Let me test everyone's attention span...
Position is obviously where an athlete can find the most significant gains, but it's also important because it effects virtually everything else.
To worry about any other item on the list (wheels/tires would be the exception) is, for the most part, a waste of time until your position is dialed biomechanically and aerodynamically. And, let me tell you, you can really go deep here; the complexities can drive you mad, and I'm sure my wife could present an argument that they've already taken me down the road to being a window-licker on the short bus (I know that's so very wrong - I'm sure I've insulted someone). Let me give you an example (of the complexities, not my mental state):
- Your position will effect how a helmet may, or may not, work for you.
- Your position will effect how clothing fits you.
- Your position will effect the front end of the bike; not only with the setup to attain your position, but also how your body interacts with the airflow around the equipment.
Let's get back to shoes covers (booties). We're going to have to assume a few things with this scenario, so just roll with me on this for the sake of making my point, and don't get too picky.
Let's say an athlete tests a set of shoe covers and sees a decrease in CdA. For the next run, I decide I want to lower the athlete's seat position by 1cm because i believe there's too much knee extension at dead bottom center. Let's assume I'm able to keep all else equal by adjusting for drop, reach, etc. - heck, I'll even say we changed crank length to normalize for flexion of the knee at the top of the pedal stroke. In fact, we'll suspend belief for a moment and state that the only change resulting from the saddle height adjustment was the knee angle AND the angle of the foot at dead bottom center, which measured a drop in the heel of about 3 degrees (not uncommon). We conduct our next run and see that CdA has risen. Disappoinment. Why would it get worse of all else was equal? Well, I could make an argument that the increased drag was a result of the change in foot angle and, therefore, a change in how the shoe covers fit. Could a simple change in foot angle result in an increase (or decrease) in CdA? Certainly, we see the smallest of seemingly innocuous adjustments have an effect on CdA all the time.
My point is this. Change your position, and you change how you interact with your bike, clothing, helmet, etc. If we were to create a true hierarchy for aero, it might look something like this:
Dial in the position first, and don't make the mistake of assuming lower is always better. Once complete, you'll get better results testing everything and anything you want to put on the list.
- Helmet or wheels/tires
- Helmet or wheels/tires
- Clean front end (this could include aero bars, which may result in moving up this list quite dramatically depending on initial setup)
- Hydration/Food setup
Look, I could answer questions all day long about which skin suit is quicker than another, which is the faster bta setup; have I tested this, have I tested that. I get it, the information is addictive. In the end, and yes I know it gets old hearing it, but in the end it's all very personal. Your result may or, really, certainly WILL vary. I hope this helps.
Jim Manton / ERO Sports