I'm interested in downsizing OEM MB wheels from 19inch to 18inch; however, I have the upgraded high performance brake package that includes cross drilled front rotors. The current wheel size is 19inch, I'm curious if I can purchase the 18inch standard wheels and if they will fit with the HP brakes.

 

I am using 2 sets of tires,

1. OEM for All season set: 235/55/19 tire OEM 19 rim.
2. Winter set: 235/60/18 18 alloy rim.

I bought the 20% used winter set with Michelin Latitude X-ice Xi2 235/60/18 tires for 30% of new set price.
Rim is Replika R170 Gloss Gunmetal 18x8.5 +32 5x112mm 66.5mm
https://wheelwiz.ca/products/r170-1885-44mn-32r664
AFAIK, you did not increase your rotor size 18 inch rim should work.
and no problem with the drilled holes on your rotor

 

Not sure I'd rely upon this statement absent knowing with certainty that 18"s clear the AMG brake set up, as those brakes are spoken of here as larger in size and parts catalogs make clear that some GLC come with larger sized rotors.

 

Ok, I've checked a few websites and wheel-size.com indicates that perhaps 17" alloys would work. Does anyone have experience if 17" would clear the higher performance front brake calipers?