For most of my commute days I use my touring bike. It has been converted to an e-bike. So, I don't even think about weight - it's going to handle whatever I throw on there and it's not going to make a difference in my effort. So, for heavy days, it's e-bike. For lousy weather days it's e-bike (it has full length fenders and flaps.) Nice days, light load... I'd like to ride my carbon fiber road bike. I just looked at the carradice website. It stated that the mounting block should fit seat posts 25mm to 32mm - mine is 25.4mm.