BTW, if you are talking about CX racing, as opposed to just riding off road with your CX bike, I don't know if 12-30 is the way to go. In my experience, the chain seems to find its way onto the lowest gear I have and if I don't limit how low that is while I'm not in the pain cave I find myself dropping off the back in a hurry. There are a very few cases where I like to have a super low gear but in general it tends to work against me.