Some info for the collective.
Having moved to Vermont, I needed a snow tire package for the 1999 996. Originally was going to go the usual route of buying a package from Tire Rack but the thought of another stack of tires/wheels in the garage ...
Realized that I had a set of Cayman wheels from a 2007 base Cayman. To make a long story shorter, they work if you put 10 mm spacers on the front and get some 60mm lug bolts for the front. The rears are fine just they way they are. Both front and rear will have 7 threads of engagement.
Summer tire/wheel setup:
F: 7x18 with 205/50 -> 26.1" dia
R: 9x18 with 255/40 -> 26.0" dia
Winter tire/wheel setup:
F: 6.5x17 with 205/55 -> 25.9" dia
R: 8.0x17 with 235/50 -> 26.0" dia
You get the benefit of a narrower tire (better for snow), and a taller sidewall for better pothole survival.
