Wheel size: 18" (my street wheels are 19")
Wheel type: Factory Boxster S (1 set) and Cayman S (fronts only)
Tire size: many, but usually either 225/40 or 245/30 fronts, 275/35 or 285/30 rear
Tire type: favorites are Michelin Sport Cups and Toyo Proxes RA-1s

How often do you have to buy new tires? when I see exposed cord (?) I get my track tires used (hence the sizes and types I used) and they ususlly have only 2/32 -3/32 tread, I usually get about 4 track days on a set, or about 400-500 track miles.