Look inside . . .
It's probably a 1 1/8" (1.125"), or 28.6mm, but unfortunately there's no solid correlation between seat tube and seat post. I just replaced my road bike frame, and even though both had 27.2 seatposts, the old bike took a a 1.125" derailleur and the new bike takes a 1.25"
But the way to be 100% sure is to take off the old one and look inside the band. The size is stamped right there, just like your seatspot size is on the end of your seatpost.
It's probably a 1 1/8" (1.125"), or 28.6mm, but unfortunately there's no solid correlation between seat tube and seat post. I just replaced my road bike frame, and even though both had 27.2 seatposts, the old bike took a a 1.125" derailleur and the new bike takes a 1.25"
But the way to be 100% sure is to take off the old one and look inside the band. The size is stamped right there, just like your seatspot size is on the end of your seatpost.
