I've been riding this season with 3 bottles - water in a Torpedo, calories on the seat tube, and a spare behind the seat to stash water as needed. I just read about someone going to the wind tunnel and dropping ~7 watts by ditching the seat tube bottle and holder. I also saw recently that two bottles behind the seat comes at zero cost.
So my question is obvious - any down side to dropping the seat tube and going with two behind the seat?
So my question is obvious - any down side to dropping the seat tube and going with two behind the seat?