P3 water bottle placement

William Jenks

I'm going to race on my P3 with 2 bottles.  One will be a Speedfil A2 between the arms.  Question is where to put the other one.  I know this isn't the thing to make or break my race, but hey, a minute or two is a minute or two.

In these two photos, I have the two choices.  One is the traditional down tube bottle that everyone knows has a drag penalty.  The other is what's supposed to be a close-mounted single bottle in the rear.  From what I have read, the claims are that this is "drag free" and maybe even an improvement vs no bottle.  But as Cervelo says, things change with a real person on the bike.

The thing I question is that I have my saddle slammed way forward, making the gap between the bottle and the butt bigger than it is in all the beautiful pictures of how this rear mount practically scratches your back on the ride.  You can see the gap against the saddle, and in a not-very-flattering picture I asked OJ to take of me riding in the basement.  (I will not race with the second spare/equipment bag that is affixed to the bottom of the bottle holder in that photo.)

I have practiced with both and don't have any problem with accessibility of either bottle.

So what do you all think?  Am I still better off with the bottle in the rear or should I bail on the trendy solution and go with the down tube?

 

Swanie

I am also racing on a P3 and don't even have a down tube bottle holder. I used the torpedo bottle on the aero bars and a double bottle holder behind the seat. I tested this setup by tying yarn to the bottle necks and rode with bottles in both positions. The down tube bottle was catching a lot of air and the rear bottle hardly any. It was a no brainer for me. I have a mezzo bag under the rear bottle holder but it tucks up much tighter than the setup you have in the bottom photo. The whole setup is in my wind shadow.

zwuba

Behind the seat!! Cervelo did some test using their "dummy" rider and this is the best position and may even result in a slight aero-benefit!
Downtube is always negative ... pretty much the same applies to the seattube except you have a totally round seattube like an old-school road-race bike

William Jenks

Stefan - that was part of the reading I had referred to. I was concerned that the gap between me and the bottle was too much for that to be true, but I have no evidence one way or another.

Steve - understood about the bag. That's my "long training ride I don't care about aero" bag so I can carry a couple of tubes etc etc. I don't have hard data, but I am quite sure that my two-bottle setup that goes back there and that bag have an aero cost. I just "know" I go a bit faster at the same watts when it's off. Hence (also) my worry about this placement.

It's reassuring you both endorse the behind-the-seat single. I'll be curious to see if there is any counter-opinion.

Dawn Cass

I would lean towards the one on the back. I actually have the speed fill standard....looks like a triangle shape that mounts on the down tube. While they say that a bottle on the down tube is the least aerodynamic, I was told that the standard speed fill was more aero than having it on the bars.

That said, I have had this set up since the beginning of last season and haven't changed it. Perhaps I am out of date so interested what the peeps are saying.

Dawn

Peter Greagg

I have an old school P3, and like Dawn, I use the Speedfill on the down tube and a twin bottle behind the seat.

robin sarner

I think my set up is good. Very low bottles in the back though one is full of tools. Bottle between arms. Aero bottle to fill in triagle which todd k. Says is good. Two tubes go in aero bottle.

zwuba

http://www.cervelo.com/en/engineering/ask-the-engineers/hydration-and-aerodynamics.html

William Jenks

Thanks for the link.

Here's a money paragraph that answers my question: Narrow = good, but forward and back doesn't make that much difference.

You do want to keep the bottles (and whatever else you have stored with them) as narrow as possible to allow the air to come back together as fast as possible after it leaves your body. There was not a huge variation in drag depending on the position of the bottles behind the saddle, high or low, near or far. Many people use these systems for storage of tires, tubes, inflators etc. This looks to be a good location as long as they don’t stick out and grab air.