I've been browsing this set of HRE's for a bit. Maybe someone on here is able to assist.

I have a 991 C4S, which have the 20 x 8.5 ET51 and 20 x 11 ET52. The 590's listed below are 20 x 9 ET51 and 20 x 12 ET44. The compatibility chart says they won't fit.

Based on my calculation, there's an additional 32mm in the rear rim width vs the OEM (1" = 25mm + offset difference). I currently have 15mm spacers on the rear, with no rub, there's still approximately another 1/4" to 1/2" of space in the wheel well; which puts my current OEM offset at 37mm. The fronts have 7mm spacers, which puts the offset at 44, there's a little more room upfront as well.

My questions are:
Will these not work because the spokes won't clear the front calipers?
Is it an issue that the widths + offset differences are outside of the tolerance limits for the 4-wheel drive transmission?

http://www.ebay.com/itm/New-HRE-590R...690c00&vxp=mtr

 

Are you still looking for input on this?

 

Thanks! I did speak with the folks selling them, they indicated it shouldn't be a problem clearing the front calipers. But, if you believe otherwise, input is always welcome.

 

Calipers wont rub, so no worries there.
What tires brand/size;
- Do you plan to run on those wheels?
- Are you running now on your OEM wheels?

I can then tell you the exact change in outside fender clearance, from what you have now.

 

Everything is OEM. I have 15mm spacers on the rear, 7mm on the front. Still have plenty of room.

 

I ran the calculations:

Rear w/ 305-30-20 PZero:

• +0.59" w/ 15mm spacer on 11"/52mm OEM Wheel
• +0.52" w/ no Spacer on 12"/44mm HRE Wheel
  • so you are -0.07" [2mm] on the new wheel

Front w/ 245-35-20 PZero:

• +0.28" w/ 7mm spacer on 8.5"/51mm OEM Wheel
• +0.10" w/ no Spacer on 9"/51mm HRE Wheel
  • so you are -0.18" [5mm] on the new wheel

Food for thought:

Front w/ 255-35-20 PZero:

• +0.30" w/ no Spacer on 9"/51mm HRE Wheel
  • Gives you +0.02" [0.5mm]
  • This makes way more sense and matches what I have on my Sport Techno wheels.
  • I doubt 0.1" Radius will mess up your diff.

 

Thx Lunarx.

 

I can then tell you the exact change in outside fender clearance