Bump. This strikes me as a fundamental issue. Shouldn't 13-26 mean that the smallest cog has 13 teeth? The reason this is bothering me is because I actually counted all of the teeth on my 7-speed cassette, and came up with 13-15-17-19-21-23-25. I assume this means I currently have a 13-25 7-speed cassette on my bike, and based upon that premise I just put in an order for an 12-23 8-speed cassette.
So will my 12-23 indeed have 12 teeth on the smallest cog? Or what? What's going on here? Is this the twilight zone?