I was wondering what would it take, parts and cost, to replace standard 12.6" front and 12.1" rear brake rotors with the factory 13" rotors. In a dream world, all that it would take is replacing the rotors, but I know that is highly unlikely. I was hoping that by replacing the calipers and the rotors would do the trick.

 

You will have to change the calipers as well as the rotors since the calipers are different, however its not really worth it, if you are willing to spend $$ on brakes you are better off buying the G37S stock BBK imo.

 

Riverside Infiniti sells oem replacement kit for 2k.

 

As mentioned it's a straight bolt on, but requires both caliper & rotor.

I know some have looked at these because of the tendency of the X brakes to develop shudder.
If you can find a good set of used ones it's not a bad upgrade.

IMO, if you're upgrading & buying new; the OE Akebonos from the G37S are buy far the best way to go.

 

That is some good advice on the Akebonos. However some of us just prefer the OEM parts over aftermarket. But for around $1500 someone can have a big brake kit, that is very tempting.