A Hydration System Teaches a Lesson


There's a lot of responsibility that comes with publishing aero data. Here at ERO, we've learned that we're in a unique position to provide the public with information that can have a significant effect on their purchasing decisions, so we take that responsibility very seriously. When you see published aero tests, you as a consumer need to know whether or not the conclusions from those tests are accurate. Too often, we see tests which are conducted poorly; sometimes it's a lack of experience, or perhaps poor methodology which leads to inaccurate outcomes, sometimes it's a desire to find a specific result. However, there's one mistake we see over and over again that almost guarantees an aero test will be bad...lack of thoroughness.


Here's the deal. Getting good results from aero testing takes effort. It takes testing the same thing over and over again to insure the results are consistent and, perferrably, it takes testing multiple set up options to determine how a position change or product works best. What it really takes is something we all tend to lack: time, and something many of us need: patience. Before we really get into publishing aero data for you all to see and digest, we wanted to show you how a small change can make a large difference, and how if you fail to take the time to look, you might miss something very important.

Right now, we're trying to put together some numbers for testing front hydration systems; something that would seem pretty straightforward on the surface, but like all things aero can be quite complex. One of the systems that has really stood out is the Profile Design FC35. It's quite good aerodynamically, but we might not have known it had we failed to investigate it thoroughly. As it turns out, like many products, setting it up properly is the key to it's success. Proper set up, though, isn't always obvious, or even what the manufacturer instructs you to do. Let's take a look...

If you look at Profile Design's web site, or search for photos online for the FC35, you'll see the hydration system set up like the picture below. Very standard...easy to do. Strap the mount to the aero bar extensions. Slide the bottle in place. Boom, you're done. Idiot proof, yes? Well, yes, actually, it is, and it works quite well. Most everyone we speak to really likes the FC35 - there are some complaints about the little storage box in back not holding items down particularly well, but nothing a thicker rubbber band doesn't take care of, that's for sure. All-in-all, it's a great product that serves athletes as intended. So, by all means, mount it as intended...and you'll go slower with it on your bike! Wait, what? Slower? Why slower?

How you're instructed to mount the FC35

If you attach the mount for the FC35 right-side-up, as intended, it will very likely slow you down. BUT!!! And, this is a big but (no, not that kind fo butt, stop that), if you mount it correctly, the FC35 is just as likely to be one of the fastest front hydration systems out there. How? Well it's a simple change that makes a world of difference.

The FC35 is a pretty big bottle. If you install the mount upright, the bottle ends up sticking up pretty high in the air and increases your frontal area. Not good, and your drag increases accordingly. Don't fret, though, the solution is quick and easy - turn the mount upside down. Yep, that's it, just turn that sucker upside down so it hangs below the extensions instead of above. By doing so, the bottle suddenly drops in between the extensions and, voila, you just went from increasing to decreasing your drag! Quite a bit for a BTA system as it turns out.


How you should actually mount the FC35

Here are the numbers (yes, the CdA's are high - big test rider in a very good aero position, but big nonetheless):

Test  CdA  Watts - saved or lost(-)
 Baseline Test  .2982  
 Profile Design FC35 - Standard Mounting Position  .3003 -1.7 
 Profile Design FC35 - Mount Upside Down .2881 8.3

What does the above mean? Well, if you install the FC35 in the standard position, you're going to lose approx 1.7 watts in aero drag. Not a huge deal, but measureable. However, if you install the bottle lower, with the mount turned upside down, you gain a whopping 8.3 watts from Baseline; 10 watts from the standard mounting position! That's pertty significant, and we repeated the results 3 times. Nice. So, your first conclusion is obvious - the FC35 is a very good BTA aerodynamically. Set it up correctly, and you'll lower your drag. But, there's a bigger takeaway here that's really the whole reason for this article.

The main point is this: testing a particular product isn't as straightforward as it would seem, and you should always question the results.  My guess is most testing would have stopped with the standard installation of the FC35. Imagine a test for a magazine or e-zine; the initial results would have been published as the final word on the product, and you, the consumer, might have decided against the FC35 based on the results.  We've seen this before: bad testing protocols, lack of thorough testing, or a failure to investigate other means of use. That might give you something to read in an article, but it doesn't help you; it doesn't educate. Isn't that what aero testing is supposed to do? Isn't it suppose to provide you useful information to make sound choices for better performance? We think so, so we want you to questions any results you see, whether they're from the sports media, a manufactuer, or ERO Insight. We want to be thorough, and we're learning all the time. Question our results. Provide critiques. Make suggestions. Demand that we, and everyone that publishes aero data, are providing you with the best data possible. Let's learn from one another.