First, thanks for all the info so far.

I put the wheels I purchase on my X - the difference in the look of the car is huge! I'm leaving the original tires on the wheels for now - they don't have a ton of tread left, but I'll replace the tires in the early Summer.

The current tires are Michelin Diamaris, with the exact specs that Twins quoted above. The tires say max pressure of 51 pounds (which seems very high), but what do you think would be the optimal tire pressure for these tires? The tire pressure on the door sticker is stated for 17 inch tires.