I had the 32 teeth chainring, since I do very steep and hard climbs, I decided to install the 30, the results were awesome. Now I can climb a lot easier and became more efficient regarding to speed on the climb. I simply have more cadences than before because I can switch or play with more sprockets you either go easier or faster on the climbs. My combination: 30 on front and 51 on the back (New Shimano XT group set, 12 speed)... Awesome group, it's really blowing the competition!!!;