largest 18" tyres that won't rub

[DFreeman]

I have an '06 Z4 Coupe with the 18" M alloys - 18x8 front and 18x8.5 rears. Can anyone tell me what sizes I can go up to without scrubbing the tyres? Research I hvae done so far seems to indicate that 235/35-18 front and 265/30-18 rears should be fine, but is there a slightly wider option on 18's that will fit ok?
Thanks​

 

[jnrdavo]

just remember, may give you better grip in the dry, but worse in the wet ;-)

 

[DFreeman]

Yep, will do thanks jnrdavo