I have 245/45/17 and 285/40/17 front and rear - on a 8" (F) and 9.5" (R) rim. I think the tyre sizes are pretty typical for 17" - Just had a quick look and the next size up I could find in a 17 was a 335 /35 /17, gives you an overall diamter of 666 (not good if your superstitious perhaps). There is probably something inbetween but I couldnt find it on my quick look. (edit - obviously there is 315/35/17
) Cant comment on 15" sizes but 60 front and 50 rear does ring a bell for some reason.
Cheers
Edit - Also I think the bigger overall diamter you can get looks best to fill the gaurds as much as possible.