Ive had my arches cut back bigtime & the biggest ive been able to get on the back is 235/40/18 X 8" this gives 99% clearance even on vicious cornering. The 225/40/19 X 8" used on Topspeed runs cannot be used on the road as it rubs bigtime. My car is standard ride height. Dont consider moving from 17" on the front it destroys the handling a bit stupid when lots has been done to suspension etc. Been their done that.
Dont put looks over correct handling & correct geometry.