I just got a new bike with a 10-speed Ultegra 6700 12x25 cassette. I want to change it to an 11x25, which has the exact same gears as the 12x except that it has an 11 and does not have a 16. In other words, 11-12-13-14-15-17-19-21-23-25 versus 12-13-14-15-16-17-19-21-23-25.
My question is, does anyone know if the 16-tooth cog on the 12x25 can be removed and an 11-tooth cog added to the end? I ask this because I know the 21-23-25 is one piece. They cannot be broken up. And on my old bike, the 17-19 was also one piece.
Sorry, I don't have the proper tool to remove the cassette lockring (I know I should get one) and can't verify for sure. It certainly does look like all the cogs are separate except for the 21-23-25.