Where do I put my bike hydration? Part One: Look out behind you!

There are many systems now for fitting water bottles onto your bike. We'll take a look here at the broader categories, broken up by bottle location.

First up, and the subject for today's post, is the behind-the-seat option. Most rear bottle mounts will put either one or two standard water bottles at the level of your saddle or just below. The idea is that bottles positioned behind you aren't causing additional drag, because they're sitting in your wind shadow. A lot of people are using the rear bottle mounts for their switch-out bottles. They'll have one or two bottles in an easier-to-reach spot (like in the regular frame-mounted cages), and as they empty each of these bottles, they'll swap it for one of the bottles behind them.

Rear bottle mounts will typically attach in one of three ways. Most commonly, the mount will use brackets to attach to your saddle rails, where the rails slant up toward the back of your saddle. In the event that you use a carbon-railed saddle, you'll probably need some kind of adapter so the brackets don't damage the saddle rails. The brackets will fit pretty much any metal saddle rails.

A pretty standard saddle-rail-mount cage system.

Some mounts will attach to your seatpost. If you have a round seatpost, it's easier to find one of these that will work with your bike. Most tri bikes, and a good many road bikes, now use aero seatposts, so we don't see as many of these as we used to. It's worth noting that there are some seatpost-specific mounts, such as the X-Lab Sonic Wing, which fits only the classic Cervelo P2 and P3 carbon seatposts, and the Delta Sonic, which was designed to fit the new P2, P3 and P5 seatpost.

Delta Sonic - a single cage mount for the new P2/3/5

The X-Lab Sonic Wing mounts only to the classic P2/P3 seatpost

Direct saddle mount for the Cobb Gen2 - mounts one or two cages.

Lastly, there are some saddles that have optional integrated mounts. Cobb and Fizik have both come out with bottle mounts of this kind, Cobb on their Gen2 saddle and Fizik on their new Tritone saddle. These, naturally enough, are some of the easiest bottle mounts to install.



Advantages

Aerodynamics, as mentioned above, is one factor that leads people to use a rear bottle mount. The bottles sit in the turbulence caused by your body, so they add a negligible amount of turbulence themselves.

Just as valid a reason, however, is that bottles mounted behind you don't take up handlebar or frame space. You can use your aerobars to mount more bottle cages or computers, or you can keep the bars clean and clear. Pretty much the same goes for your frame cage mounts. You can use them for other bottle cages or keep them empty for aerodynamic reasons.

Disadvantages

The biggest disadvantage is probably that bottles are harder to reach when they're behind you. This is most troublesome if you only have rear mounted bottles. You'll be reaching behind you every time you drink, and that's not the easiest thing to do when you're in the aerobars (and it's not conducive to drinking much).

The other major disadvantage is the likelihood of ejecting a bottle, perhaps without knowing it until later. Since they're positioned behind the saddle, rear mounted bottles experience more vertical travel than you do each time you hit a bump or pothole in the road. If the cages aren't holding on tightly, the bottles (usually the ones with a pound and a half of water or sports drink inside) will fly out. To combat this, the wise rider uses a cage with lots of grip (X-Lab Gorilla Cages were designed expressly for this purpose), and angles the cages a bit backward, if possible. Angling the cages means that, in a bumpy situation, the bottles' upward velocity will throw them partly against the side of the cages instead of directly out the mouth of the cage.




Next week we'll look at frame cage options: the standard, the aero and the oversize!