I was told that the Cup 1's came off the 928S and that for 928's, they are rare in their own right.
The 7.5 J front Cup 1 and Cup 2's are a slightly different inset from the 7.5 J Mags of the 964RS --- 65mm on the Cup 1's and 63mm on the cup 2's whre the mags are 55mm --- all the rears, that is cup 1, cup 2's and mags are 9 J with 55mm insets.
Hence on the 964RS the front are often used with spacers to pull them out by the 8m difference --- in practice 15mm spacers work very well on my 964RS.
But these are the demand drivers for the older wheels.
The Mille Miglia Cup 1's are spot on for the front --- 7.5J and 55mm inset, and fill the rear arches a little better with 9J and only 47mm inset for the rears, but they are heavier by .7KG front and 1KG rear over Cup 1's. They also did Cup 2's in the same sizes which weighed about the same as the Porsche Cup 1's.
The BBS 18" as a compromise is good (Carrera from Facelift Boxster 986) 7.5J inset 50 and 9J inset 52 weighing 9.3Kg front and 10.3Kg rear --- within a whisker of the Porsche 17" Cup 2's .... and reputedly worth 2 seconds a lap on the Porsche test circuit over 17" wheels due presumable to the size of the tyre contact patch. But, on the road 18" obviously has less tyre wall suppleness than 17" !
I hope this doesn't muddy the water too much [
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