I know this has been talked about in general and a recent post got me to thinking. I’ve been riding a P3 for the last 3 seasons and I always race (HIM/IM) with an PD aerodrink and two bottles in back of the seat. I “feel” like I’m going to mess up the “aeroness” of the downtube if I put a bottle there. My debate is if it’s on the DT it’s easier to get to, faster to remove/replace, less likely to bounce out, etc. I’m pretty fast at grabbing it from the rear but I get slightly more out of aero. I’m a strong biker and the better I get the more the seconds matter… So if you have a P3 what do you do? If you don’t have a P3 (is there anyone that doesn’t? haha) what are your thoughts? This doesn’t have to be “wind-tunnel tested” just opinions…
check out the bontrager aero bottle for the dt!
Its super aero and even dimpled! 
or this
So if you have a P3 what do you do?
I have heard that for both aerodynamics and for practicality the best set up for the P3 and similar bikes with only one water-bottle boss on the down tube is - one bottle on the down tube and then an aero-drink bottle between the aero-bar extentions. Dont bother with behind-the-seat.
My wife has raced many 1/2 and full IM’s with this set-up and never had a problem.
I just bought the specialized aero bottle to use for halfs. for sprint - olympic I only use a bottle between the aerobars, and usually remove the cage on the downtube. The other day I was wondering if my bike would be more aero w/ the specialized bottle on the downtube… Thinking I could still use the bottle on the aerobottles for hydration, and keep the specialized bottle empty, but on the bike for shorter races. Anyone have any idea if the P3 is more aero w/ this bottle set up? Thanks
Does that actually fit on the p3’s downtube?
yes, but there is some open space between the water bottle and the bike. So its not as clean as it may be on the specialized transition.
For the last 2 seasons, I’ve used a single “torpedo mount” for every distance, including up to 1/2 IMs. I’ll be going with the same setup in May for IMTX. I live off the course (at most I bring something solid to chew on stuffed in the back of my top). As close together as the aid stations are, you shouldn’t ever have a situation where your nutrition plan calls for something and you don’t have it available.
If you bring your own, then I got nothin’. : )
From my P3 a long time ago…
Do you think the time saved by not having more fluid is offset by having to slow down at aid stations.
In a IM particularly a hot one like TX I’d worry about having to slow down enough times to get a bottle, particularly in a crowd.
Styrrell
Also, back to the original question, is the bike MORE aero w/ the bottle? I like having two for longer races, keep water on downtube, and change out bottle on aerobars as needed . For a full, this may not be the bet water bottle to use as the cage is different, so you cant just throw a course bottle in the cage. You would need to dump into the specialized bottle which seems a bit much. For a full I think I may go w/ a traditional cage on downtube.
Any opinions on riding w/ it empty for shorter races, will that make me faster, slower, or really probably have no affect either way.
Wow, someone went searching old posts! haha. Since that post I changed my philosophy on my water/nutrition bottles… Up until '09 Clearwater I NEVER put a bottle on my downtube, I didn’t even put a cage on. Well at Clearwater about 5 miles into the bike my single nutrition (Infinit) bottle popped out of my back cage. I had a couple bars and gels for backup but I was bonking hard for the last 5 miles of the bike then trying to eat as much as possible on the run. Since that race I ALWAYS put my nutrition bottle on the downtube. If I were to do another IM I would put my second nutrition bottle on the back but I put one strip of electrical tape around it to keep it from bouncing out (BTW, did this at Clearwater but once you take the bottle out the first time, the tape is gone). So I really don’t care about aeroness anymore, as others have figured out it really comes down to the engine…I’m even planning to sell all my race wheels this year! Good luck all!