Help with wheel dimensions needed

[walker]

I have a problem : I try to build my models more or less real scale.
But I have no idea what the dimesions mean that describe the tyre sizes.
Example : Ferrari 512 M 1970

front. 4.5x11/15
rear. 6.0x14.5/15

I simply need the tyre diameter, the tyre width and the wheel ( rim ? ) diameter, and I need it in millimeters. I was not able to find anything helpful .
Perhaps one of the modellers here can help.
To be honest - I don't even have the specs of my cars' tyres in mind. What for ? They are on the tyres themselves and in the cars' documents.

Roland