[JABCAT]

Originally Posted by Habber

I see some people have gone 21” rear and 20” front. Why wouldn’t they have just gone 20” all around?

They do it for appearance purposes, there's no performance benefit. If you look at owners that race/track their high performance cars, they often go with a smaller diameter wheel with a slightly taller tire sidewall. My Z06 has 19/20 factory (same as the ZR1) and many owners go down to 19s all around. Even owners of the C8 Z06 that comes with 20/21 are swapping for 20s or trying to find 19s for track use.

[MineralGreyMetallic]

Regarding 21 in the rear, 100% aesthetics.

There is so little sidewall back there.