Originally Posted by
bthomas515
So I just swapped over from my old 9 speed Dura Ace group to a Sram and was wondering if to save a little cash if I could just convert my 9 speed cassette to a 10 speed? Its a 12-23 now and I found a 25 tooth cog online and was wondering if I could just add that to the end and go from there...
No, you can't. 10sp spacing is narrower than 9sp. And the inner cogs are offset on 10sp. You need to buy a 10sp cassette.