Run4Red

Just did first HPDE in recently acquired 2015 Cayman GTS. Instructor (yes, I'm green) suggested upgrading my stock Pirelli P Zeros to street/comp tires to allow higher cornering speeds. Trouble is, Tire Rack shows NO street/comp tires for the GTS (front 8.5x20 235/35, rear 10x20 265/35), and only 4 Max Performance Summer tires.

Question is, can I go to a 19" or even 18" wheel to increase tire selection? 20" is the only factory wheel size for the GTS. Since 19" and 18" are not options, what would they do to all the electronics, like antilock, PTV, PSM, etc. It was suggested to me that they might not function correctly with non-factory option size wheels/tires. Anyone know?

If that fails, would Michelin Pilot Super Sport tires support greater lateral G-forces, i.e higher cornering speeds?

PCarOMFS

I plan to run MPSC2 245/35/20 front and 295/30/20 rear on OZ Leggera 20x8.5 front and 20x10 rear. You don't necessarily need to go that wide in the rear, in fact it may induce a little more understeer. You could also stick with 245/35/20 front and 265/35/20 rear. I wanted a wider tire in the rear for extra grip and also to cover the 10" wheel width.

The MPSC2 should give you the grip you're looking for. You must be careful because they will not give you as much audible warning they are losing grip as the stock street tires will do. You'll have grip and the next thing you know you're spinning. You just need to get a feel for the tires' limits with experience.

Run4Red

I like the MPSC2, but as you said, you expect a little more understeer with your 245 front, 295 rear. I'm afraid going to 245 front and sticking with 265 rear might induce more oversteer. I do not particularly want the car to be less stable, even if I get more grip, at least not at my current level of experience/skill.

I'm now thinking of going to 19" wheels with MPSC2s. There are better size options for 19" and it looks like I can stick with 235 front and 265 rear for now, and maybe go to 245 & 275 F/R in the future.

I'm having an interesting time matching wheels to the OEM offset. Is there a rule-of-thumb on how much I can differ without impact?

BTW; my original post was incorrect, in that 19" wheels ARE an option on the Cayman GTS.

kisik

If you are in Green, there is no way that the tires would be your limitation. More coaching, smoother line, and right tire pressures. Yes, super sports are more popular tire but not at the point where you are in your learning curve.

--------
05' C2S

Run4Red

Speaking of tire pressure, I started at 33lb in the p Zeros, and let out air at the end of each session, as needed (while hot off track), to bring the pressure back down to 39lb. I was told to keep it below 40lb. Does this seem reasonable?

BTW: you'll get no argument from me about seat time being my biggest limitation.

arter

38-40psi should be good when hot, especially if you don't have much negative camber up front (higher pressure reduces edge wear somewhat).

As a novice, I wouldn't jump to MPSC2's yet as they are really R compound tires. Too much traction will slow your learning curve.

I would suggest Michelin PSS's ( Super Sports) as a nice step up, 235 or 245's in front and 265 or 275's in back. A 245/265 combo will work quite well, but the 235/265 or 245/275 combo's match slightly better. The PSS are very nice road tires too.

Run4Red

Thanks for the pressure feedback and tire advice. Sounds like sage advice. Guess I'll wait a while (more experience) before worrying about upgrading tires. I ran Michelin PSS's on my Boxster and liked them, but what do I know Camber is whatever the Cayman GTS came with. I've done nothing to the car as of yet, and other than tires, have no near-term plans to change anything. Like you have all been saying, learn to drive first.

cgfen

as long as the overall effective diameter is the same +/ - 3%, you should be good to go with 19" wheels / tyres

consider
Yoko AD08R
Hankook R-S3
and Michelin MPSS

as tyre alternatives.

Make sure any new wheels clear your calipers / rotors

Have fun, even "new guys" can benefit from dedicated DE wheels.

Craig

Rob996

Please do not buy R-comp tires yet.. As others have said stickier rubber will hamper your learning curve. More and more driving clubs including some PCA chapters are not allowing green and novice students R-comp tires on the track.. Which I fully endorse.. Run through a few sets of street tires first, with the Michelin pilot super sport as a great tire.. BTW, a smooth driver could be very fast on track with these PSS's..

As you will discover over time this sport can suck you in.. Stickier tires means getting better brakes, and now with tires and brakes you need to adjust or change the suspension.. Oh let's remember safety , maybe ahead of the others. Harness, seats, roll cage.. Etc..

It's a blast.. Take your time and enjoy yourself.

Surfer161

I was at tech tactics East this weekend and had a private conversation with the Michelin engineer

he said that to get the best performance from the cup 2 tires, keep HOT tire pressure near 34 psi. if it gets a bit slick, move it down to Porsche recommended 31 PSI HOT.

He recommended running 4-6 hot laps in the first run group, pulllng off and bleeding air out - with a pressure guage, do not trust TPMS readings.

and if you are driving them home, REFILL them before you leave the track.

ExMB

OK, who put on that HPDE? Non of the PCA instructors I know will ever suggest to a green student to get comp tires. There is way to much for the student to learn before he should go there.

Run4Red

After a half dozen different instructors, I don't know what that first was thinking. All others said I need to work on driving skills before I start upgrading car. And it seems the more I learn, the more I know I don't know. I'm still green in one region, but have been promoted in another. I am switching to MPSS and 19" wheels, since my original Pirelli's are shot and 19" gives me better tire selection.
I was also told by a Michelin tech re the MPSS; "36-38 psi hot should put you in the optimum range for HPDE".

JayG

Look at Dunlop Direzza ZII Start Spec as a great street/track/AX tire
Don't know if they come in your sizes.
They are just under Potenza RE-71's in grip and better than MPSS or MPS2
They have been one of the hot tires for a few years now and now the RE-71 is the hot tire

I have MPSS as my DD tires, they are not as good as others for track use. I currently am using the Star Spec for track/ax and will probably go with RER-71 when they wear out

My car is bone stock BTW

Michelin tires are not necessarily better than others, just more expensive, although they do have world class customer service and actually have tread life warranty on most tires. The only reason I have MPSS as my DD tire is they were free!, otherwise I probably would have gone with Sumitomo HTR ZIII which are around 1/2 the cost of MPSS and perform really well. I have tracked the HTR ZIII's and they were not bad at all . My Star Specs are a few seconds faster

As others have said, do not get R-comp tires. You will need to do other mods like suspension to really take advantage of them and with a stock suspension, you can really get more than .7 deg neg camber on the front and you need lots more with R-comps

Run4Red

On Tire Rack, the ZII only have 2 sizes, one 17" and one 18". So even if I went to 18" wheels they would not have the front/rear sizes. The RE-71R do come in Cayman sizes, so they would be worth looking at when my current tires wear out. Similar to you, maybe MPSS for DD and RE-71R for DE/track.

I've received similar advice re R-comp tires; I'd need to beef up brakes and suspension. I'm trying avoid starting down that slippery slope.

ExMB

At your stage I wouldn't recommend the RE-71s until you've done some mods. They need more camber and will wear a lot faster.