I'm gunning to get i shape and have some racing ..er.. 'fun' by doing some cx this season. I have cobbled togther a cx bike with an old ebay cx frame (alloy/carb forks), will either run cheap planet x everyman wheels or ksyrium equipes (from road trainer). I've slung my old ultegra gs on the bike but need a cx ratio chainset (esp as i aint got the strongest pins, more of a spinner).
I'm 5.11 and run 172.5 cranks on my roade bike (tho have rid 175). My cx options are 170 or 175. ANy thoughts on best option? Slight bigger or smaller than my road setup?
If you can, stick with the same crank length as your road bike (i know, not one of the options you gave?) - if you do most of your training in the winter on your road / winter bike standardised crank lengths is much better for your training and riding, will give a more consistent peddling rythm. If you had to chose one or the other, I would go for 175 personally.