The Between-The-Arms (BTA) bottle is the first and most important place to figure out a good hydration solution for your setup. BTA is the most aerodynamic way to mount any bottle according to several industry experts. Take a look at the picture adjacent - there's a bottle in there, even though you can't see it. It's totally hidden from the wind. Mark Cote, chief aerodynamicist at Specialized for many years, has even said it tests faster than not having a bottle in there at all! This is true because the BTA bottle, if properly positioned, fills up the gap between your arms, so that the wind can flow around them better.
Just a few years ago, the options for drinking from the aerobars were very limited. You either zip-tied your own cage onto the bars, or used the Profile Design Aerodrink. And that was basically it. Funny enough, that zip-tie solution continues to be a very cheap and effective way to add aerodynamically neutral (or better!) fluids to your rig. But, with the march of time, a lot of very good products have entered the market. We are not going to go over them all in this article, just our favorites in a few categories. There are links at the bottom of this page if you want to explore more choices in depth.
Complete retail system - Profile Design HC Bottle
(Read our full review of the Profile Design HC Bottle). The Profile Design HC Bottle is probably my favorite retail product, because it's basically what I would have designed if I were trying to make a custom BTA bottle. It's built just for BTA applications ("HC" stands for "Horizontal Cage"), and it does a really bang-up job at its function. First off, it's built a little bit like a regular bottle; it has a removable top that makes it very easy to clean, and that top has a bullet-like shape that serves as a decent leading edge. Of course, that might be moot, because if your hands come together, the wind will never see that leading edge anyway. But nevertheless, that top covers a bottle that's basically perfect in terms of design. The tab indentation (where the top of your cage captures the neck of your bottle) only exists on the bottom, serving to keep the bottle centered, with the straw pointing up. The refill cap is nicely above the top of the bottle's water level, avoiding the splashing situation from which other bottles suffer. That refill cap is faired, as not to present a circular cross-section to the wind. The straw mass is similarly faired, for the same reason. Beyond that, it's very simple, straightforward, and works very well. It has become my favorite retail BTA system, and there's very, very little to complain about.
Next we have my little DIY number. The "Homebrew" isn't an actual product, it's just a little toy I made using a standard water bottle and a length of plastic tubing from the local hardware store. This is without a doubt the cheapest option, costing maybe $2 for the bottle and $0.50 for the straw. And it works like a charm. I've seen other people do this kind of thing in the past; it's not my invention. But for mine, I took the extra steps of sealing the straw junction with hot glue, and then poking a pin hole on another spot for an air return. This keeps water from splashing out on bumps, yet it is still easy to drink out of. I also put a Camelbak "Big Bite" valve on the end of the straw (not shown in this picture), which keeps the water right at the tip of the straw - no need to suck air on each sip. In fact, I usually put one of these bite valves on every straw that I use.
Using a regular bottle in a BTA cage is still a very good option. There are now a lot of options for complete systems, but many people (myself included) still prefer the convenience of a standard cage and a standard bottle. You can use whatever bottle you want (Course bottles fit nicely), and you can transfer bottles from other parts of the bike on a long training ride for more convenient access. If you are still unsure of what you want, this is probably the best way to go. Give it a try, and then decide if you want or need something more complex with a straw or quick fill port.
More reading on BTA Bottles:
- BTA Hydration Shootout
- Review: Profile Design HC Bottle
- Review: TorHans Aero 20
- Review: TorHans AeroZ BTA Bottle
- Review: Speedfil A2