Where do I put my bike hydration? Part 2: On the hypotenuse.

In part one of this post, we covered rear hydration mounts. Moving forward, we find the most traditional place to store bike hydration: on the downtube and seat tube of your bike frame.

Most road bikes today have water bottle cage mounts on both the downtube and seat tube. Most of us are pretty familiar with those mounts and with the usual aluminum, nylon and carbon cage options that fit them. Triathlon bikes, by contrast, don't always have both sets of bosses. On the old and new carbon tri frames from Cervelo, for instance, the cage mount appears just on the downtube. The Felt DA frames only have mounts on the seat tube. In these cases, only one cage can be conventionally mounted in the front triangle.

The classic P2 frame. Bottle cage bosses appear only on the downtube, at left.

If you're mounting standard bottle cages (or one standard cage) on the downtube/seat tube, you can play the swap game - moving full bottles forward from a rear cage mount, moving empties back. This kind of setup is great if you have to ride long distances carrying your own nutrition (like if the drinks provided on a given race course don't agree with you). Mounting a pair of standard bottles in the front triangle also, by the way, can be the cheapest way to carry hydration on the bike. Cheap cages are cheap, and so are cheap water bottles.

Some triangle-mounted hydration systems incorporate a flexible drinking straw, which can be run up to your aerobars. Speedfil is probably the best-known system of this type. The straw in these cases is largely a matter of convenience, though I've also found that I remember to drink more often when I have a straw right by my mouth. For the aero-minded, the straw also means you don't have to sit up or take a hand off your aerobars to drink.

Felt DA tri bikes come with the TorHans VR aero frame bottle.

As a third option, there is the aero frame bottle. It's not just a bottle for an aerodynamic frame; it's an aerodynamic bottle for an aerodynamic frame. The Profile Design RZ2, X-Lab Aero TT, TorHans VR and Arundel Chrono are all versions of the aero frame bottle. X-Lab claims a 50% reduction in drag if you use their Aero TT instead of a round bottle.

One downside of using an aero frame bottle is that you can only fit one of them on your frame. Even if you have two sets of cage mounts, the aero cage takes up too much space to mount a second bottle. The other significant downside is that you can't switch bottles out during a ride or race. The aero cages will only fit their respective bottles...unless maybe you shove really hard. Some of those race support bottles are pretty flimsy.


Last thoughts on the downtube/seat tube mounts:


I think the only disadvantage to mounting your hydration inside the front triangle - using bottles or systems of whatever form - is the potential increase in aerodynamic drag. Most riders will be familiar with reaching for bottles below them, and the cages aren't really taking up space for anything else. Additionally, as mentioned above, this can be the least expensive way to carry hydration on the bike.