I have a 2001 slk320 and like to buy new rims and tires. The excisting tires are front 205/55 R16 and rear 225/50 R16.
Front 225/40 R18 and back 255/35 R18.
Will i have enough clearence for brake lines?
As the front tires are wider, will there be enough clearence between the tire and the body when making tight corners?

 

I forgot to mention that the second set of wheels front 225/40 R18 and rear 255/35 R18 are the new ones I like to install

 

Presumably the car hasn't been lowered?
The tyre sizes are correct. Check that the offsets are correct though.
I ran the same sizes before (16") and after (18") without problems and ride and handling are both good - now Continental tyres on Carlsson style rims. My front guards were rolled to prevent them rubbing on the tyres. See my phto gallery for pics of how the car looks before and after.

 

I also run the same size tyresa on 8.5 x 18 and 9.5 x 18
35 and 38mm offset

Bazzle