C230 17x8.5 tire size
 

Kind of a two part question, first, I found some 17x8.5 wheels I like but I’m not sure how well 245/40-17s would fit all the way around. I see people recommending 225/45-17 for front tires but I don’t think they will fit on a 8.5 wide wheel very well. Also, people running similar size setups, what lowering springs did you go with? I want it to still be functional on some of the tougher roads I have to drive on

Welcome Tsheltry, :)

http://www.alloywheelsdirect.net/inf.../mercedes-benz

Note: offset is also important to ensure correct fitment.
Lowering springs - eibach, h&r.
You will also need to check and possibly order replacement spring pads.
Do a search on this forum on w202 spring pads, lowering springs.... lots of info you can read thru to make an informed decision.
Hope this assists you.