Questions on Size and Conversions?

In terms of mm's, what is the right size to simulate lug nuts for truck rims. I am confused as to what would be right for say a 3/4 " nut and a 1 1/4 " nut. The upsize is 1/25 th. and 1/35 th. scales. Any comments , thanks

Source: http://cs.scaleautomag.com/SCACS/forums/thread/1000528.aspx

Sebastien Buemi Luiz Bueno Ian Burgess