sounds like you have tire size confusion going on
it's not a "45 mm sidewall" or "65 mm sidewall" Say the tire size is 245/45-17. the 45 refers to the aspect ratio of the tire -- its relationship to height vs width. most high performance tires have very low aspect ratios-- sidewalls that are only 45% or even 35% as high as they are wide. this gives nice tight handling, but you are correct--those low profile skins hate potholes and ruff Maine roads.
heh, some call tires like that "rim protectors" but they aren't even very good for that, witness the many "Fuc((*&^!! I busted a wheel on a pothole' threads here on MS.
I wonder if subaru isn't straying too far from their real-world and rough-roads background by speccing such low profile tires for the regular WRX.
I mean a new WRX or STI will 110% haul ass down back roads, but what good is that if the wheel/tire combo can't handle the impacts?
not sure if 16s will fit over the 09 WRX brakes, this early in the model's history that's probly a dealer tech question. if 16s did fit, then a 205/55-16 dedicated snow makes a good setup for cratered roads of Maine.
As for 15" wheels, no way 15s will fit, unless they are $$$$$$$ dedicated rally wheels. we run 195/65-15 winter tires on the rally car, with 15x7 rims that just barelybarelybarely clear suby 4-pot front brakes. these rims run about $300 apiece. the narrow tires really offer good bite on snow or ice tho and the tall sidewalls can handle some serious hits without (much) damage.
