I am just curious, being rather new to tri’s and all, why so many triathlete’s place two bottles behind their seats, and not on the frame? It just confuses me? Any Ideas? Because aerodynamically, placing them on the frame is superior, especially in windy conditions.
This has confused me as well! Especially, when you see a triathlete with bottle braze ons on their down/seat tube- but no bottle cages there! In my case I only have one bottle mount- on a P3C… so… in order to mount another bottle- I use rear hyrdro tail with one extra bottle centered.
As to the reference that you posted- my brother has a P3C- and it is more aero NOT to carry a drink bottle at all for that particular model (good to know for a pure TT or sprint race)- per his wind tunnel testing- so when Cobb says- carry a drink bottle- it might be for more round tube bikes… versus some of the aero tubed tri/tt bikes.
Not necessarily. Did John Cobb test with or without a rider?
We’ve done the same test before… yes, having a bottle or two behind your seat does slow the bike down when you’re not sitting on it, but when you’re on the bike, the bottles are covered by your wake. The bottles don’t even see the wind.
And putting a bottle on your seat/down tube does different things with different bikes. It’s better for some bikes (especially those with non-aero seattubes), but is a general no-no for aero bikes.
The only bottles that we’ve tested to actually improve your aerodynamics is the MIT top-tube bottle (look out for it soon!), and the profile design aerodrink when mounted near enough to the headtube.
His test was with a rider, and I think was primarily dealing with crosswinds, not headwinds.