Originally Posted by
79pmooney
Narrower being lighter and narrower being less frontal area is handwaving? OK, I guess the world isn't what it seems and that what I learned engineering school is BS. (We learned that wind resistance equaled frontal area (for a rim/tire ~= height times width) times coefficient of drag and velocity squared. So a narrower rim/tire of the same coefficient of drag would yield a lower wind resistance. Guess I have to go back to school to learn what is really happening.
It’s hand waving to say an unquantified reduction in area or weight will offset an equally vague reduction in rolling resistance. On the other hand there’s lots of data for a wide range of specific cases where wider, lower pressure tires test out faster.
Your description of drag is incorrect. It’s left to the reader to find the error.
There’s no reason to believe changing the tire width will not affect Cd. In fact, the data show just to opposite.