i don't know the answer, but I'm curious why you can't get away with 2 bottles. How far apart are the aid stations? How many bottles total do you plan on going through? but i'm not trying to talk you out of 3 bottles

Would it be two water bottles then calories in the aero bottle? Or will you have calories in all then just exchange?

If you’re using water in bta and bts athen aero bottle would be best/most aero option.

But if you need calories in all 3 then I’d go double bts and single bta to keep the frame clean.

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Fair enough. When I say "dead set", maybe I'm not actually so dead set, but I will make a decision as the event gets closer and I have a chance to practice hydration/calories more. Its been 10 years since I've done a 70.3. Depending on conditions, etc., I anticipate taking in about 100 fluid ounces and 750-1000 calories and I do all liquid calories (Infinit) so I plan to distribute those over two bottles and then fill the third bottle up with water and swap it out at aid stations. Depending on what I believe my caloric need to be, I may be willing to condense those down to 1 bottle, but I don't want to make that bottle too concentrated.

Nothing inside the triangle. Go with 1 BTA and 2 BTS. That is max aero. Cervelo did a aero study on bottle placements, but I cannot find their original pdf.

Yes, they did but that was with round bottles On the downtube. Aero bottles are obviously better, and I know double bottles BTS are slower than single BTS so when you shake all that out...???

How much drag there is for BTS depends on how much of a gap there is between you and the bottle cages. If you sit on the front of your saddle and there is a gap between you and the bottles it is slower than if the BTS bottles are directly behind you. I believe even the Cervelo article also mentions this. I don't know how big that gap can be before BTS starts being slower than no BTS.

Personally I race with 1 bottle between my arms, and 1-2 bottles BTS depending on distance with nothing on the frame. I'm a MOP racer so the few seconds it may cost me wont make much difference in my overall race results.

first question, what kind of bike do you have? What aerobars? What extensions? Let's do this right.

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have you considered a Torhans Aero 30 or Profile FC35 slung low? I'm assuming you have a TriRig front brake. There are aero positive solutions (to include the Profile Design Aeria hydration system slung from their new stem) to consider rather than just a merely aero neutral BTA bottle.

Also, there are some really tight 2-bottle BTS solutions... google Sebastian Kienle for one.

Eric

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Eric Reid AeroFit | Instagram Portfolio
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Thanks...

I have Magura brakes.

I am considering new that PD set up, but my current set up basically requires me to use Tririg N35 to get more stack which limits me somewhat, including using the new PD stem/bottle. I may change that eventually if I can train myself to get lower. In the meantime...

I have used the PD FC35 (with bracket turned upside down) before but (1) it was still fairly off my headtube so not sure how much aero benefits I was gaining, if any; and (2) I don't care what the claims are or what others have experienced, that thing splashes a lot. I would/am possibly considering trying it again and only using water so splashing is less concerning, but I swear to myself I would stick to simple cage BTA after using that (and many other brands). Of course, if the bottles handed out on course don't fit tightly in the BTA cage, that plan isn't great either. I see same potential issues with TH--I can't get it anywhere near the stem and my understanding is aero benefits are not there if you cannot do so.

I will google Kienle.

Why not use xlab torpedo? Zero spillage with the solid cap and easy to refill. Also we need a pic of you on the bike side profile.

Here's what I do....

Single round bottle BTA and single round BTS. Both with calories in them. In my 70.3s I have done 3 servings of GU Roctane, which equates to ~750 calories. When I finish my first bottle (BTA), I put it in the back. When I get to the first aid station I chuck the empty bottle and grab one with water in it and throw it BTS to have with me. Take a bottle at every aid station, take a drink and spray it on you if needed, then chuck it, that'll get you probably 4 big drinks over the 56 miles which has always been enough for me plus my 2 bottles.

Never more than 2 bottles on the bike at a time, and both hidden very well from the wind.

I’m familiar with—and have tried many of—the various “fancy” BTA options. Some more than once. They didn’t work well for me before but I was also doing shorter distance. I’m open to trying again but I have a feeling ditched them for a reason and won’t like them anymore the second (or third) time.

Interesting thought...I need much more fluid than that and I find aid stations to be disasters—wet, bottles potentially everywhere, awkward biking by riders etc so I would prefer to minimize the number of times I need to use them.

Ran 3 cages for my first 70.3. Will only run 2 in the future. Plan was originally only bta with water (profile design aero hc) and bts 6 scoops of infinit go far (~850 calories). I don't mind it that concentrated, just a few sips of water after.

Weather was in the 30s, so I put a cage in the triangle and stuck my calories there instead of BTS and went with extra water in the BTS. I was afraid cold hands would make refilling the bta and getting my calories from the BTS difficult. But looking back, would have been no issue to stick with original plan. Tossed my BTS bottle at the second aid station after using it to fill my BTA. Tried to stick an on course bottle in the rear cage and couldn't get it in (gorilla cage was too tight for the soft plastic). So next aid station forced me to catch a bottle, refill, and toss before the last trash. Not an issue at all. No spilling, didn't feel unsafe at all. Eyes on the road and hand on brake at all times as I had the cap popped and ready to go before reaching the area.

Will revert back to the 2 bottle system for future 1/2s and fulls with more nutrition in special needs for a full.

XLAB (and others) have done some wind tunnel tests that might interest you:

https://www.xlab-usa.com/aerodynamics.html

I am riding with one bottle between my arms using the Torpedo Kompact and swap it at every aid station. I am aware of the benefits of an aero bottle but I think it is easer to just swap bottles instead of refilling it. I am a light rider so getting rid of the extra weight of two bottles behind my saddle helped.

Refillable BTA or a standard bottle so you can switch around?
All bottles interchangable? (i.e. all with similar contents)

If the're all being used for the same liquids and the BTA is not refillable, a frame bottle isn't great. You'll be getting out of position to reach for it. It's less of an issue if you were just putting some gel or concentrated carbs in it that would only be used occasionally. And could be a decent solution if you will just use it briefly to fill the BTA.

A refillable BTA is more foolproof. You can use either 2 BTS or 1 BTS and an aero downtube bottle and just move the liquid to the BTA when needed, thus staying in position almost the entire time. Choose whether 1 or 2 BTS depending on aerodynamics and capacity. If you can get 2 bottles close behind you, that's probably fastest and most versatile.

Next best option is a standard bottle BTA (i.e. replacable, not refillable).
If going this route, you'll be wanting 2BTS and no down tube bottle since an aero bottle can't be moved to the BTA location.

[Edit] Another advantage of 2 BTS is that if you decide 2 bottles with one being BTA is enough, you can just remove one of the BTS ones, which are cheaper (unless you buy crazy expensive and unnecessary Gorrila cages!). You won't want the aero bottle if it's BTA+1. You'll want a standard cage for swapping bottles at aid stations. A shame to buy an aero bottle and then shelve it!