Hi Robb,

In our testing, adding any bottle to a modern tri bike's frame, whether round or aero, has always added drag compared to no bottle.

Adding a plain round bottle between the arms reduces drag. See the data here: http://www.cervelo.com/...nd-aerodynamics.html



Cheers,

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Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)