In Reply To:
How does one go about measuring CdA? (I'm guessing that's a measure of frontal area[?]).
Posted at Gordo's board earlier:
First, you must have a reliable powermeter (SRM, Powertap or Ergomo). Then, you must find a flat place to ride at least 1 mile in each direction without wind or traffic. Then you gather data for your bike position. Do one pair of runs at 150 watts; then at 170; then 190; then 210; etc. until you max out. Do it again until you have 10 runs for a given bike setup. I'll skip the math here -- go to biketechreview.com's forum and ask or search the d-base (it's a simple Excel calculation). You can get a rather accurate figure for CdA, with a tire rolling resistance figure thrown in for free.
With patience and a keen sense of observation, you can make very big improvements. You can't get the accuracy down to where you can tell one aero bar from another, but you can sure tell if you're gonna save 15-20 minutes in an IM. It takes an hour of work to get data for a given bike setup.