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Discussion Starter #1
I picked up a set of 19" 987 wheels for the 981 and track days, and am going to wrap them in Pilot Sport Cup 2 tires. Having experienced understeer in the car on a 235 front, I want to up that, and am wondering what the max front width I can run is, and if I can stay with a 265 rear while upping the front without any issues.

Car
2014 Cayman S

Track Wheels
F: 8x19 ET57
R: 9.5x19 ET46

OEM Tire Sizing
235/40R19
265/40R19

Proposed Tire Sizing
245/35R19 (255/35R19?)
265/40R19
 

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I have run 245's and you can easily run 255's ( or more).
Just keep the front diameter roughly equal to or smaller than the rear to keep the PSM happiest
 

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Discussion Starter #3
I have run 245's and you can easily run 255's ( or more).
Just keep the front diameter roughly equal to or smaller than the rear to keep the PSM happiest
I worry a 255 on an 8" wheel wouldn't be ideal.

Any issues running a larger width on the front, but keeping the rear stock at 265?
 

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I've found an extra 10mm (on another mid-engined car) in the front doesn't usually upset the balance. Having said that, I've put the stock size Cup 2s on 19 inch BBS's on my CGTS and they fit perfectly.
 

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Discussion Starter #5
I've found an extra 10mm (on another mid-engined car) in the front doesn't usually upset the balance. Having said that, I've put the stock size Cup 2s on 19 inch BBS's on my CGTS and they fit perfectly.
Those look great. Have you had the C2s out on the track yet? What are your thoughts on them?
 

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Discussion Starter #7
Sounds good.

Are your plans to daily drive on them? Did you order them heat cycled or shaved?
 

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Discussion Starter #8
Also, your side walls look slimber than j was expecting for a 19" wheel. What are the widths of the wheel? And you went with the 40 aspect ratio all around? Maybe the tire just is a little shorter for the size.
 

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I would go with the 245/35R19 and the 265/40R16 in the Cup 2. In our testing they are a superior handling tire and they can be driven to and from the track. They are in stock currently. If I can help let me know.
 

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I didn't have them cycled or shaved, and got them (as always with my tires) from Tire Rack. I have them ship to my installer and love the service. They are the recommended 19 inch stock size in 40 aspect.

I got the recommended offset BBS CH-R's, but don't remember offhand what width those are. Tire Rack carries these as well, though to be fair, I got mine elsewhere because I wanted the engraved Motorsport writing and apparently the US version does not have that. I can say that the offset is just perfect for the car, IIRC it's a few millimeters less than stock so it sits pretty flush with the fenders. The sidewalls bulge a little, I think it looks good and IMO looks a little better than the stock 20 inch wheels with the very low profile tire.

I am hoping to use these pretty much everyday for a couple of months while I do some track events. I haven't driven the tire through rain, but judging from the perfunctory grooving, have doubts how safe they would be over puddles. My experience with R compound tires in the wet, other than at the track with decent drainage, is very poor. The Cayman is a second car, so I can get away with not driving if it looks like heavy rain. My understanding is these are essentially R compounds with better durability. In terms of just everyday driving, they feel terrific with all the grip you may need on the street and then some. There was initially a little road noise that disappeared in about 50 miles. Turn-in and steering sensitivity seem just fine even when cold. In that they seem light years ahead of Yoko AO48's or Bridgestone R888's that I'd use as my track/street tires on a Lotus, which felt wooden until heated up. I have no desire at all to drive theCayman on the street in those kinds of tire again.

At this point, that's all I have on these. More later.
 

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One more thing, I re-read the OP's original post, and am not sure that an extra 10mm in the front would do much for understeer. I don't know how much experience you have, so excuse my presuming anything, but what you're thinking is understeer may really just be a little lazy turn-in because of lack of negative camber. I spent quite a bit of time fiddling with the setup of my Elise, also a mid-engined car, to dial out sluggishness on turn in which was present whether I used the stock suspension fronts (175s) or the sport suspension setup (195s). What got a pretty perfect neutrality was adjusting the front vs. rear shock valving, increasing the front bar stiffness and getting -2.5% camber.I suspect much the same compromises exist in the 981 chassis.
 

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I would go with the 245/35R19 and the 265/40R16 in the Cup 2. In our testing they are a superior handling tire and they can be driven to and from the track. They are in stock currently. If I can help let me know.
I sure hope you meant 265/40R19. The 16s would be entertaining to say the least. ;)
 

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I bought the PSC2 tires in stock 19" size. I've autocrossed them twice and am disappointed in their performance. Looking at them after the latest runs I see that there's no scuffing on the inside section of tread on the rears, just a little on the fronts. It's like I'm only getting use of 80% of the tread width. I've had the alignment set to max out negative camber, so there's nothing I can do there.
 

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Discussion Starter #16
I bought the PSC2 tires in stock 19" size. I've autocrossed them twice and am disappointed in their performance. Looking at them after the latest runs I see that there's no scuffing on the inside section of tread on the rears, just a little on the fronts. It's like I'm only getting use of 80% of the tread width. I've had the alignment set to max out negative camber, so there's nothing I can do there.
i have never autocrossed, but I wonder if a short burst then lots of waiting is enough to generate adequate heat for the tire. Unlike the PSS, the C2 take some time to build heat.
 

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I am running MPSC2s 235/40R-19s in front on 8.5 inch rims and 265\40R-19s on rear 10 inch rims. Obviously, not N-rated. They work fine on my 981 Cayman S
 

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Yes, it'd be nice to have a pyrometer to check heat. I did six runs in a bit over an hour on asphalt with air temp about 85. Looking at what might be an older Michelin brochure on Pilot Sport Cup, I may be running my pressures 3-5 lbs low. I don't see how that would give me no wear on the inside but I'll try higher pressures next time.
 
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