gamma300C

I have "Searched" and members say a 235/40-18 tire with 45 offset will fit my 09 C300 Sport but when I feel for the top clearance between my stock 17 inchers with the stock 225/45-17 Michelin A/S 3 in front,, there seems to be only a 3/4" space between the strut perch and the inner top of the tire. Can someone confirm there is, in fact, room for the 18" setup ?