Posted By The Real Han Solo on 02 Feb 2014 09:42 AM
Posted By Old Rallyist on 02 Feb 2014 12:17 AM
Shouldn't need to pinch the RS3 all that much on a 987.2 Boxster/Cayman in that there are stand alone optional 8.5x19 front and 10x19 wheels. Now using the + or - 1" rule there is a possibility of having 8.5x18 and 10x18 wheels with 35 versus 40 aspect ratio tires to provide more acceleration. Will it allow the Porsche be competitive against a C6 Z06 Corvette in A Street? I doubt it but it might make things a bit more interesting. There are even wheels available with the correct offset.
True for 1st gen Cayman S? If so, that's news to me...
From Cayman Manual:
Cayman S: Front 235/40 18 -- 8x18" wheel -- 57 mm offset -- 58.5"/1486 mm track
Rear 265/40 18 -- 9x18" wheel -- 43 mm offset -- 60.2"/1528mm track
Of course the 19" wheel was optional for the Cayman S but we've found the mass and weight not helpful. The 18" wheels seem to work best. I went with the 285 x 35 rear and 245 x 40 front RS-3.
No pinching and I know I'll have clearance on the struts with a 1/4" spacer.
You can put a 305x18 rear and 285x18 front Hoosier on this car with no rubbing but it appears the RS-3 has squarer shoulders.
Yes, it's also true for the 2006 Cayman S. Although Option Code XRR (19x8.5 ET55 / 19x10 ET42 wheels) wasn't available at the car's launch, it did become available later in the model year, as the following Porsche press release confirms ... see the top of p. 5, where it describes the sizes of the wheels.
As it happens, I ran both 18x8.5 / 18x10 and 19x8.5 / 19x10 wheels back-to-back several times last year on my 2006 S (255/35-18 / 275/35-18 ZIIs on the 18s and 255/30-19 / 275/30-19 AD08s on the 19s) and it's been my experience that the 19s are consistently a few tenths quicker. I suspect the reason for this is that the 30-series sidewalls favor my pitch-and-catch driving style better the 35-series sidewalls, but I wasn't able to do enough testing to sort this out before I blew the engine last November. (Of course, with the AD08R replacement for the AD08 being a TW180 tire, this is only true for 2014, as the 255/30-19 and 275/30-19 sizes aren't available in any other potentially competitive tire.)
As for the 19s being heavier than the 18s, this will depend upon which wheels and tires you use. My 19s are Champion RG5s and the set of four (with tires) weighs over 15 lbs less than the 18s, which are OZ Alleggeritas, one of the lighter 18s available with the correct size and legal offset. Shortly before I killed the engine, I bought a used set of 18" Champion RG5s to run in 2014 and the set of bare wheels (I never got around to mounting tires on them) weighs roughly the same as the 19s (the fronts are actually a bit lighter, but for reasons I don't understand, the rears a bit heavier, so it evens out.) So unless one has the means to order 5 pairs of custom-spec'd TSW T66-F rear wheels (or is willing to run spacers to reduce the offset of the 18x10 wheel they sell off the shelf), it appears that the 19" RG5s will be the lightest wheel/tire combo that are reasonably available in either diameter.
Lastly, it's my opinion that the Caymans aren't going to fare very well in the new A-Street against the Corvette and S2000s, at least on slower, tighter courses. IMO, their too-tall second gear (74 mph!) puts the engine out of its powerband at corner exit on too many courses and the non-defeatable PSM / ABS doesn't play happy with tire-diameter staggers that vary much from OEM...