I'm about to pull the trigger on a B'Twin Cyclo X, but need some advice on ratios. I do plan to enter some cyclocross races (for fun), but this bike will also be used for local XC rides as a replacement for my MTB. The going is seldom very rough (no big drops), but there are a few very steep (20%+) muddy climbs on my regular loops. I have tackled them on my heavy tourer in dry weather, but that has a mid range triple.
The Cyclo X comes with 46-36 on the front and 11-28 on the back. I know this is already quite a wide range for Cyclo, but I do want to stay in the saddle for the hills. The groupset is 10-speed Shimano 105, with what looks like a standard short cage derailleur, for which Shimano recommend a maximum of 28 at the rear on a standard compact. In view of the narrower-than-compact front range (46-36) is it possible to run a 30, or even a 32 at the back? Even with that range I'll still be pulling a longer gear than I'm used to, but carrying around 6kg less bike (and improving fitness, I hope!). I'm 40 years old, 6'5" and unlikely to see much below 14st ever again, to further explain the need for a bigger cog.