Changed out the back gears from a 12/27 to a 13/30 so that I can survive the hills out here. We picked up the bike from the LBS and went out for a quick, but very hilly 10 miles. What a difference the gearing made! I've never been fast up the hills, but was always in agony - mashing, lactic acid... Today, I was spinning up a hill that last week tried to kill me