The Mad Hatter

Am needing to get a new set of wheels for my classic impreza with wide arches and have considered fitting wider wheels on the back than the front as the arches flare out more.

Having done a bit of research I figure that fitting 225x40x18 front and 255x35x18 rear tyres with 8" front and 9" rear wheels would give approximately the same rolling radius.

Has anyone ever done this what sort of effect might it have on how the car handles.

If I dont fit different sized wheels then the offset would need to be different front and rear and how would this affect the handling.

Any help is much appreciated.