That jump between 4th and 5th is what would concern me. For the way I ride it would be ideal to have jumps from about 56 to 66 to 76 gear inches because that's where I spend most of my time. 76 g.i. gets me to a sustainable 20 mph on flatland and a good tuck position, my pointy head and substantial mass gets me above 30 mph downhill. I base this on the fact that I very rarely use anything outside of only three of the eighteen speeds available on my old 80's Nishiki Olympic training bike.

Even if I knew about that ti cog before ordering my Brompton and if it gave me the gearing I'm looking for (which it doesn't appear to be capable of), the $240 US price alone would have been a huge deterrent.

I think I'll just keep looking for a used crank and get the gearing I want for less than $100... because I'm stingy like that.