Thanks for the info.

Because I don't have the tech skills to do it, and the retailer from which I bought told me it was either expensive or right-down impossible to modify the World Sport to add more speeds. Considering the price of the World Touring Disc, I'll pass and buy a Dahon/Tern instead.

But out of curiosity, what parts are certified to be compatible with the World Sport, ie. it wouldn't take more than a couple of hours of work for someone qualified to make the change?

http://en.r-m.de/bike/world-birdy-sport/

I'd like a bit more speed than the current 56x11 when riding on flat roads, and more speeds when going uphill than the current 56x30.

The Shimano CS-HG40 is crap anyway: Even though the new cassette only has 500km's and I always start in 3rd gear (6 on the shifter) to go soft on it (and my knees), the first cog (11) is already "ripping" (don't know the right word: Feels like missing some teeth while cycling.)

Edit: BTW, is this the dual drive mentioned above?
http://www.bike-advisor.com/reviews/...e-27-2011.html