based on that..

Alternatively you can get a special hub from Shimano, Capreo 32o R F-Hub
and a cassette unique to it ..9-26 9sp Shimano Capreo std cassette.
to get an even 9 tooth actual cog. + then you get the rest of the 9 speed stuff..

BruceMetras

I'm pretty sure a Dahon D7 has a derailleur and vertical dropouts.. so a 3 speed hub gear would be a bad choice (unless you're considering a SRAM Dual Drive setup, but those aren't $100) ... also, I recall the chainring being non-replaceable, as it is integral with the crank.. so, if that's the case and you wanted a larger chainring, you would need to replace the entire crank assembly .. I'd probably rethink what you want in gearing (usable gear inches) and how much dough you want to spend.