I want to buy a second set of wheels so I can rotate between winters and summers easily. I found a good deal on FB marketplace for some XXR 530's but they are 18in rims. I know some 18's will clear the akebono brakes on the S models, and some need spacers. My question is, does anybody know if these will fit? Does the g37s sedan have the exact same brakes as the coupe?

 

What's the width and offset?

Calipers clearance is more about the wheel face/profile of the specific wheel, there are 19 inch and 20 inch that won't clear the Akebono.

Example:
Enkei RPF1 18x9.5 +38 won't clear
Gramlights 57CR 18x9.5 +38 will clear

Both have the same widht and offset but difference clearances.