Best place to mount water bottle?

[big booty]

I watched an episode of BCN on youtube and they said that it was better to mount your water bottle cage on the seat tube rather than the down tube with respect to aero efficiency. Not sure why it would make a difference? Has anyone looked into this or better still does anyone have data (power meter??) to show this is true?

[Alex Simmons/RST]

It's variable. The differences are small, and require sophisticated analysis methods to test. Perhaps a link to the video so we can at least see what they did?

[softy]

I would say it all depends on the design of the bike,

My Cervelo S5 says it should be in the lower position on the front down tube. TT bikes like to run them dehind the seat.

I don't believe it is a one solution fits all.

[bychosis]

Overall it's probably more efficient to mount it where you can reach it the easiest for a drink. I've had a bike where they were mounted :
behind the seat: difficult to reach to return them, bottle rockets over bumps.
Under the down tube: keep getting tyre buzz on your fingers while retrieving the bottle on the move, not to mention the extra reach.
More difficult to reach/return means more time off the power stuffing around with your bottle.

[kenwstr]

I have one on each tube, the down tube is easiest to retrieve and replace. Interested to know if its based on theory or actual wind tunnel tests.

Ken

[Duck!]

For efficiency of use, down tube is considerably easier, however in aerodynamic terms seat tube is a bit better, largely because the airflow is already getting turbulent from the rider's legs, so the bottle isn't having as much effect causing turbulence. Same deal with saddle-mount bottles on a TT rig; they're in an already turbulent zone behind the rider, so they don't contribute much more drag.

[KGB]

^ makes sense. I was wondering if it was something to do with the bottle disrupting the smooth, laminar flow of air before the wheel. I vaguely remember from uni something about in certain cases it is faster to pass through already turbulent flow rather than disrupt a smith flow of air. I think that was the principle behind speed skaters having the zig zag stitching on the forehead of their suits.
In any case, aerodynamics is not a black and white area, each case needs to be tested individually. Aero helmets are a perfect example, what may be the fastest helmet for one person is not necessarily the fastest for another.

[big booty]

Finally found the clip again. Its the #3 tip towards the end.

https://www.youtube.com/watch?v=Zf3q9ASKLts" onclick="window.open(this.href);return false;

[softy]

I know for a fact the Cervelo S5 has been designed specifically to have the bottle on the two lower cage bolts on the down tube for maximum aero.

As I said before, bikes are not equal.

[g-boaf]

I would say it all depends on the design of the bike,

My Cervelo S5 says it should be in the lower position on the front down tube. TT bikes like to run them dehind the seat.

I don't believe it is a one solution fits all.

Hmm...





First one mine, last one a sister bike (R. Hesjedal). Behind the seat tends to be only triathlon bikes using the X-Labs or other bottle cages that connect to the saddle rails. I have them as well, but only use them if I'm doing a very long ride on the TT bike where I need to carry an extra bottle and one for various others odds and ends.

The article below has more on the second bike (from Garmin Sharp):
http://www.cyclingweekly.co.uk/product- ... ike-131621" onclick="window.open(this.href);return false;

The mods to the Arundel Chrono bottle holder are telling, mine has the same problem - over bumps the bottle is prone to flying out of the cage. So yeah, cool looking bottle and holder, probably aero but needs some mods to make it work better. A normal bottle holder is probably easier, even if not so aero. I've seen them using an aero Camelbak bottle as well. XLabs does one too, but no idea how well it works.

On the down tube is more practical for most bikes, easier to reach. I don't know about aero effect of that, but on most road bikes, the effect would surely be minimal? On a TT bike like mine, it's downtube only, that's the only place to mount the bottle cage, unless you want to fit it between the aerobars, triathlon style or use saddle rail mounted bottle cages.