Gcracker07110

Would these would not fit 991 C4S?

Front: 8 x 19 57mm 235/35/19
Rear: 11 x 19 51mm 295/30/19

CSK 911 C4S

Here's some spec's from the Suncoast web site for 19"s on the C4/C4S for comparison.

Size: Carrera 4/Carrera 4S
Front - 8.5 x 19 ET54 - 235/40 R19
Rear - 11 x 19 ET48 - 295/35 R19

RobC4sX51

The wheels will fit fine, I have them on my '13 C4s cab with Pirelli winter Sottozero tires in the sizes listed above by CSK. You need the 40F & 35R profiles to keep the ratio (speedometer and AWD system) more in line for the 991. Oem offset for our cars is 51F & 52R, so I used and recommend 5mm spacers up front which gives you 52F & 51R. Very close to oem specs and actually looks nice with the 235 & 295 tires for winter. Hope this helps. Here is a side pick of mine but doesn't really show the tire clearance but it's great.