Originally Posted by
12strings
You're probably right, I want to be able to keep up with my group riders that hold low 20's mph on flats for 30-40 minutes.
Most CX bikes have 46/36 chainrings up front. Going 80 RPM, you'll be going 22mph running 46 x 13. 46 x 11 gets you to 26mph. Higher than that will require higher cadence. You won't have any issue with the gearing keeping up with people going low 20s on a CX bike.