ga41 said:
Fronts should be 225/40/18 and rears should be 255/35/18 if i'm not mistaken. The 108s are wider at the back.
You can fit the 225's to the 18 x 8.5 rears, but they will offer no rim protection and will taper in as per the picture
However, just because it can be done not necessarily sure that it should be