I have 6" wide on the front and 7" on the back.

The car had a set of GT radial 205 50 15s on the back and looked a little small for the car.
They had flat spots on them so I replaced them with 205 50 15 Dunlop Direzzas and they look even smaller and stretched.
Not too happy about the looks. Should have done some research first.
I have 195 55 15 on the front and they look fine.