Originally Posted by
RChung
Hmmm. Does this mean you *have* measured your CdA with coast downs, or are you giving reasons why you *haven't*? For the record, I do this as an athletic and leisure time activity, too -- but even were that not so I'm not sure why it is relevant to this discussion.
It is relavent (in my mind at least) because you gave no explaination as to why you need / want this information. I hope it is more than intellectual curiosity. I have not bothered to do such a test because I don't care what my CdA is one little bit. From plenty of riding experience I know my hiracer bent has a signficantly lower CdA than any of my DFs do. Exactly how much better is a detail that doesn't concern me. For most of us with limited time and money to devote to our leisure activities, the time it would take to determine CdA would be better spent doing a hard training ride (assuming the ultimate (though indirect) goal of such a coast down test was to go faster). Once I have my CdA determined with painstaking accuracy, what do I do with that info exactly? If I am trying to understand the effects of a particualr aerodynamic enhancement (fairing, disc wheel, whatever), a reasonably well done coast down test with and without the enhancement will reveal the relative improvement of such an enhancement, and that is ususally more than enough info needed to make a decision about whether to use that particular enhancement on a given ride / event.