Rich
The R888 spec sheet details

225/45 17 inflated diameter of 25" = 635mm
205/40 17 inflated diameter of 23.5" = 596.9mm
as comparision
205/50 15 inflated diameter of 23" = 584.2mm (Standard tyre size)

so your are talking 2" (50.8mm) larger diameter than std , and this data is from Toyo spec sheet.


225/45 16 inflated diameter of 23.8" = 604.5mm is maybe more suitable if 16" wheels can clear brakes. I've just spoken to Compomotive and got a brake spec sheet to fill in and send to them for confirmation if 8x16 MO will fit over my brakes.

Unless you want to mutilate your arches you really do need to consider diameter as well as width. I'm in exactly the same boat.