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Discussion Starter #1
Struggling with the configuration of winter wheels and tires front and rear.

Question:
Can I safely put 235/40 - 18 tires on all four corners of the car mounted to 18x8 rims with 54 mm offsets?

Background on my confusion:

I am looking to mount Michelin Alpin PA2 235/40 R18 tires on Andros Spec P 235/40 R18 18x8 as a result of conversations with local dealer and Tire Rack.

The owners manual call out is:
FRONT: 235/40 R 18 91V M+S WHEEL RIM: 8 J x 18 H2 OFFSET 57 mm 58.5 in./1486 mm
REAR: 255/40 R 18 95V M+S * WHEEL RIML 9 J x 18 H2 OFFSET 43 mm 60.2 in./1528 mm

I spoke with local Porsche dealer as well as Tire Rack and they seem to think no issues. The only issue might be a visual one.

Interestingly Tire Rack does not sell staggered wheel sizes in their winter rim/tire packages; the 'package' wheel size is 235/40 R18 at all four corners and the tires default at 235 front and either 255 or 265 at the rear. Mounting the wider tire on the narrower rim would seem to be a problem.

Additionally, it seems a lot of P-9rs put 265 winters on rear without problems

So, I am interested in thoughts on this matter

Cheers!
 

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I think you'd be much better served by running with the 987 base wheel and tire setup, 205/235. That's what I use and it works well.

Struggling with the configuration of winter wheels and tires front and rear.

Question:
Can I safely put 235/40 - 18 tires on all four corners of the car mounted to 18x8 rims with 54 mm offsets?

Background on my confusion:

I am looking to mount Michelin Alpin PA2 235/40 R18 tires on Andros Spec P 235/40 R18 18x8 as a result of conversations with local dealer and Tire Rack.

The owners manual call out is:
FRONT: 235/40 R 18 91V M+S WHEEL RIM: 8 J x 18 H2 OFFSET 57 mm 58.5 in./1486 mm
REAR: 255/40 R 18 95V M+S * WHEEL RIML 9 J x 18 H2 OFFSET 43 mm 60.2 in./1528 mm

I spoke with local Porsche dealer as well as Tire Rack and they seem to think no issues. The only issue might be a visual one.

Interestingly Tire Rack does not sell staggered wheel sizes in their winter rim/tire packages; the 'package' wheel size is 235/40 R18 at all four corners and the tires default at 235 front and either 255 or 265 at the rear. Mounting the wider tire on the narrower rim would seem to be a problem.

Additionally, it seems a lot of P-9rs put 265 winters on rear without problems

So, I am interested in thoughts on this matter

Cheers!
 

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Personally, I stick with stock wheel widths/offsets and OEM tire sizes. I find it surprising that either a Porsche dealer or Tire Rack would advocate putting 235 front and 255 or 265 rear on the same width rim.
 

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Discussion Starter #4
I think you'd be much better served by running with the 987 base wheel and tire setup, 205/235. That's what I use and it works well.
Thanks Spec-Al. Are you running a Cayman or a Cayman S? My car is a Cayman S. In the owners manual, your set up suits a Cayman on 17 inch wheels but is not called out for the S.
 

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Discussion Starter #5
I agree. That pretty much sums up why I pose my questions. I need a bit of validation.
 

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I run the base boxster/cayman setup on my 987.1 Cayman S. It works fine, you just need to run a small wheel spacer up front to clear the brake caliper. I think the recommendation in the manual comes mostly from Porsche wanting the S cars with more hp to have more tire, but in the snow, skinnier tire to cut through the snow tends to work best and I haven't had any issue with mine. Good luck!
 
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