I replaced my rear Ultegra cog set from a 12/24 to a 12/27 on my Cannoondale R2000. Small cahnge but big results when climbing. I found a site where I can bump it up to a 12x30. I am just trying to justify in my mind the $99 to do so, so soon after. By the Spring, I will be making the change. Climbing is so much improved.