Will 255/40/18 fit a 2007 e350 wagon 4matic, it is 1/2 in wider on each side.

I use all 245/40/18 with AMG new ST3 front 8.5 off 38 + rear 9.0 off 39 for my estate (e200kom) avantgarde (a bit lower than normal). Just ride perfect and overall height is close to original spec. (245/45/17 with 17*8 off 38).

Thank you for responding.. the tire size I am going with is 1/4 in wider on either side

should be fine