BREMBO 18ZR, Golf R

[fatvdub]

Just picked up these calipers for pretty cheap. I haven't searched in the right spot yet. But...
From what I've seen so far people are using the Mercedes rotors. Why? Ours are 345mm vs. 350mm...
Is it how they are orientated to the wheel and caliper? Or...

 

[GIACUser]

yes, however the calipers can be machined to accept the offset of the 345 VW Golf R rotors with the proper bolt kit. That is what I ran on my MKV GTI. I purchased mine from Rotorlab (Link to explanation of mod necessary for the 345mm)

Pic of my old setup