This is a 5.6" Diameter Curiosity rover wheel designed to fit a Pololu 12mm hex wheel adapter.
https://www.pololu.com/product/2686/resources
Scaling this model is not recommended because the hex hub will not fit the hex adapter. If you would like a different size wheel, let me know and I can scale it for you and keep the hub size intact.
(This is a modified version of Tom Croston's drawing on grabcad.com)