Porsche used endless variations in offset for different cars, not to give wheel manufactures something to do but to find the optimum specification for particular cars and particular applications and when contemplating any change the factory specifications should be the place to start. The table below gives the main 17 and 18 inch variations. Note the weight saving of the standard RS wheels!
|17” Style||Width||Offset||Part number||Weight|
|Cup 1||7 J||55||965.362.124.00||9.3 kg|
|7 J||55||965.362.124.01||9.3 kg|
|7.5 J||65||965.362.124.05||10.6 kg|
|8 J||52||965.362.126.00||10.0 kg|
|8 J||52||965.362.126.01||10.6 kg|
|9 J||55||965.362.128.00||11.8 kg|
|9.5 J||68||965.362.128.05||12.5 kg|
|964 RS Cup 1 Magnesium||7.5 J||55||965.362.124.15||8.5 kg|
|9 J||55||965.362.128.10||9.3 kg|
|Cup 2||7 J||55||993.362.124.00||9.0 kg|
|7.5 J||63||993.362.124.05||9.4 kg|
|8 J||30||993.362.126.02||10.1 kg|
|8 J||70||993.362.126.01||??.? kg|
|9 J||55||993.362.128.00||10.15 kg|
|9 J||70||993.362.128.01||??.? kg|
|18” Style||Width||Offset||Part number||Weight|
|964 Cup 92 (Speedline)||8 J||52||965.362.136.00||?.? kg|
|9.5 J||47||965.362.138.05||?.? kg|
|964 Turbo 3.6 (Speedline)||8 J||52||965.362.130.0||11.54 kg|
|10 J||61||965.362.140.0||12.16 kg|
|993 RS (Speedline)||8 J||52||993.362.136.81||12.5 kg|
|10 J||65||993.362.140.81||13.5 kg|
|Turbo I (hollow spoke)||7.5 J||50||993.362.134.05||8.6 kg|
|8 J||52||993.302.136.00||8.9 kg|
|10 J||40||993.302.140.00||11.4 kg|
|10 J||65||993.362.140.01||10.6 kg|
|10 J||65||993.362.140.01A||10.86 kg|
This list isn’t exhaustive and of course doesn’t show any after market wheels.
Note that Porsche themselves do not recommend fitting 18” wheels to the 964 and variants but did do it on the last of the 964 turbo’s and the 3.8RS. On these cars it is common to see the steering rack brace used on the 993’s to counter the additional load of these wheels.
The commonest replica wheels are the Mille Miglia, looking a these in comparison with the standard wheels:
An RS on standard 17” wheels has an offset of is 55mm on both the 7.5” and 9” x17 wheels.
The original Cup cars had wheels of 8×17 and 9.5×17, with an offset of 52mm and 68mm respectively. They also had 21mm spacers at the rear (giving an effective offset of 47mm.
Mille Miglia replica wheels have an offset of 55mm front and 47mm rear which moves the wheel outwards , (meaning if you have 20 or 21mm spacers they won’t fit – more on spacers later).
For the later Cup cars with 18” wheels the offset is 52mm front and 47mm rear.