I would like a 14-27 ultegra 10 speed casette. Shimano does not offer one. I am thinking I will purchase the 14-25 and interchange the 21-23-25 sprocket unit with a 21-24-27 sprocket unit for a 12-27. Will this work?
I am concerned for I notice Shimano has 3 different part numbers for a 21-23-25 sprocket unit dependant on the rest of the casette. In this case 12-25, 13-25, 14-25. Why aren't these interchangeable? Or are they?