EuroDriverSD

I apologize in advance for asking a potentially dumb question but I tried searching which turned out to be a dizzying endeavor with no clear answer for me.

I have a set of wheels that I want to throw on my newly-acquired W204 (2013 C300 4Matic Sport) for a square setup.
The wheels are 18x8.5 and have a standard offset of ET50. I have asked the manufacturer for a set of spacers and corresponding wheel bolts and they are suggesting the following:
Front: 5mm spacers
Rear: 10mm spacers
With that configuration, I will end up with:
Front: ET45
Rear: ET40

I think I have room for a bit more offset to have a more flush look. I also want to go with the tallest tire possible and I am considering either 245/45/18 or 255/40/18 size.

What are your recommendations for optimal offset and tire size?

Much appreciated.

S70Houston

See if this may help you. It helped me when selecting wheels and offset for my wife’s GLC

https://www.wheel-size.com/calc/?whe...cl=30mm&sr=0mm

EuroDriverSD

Thank you. I will explore it and make my decision.
Brabus indicated offset of ET45 in front and ET40 rear - basically said it's the only configuration option they will offer me.

S70Houston

Here is what I also found, shows the wheel sizes and off sets the C300 was delivered to the US

2013 Mercedes-Benz C-Class - Wheel & Tire Sizes, PCD, Offset and Rims specs | Wheel-Size.com