Max Wheel Size???

[turbom395]

I have a 95 M3.
suspension: H&R race w/Koni
I am looking to place some 18"

there is a set of wheels for sale with these specs:
front: 18 x 8.5
offset: 40mm

rear: 18 x 9.5
offset: 35mm

Do you guys have any experience with these specs?
and what tire can be fitted?

thanks
alex