We've had a thread on gear ratio for city riding but what about fast hilly group rides? I currently have 42x17 which is perfect for city riding and pretty comfortable on hilly rides at a 21mph average pace. On Saturday I rode with a group that averaged about 25mph and I was spinning like a madman the whole ride (but didn't get dropped). I'm thinking about dropping to a 42x15 but am worried that some of the hills will destroy me.

What gearing do you use when you ride with roadies?

So if you found yourself undergeared on the flats and overgeared on the hills that means your gearing was perfect right? :)

Yeah, I get dropped on every long hill and need to kill myself to catch up with the group. catching up with a fast group multiple times in a 50 mile ride is the sort of mental training you don't get in many other sports.