Just out of curiosity, doesn't almost a kilogram weight of cage, bottle and water mounted on top of the stem rather spoil the bike's handling?
Yes and no. When you consider the change in overall CoG of the bike and hydration, it's a big relocation of weight. It's also locating the fluid (and its associated inertia) to a location with a greater degree of freedom. This is partly the reason why you don't see many handlebar mounted drink systems in the Pro Tour.
The question then becomes whether you'll notice it. I'd suggest that if you're weaving when using a regular bottle cage, then you may well not.
In an IM bike leg, however, there are a lot of differences we must consider - the goal is to time-trial as efficiently as possible, which means:
- Aero is king
- Wild movements and throwing the bike around aren't common
Both points have double significance: Firstly, a between the arms (BTA) bottle has been shown to be more aerodynamic than no bottle at all. (http://cervelo.com/en_us/news-blog/article/ask-the-engineers-hydration-and-aerodynamics/2930/) In addition to this, the penalty for coming out of the aero position to drink is reduced as one can drink more quickly.
As the most efficient way to ride is to keep as still as possible, the penalty of raised weight is negligible. This is even more so when we consider that BECAUSE we won't be throwing the bike around, we can consider the body on top to be part of the overall static weight - meaning that as a percentage, the delta for CoG is small.
So I'd stick with a BTA bottle for IM, but wouldn't use one for training or for bicycle races. The caveat here is the reason it was brought up in the first place - some people just find it easier!
Edited: 04/09/2012 at 13:09