Its clear to me that the 21" wheels reduce range. Whats unclear to me is why - I have asked a bunch of times in different threads but no one (that I have seen) has come out with a definitive answer. Yes the tires are more sports oriented so we can expect more traction/grip as a result. So, in the beginning one can expect a 5%+ delta between the two - that eventually reduces to a minimal impact though. So, with that in mind is the delta then more attributed to weight because the wheel cast is larger than the 19" wheel? If so, then wouldn't it make sense that a wheel in 21" that had an unsprung weight lighter than the 19" would reduce (and perhaps eliminate) the delta between the two wheels? Has anyone ever "weighed" in on this subject with comparisons or thoughts around this?