I suspect I already know the answer but can someone confirm for me whether or not the 993 cup wheels (17x9 - 55MM) will fit on the front of an 87 S4. Thanks in advance.

 

Sorry. No.
But you already knew that....
You could use either a 65mm or a 68mm offset, I can't remember which
fits better but either are possible. The 68mm will provide you with
1/8" more fender-to-tire clearance over the 65mm.
Also keep in mind that different tire manufacturers' identically
"dimensioned" tires will in fact vary in actual size/width, so this just
throws a bonus complication into the clearance problem.

Brad
'78 euro 5 speed
928 Owners Club
Rennlist #020804-2937
<a href="http://www.p-caronline.com/directory/showngo/" target="_blank">928 euro</a>