Well, I know a person that has a C36 with those wheels. He has the 18x10's for the rears.
He said he didn't need spacers to clear his front or rear brakes.
The rears defintely were too wide, but he had to roll his fender. It still rubbed though on the outer fender.
It looked good though.
I beleive the C43 and C36 OEM wheels have the same offset and size, so I would think this info would apply to a C43 too.