All other things being equal, I’m wondering about the aero difference between a 40mm and 60mm rim. Can’t seem to find anything specific regarding rim width.
Reason I’m asking is because of recently picking up a set of used 40mm Real Design for a psalm. Just wondering how much I’m losing to the 60mm version of the same wheel.
I think you mean rin DEPTH. Width is the same as the tire. Most aero rims are bout 19-20mm wide from memory.
I don’t remember the reference, but recall reading some time that for an average cyclist (whoever he/she is) that 50mm depth is needed. Any shallower, say 40mm, the air being split by the tire/rim, doesn’t have time to re-attach to the rim, and creates alot more turbulence and therefore drag. One can reasonably assume that as the speed goes up, the rim depth needed, to allow air re-attachment would also increase. Therefore, while a 40mm rim may look aero, it may not provide much if any benefit over a standard box section rim. If you ride slower than average, then a 40mm depth rim may be sufficient.
Of course, the above statements are generalizations and may not be completely accurate for your wheel or for you and the speed you ride.
Look for information from John Cobb, the aero guru for bicycles. A search should provide some useful info as I know he’s got some good info on drink bottle placement and drag numbers etc.
“I think you mean rin DEPTH.”
Yup. My typo.
LOL (rin)
That’s what you get when a male blonde over 40 trys to type at over 50 WPM!!
Good spotting
Zipp has a convenient little graph posted on their Flashpoint site.
Thanks. That’s exactly what I was looking for. Interesting that the 40mm isn’t all that much slower than the 60mm.