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Old 08-09-2014, 09:24 AM
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CALSE
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Default .Tire Pressures

I would like to know what tire pressures has worked well for you on the track. Please identify tire size/manufacturer/cold/hot:

245/35/20 Pilot Sport Cup 2: _ Cold & _ Hot
305/30/20 Pilot Sport Cup 2: _ Cold & _ Hot

I will update above once I finish my break-in period.

Last edited by CALSE; 08-11-2014 at 04:17 AM.
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Old 08-09-2014, 11:53 AM
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SamFromTX
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You won't get a consistent answer.
I used to find hot F/R 28/29 as optimal but with further tweaks, F/R 29/30 works best for my setup.
Cold temps will vary greatly, based on how "cold" are the tires, ambient temp, your style of driving etc. Also, the best tire conserving strategy is to to bleed a little at a time until you get to the correct pressure and not start too low. The impatient strategy, which is what I use, is to start very low, hoping to get to target pressure by the end of sessions. In 50-80 degree weather, I have found about 10 PSI difference to work for me so my cold start temps are ridiculously low at 19F and 20R.
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Old 08-09-2014, 12:20 PM
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Originally Posted by SamFromTX View Post
. In 50-80 degree weather, I have found about 10 PSI difference to work for me so my cold start temps are ridiculously low at 19F and 20R.
Sam, I'm surprised you haven't slipped the tire or stripped the bead by starting off so low. I was lazy one day and started low (but nowhere near as low as you suggest) and my session ended quickly with a flat. When we took a closer look, I had stripped the bead on the tire. We were able to glue it back together so that I can limp home.
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Old 08-09-2014, 12:30 PM
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I ran 30F / 32R (hot) at my first trackday with the car yesterday and it felt good. Iĺll try a little lower on Monday.
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Old 08-09-2014, 12:39 PM
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SamFromTX
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Originally Posted by ranger22 View Post
Sam, I'm surprised you haven't slipped the tire or stripped the bead by starting off so low. I was lazy one day and started low (but nowhere near as low as you suggest) and my session ended quickly with a flat. When we took a closer look, I had stripped the bead on the tire. We were able to glue it back together so that I can limp home.
I haven't lost a bead yet but the outer shoulders do suffer from leaning hard on them before pressures build up. Grip builds up before pressure is optimal and that is when the worst assault on my tires happen.
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Old 08-09-2014, 09:21 PM
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Mike in CA
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For the last generation Sport Cups I had a booklet from Michelin and they specifically recommended 32F 36R as the optimum hot pressure both for track and autocross. I've yet to find a similar recommendation for the Sport Cup 2's. Had my first autocross today with the GT3 and a similar pressure range gave me my best times. The tires definitely gave up grip with higher pressures than 32/36 and too much below those pressures I wasn't as quick.

I'm no expert, but running hot pressures that are below the cold pressure (29/33) recommended by Porsche for these tires would personally cause me concern.
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Old 08-10-2014, 05:26 PM
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SamFromTX
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I went to track today (temp was 100) and ran 3 sessions. Because of the many posts about higher pressures, I experimented. The second session, I ran with hot tire temps of F/R 32/34. Terrible grip and 1.2+ second slower in a 1.7 mile track. I'm back to F/R 29/30 hot for sure. Interestingly, a friend of mine called Pirelli regarding the Trofeo R hot pressures on track and he was told 26-28. I realize they have a much stiffer sidewall so I wonder if the SC2 is different than SC. Obviously, others have different experience so as I think one will have to find what works for them.
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Old 08-10-2014, 05:29 PM
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Mike in CA
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Good feedback, Sam. I would like to find some specific info from Michelin on what they recommend for the SC2s.
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Old 08-10-2014, 05:32 PM
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Me as well, Mike. I just don't know where to start and I am reluctant to just call the regular Michelin toll free number because I don't know if I will be given accurate information or not.
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Old 08-10-2014, 05:33 PM
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Mike. On the track we never run anywhere near the manufacturers pressures especially for the rear. For example on the 993 on 18" the factory say 36/40 at 20C. On the track most 964 and 993 owners are aiming for a hot pressure around 30/32 or often 30/30! Too much pressure in those rears and they will act like balloons.

AutoX is different from the track tho as you need to set the pressures closer to target at the beginning I suspect.

I dont believe the 991 GT3 is as sensitive to pressures on the track as my old 993. I have only had one session at the track in the GT3 but felt it handled ok in the 30-34/34-36 range. I will however be targeting something around 30/34 next time out and bring those gradually down during the day to closer to what Sam is suggesting.

Mike how was your autoX experience? How did you find the car?
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Old 08-10-2014, 05:35 PM
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Please share any info you get. Michelin should produce data on the optimal temperature of the carcass. You would need to translate this to PSI based on 1 psi = 10C rule I guess and of course will depend on the camber you are running and how even you have that tyre surface and core temp...

Last edited by Macca; 08-10-2014 at 05:51 PM.
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Old 08-10-2014, 05:44 PM
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Originally Posted by Macca View Post
I will however be targeting something around 30/34 next time out and bring those gradually down during the day to closer to what Sam is suggesting.
I'm gonna have to do this as well and get over being impatient on my first session. I shredded the outside shoulders of the rear tires, while I still have quite a bit of tread. My guess this happened from leaning on them hard when they have very low pressures in the first 2-3 laps. Also, if your negative camber in the back is close to the front, 1-2 PSI difference between front and rear may be ideal. (I have 1 PSI difference now while in the C4S and TTS I had 4 PSI difference F/R).
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Old 08-10-2014, 05:49 PM
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Sam thanks for sharing.
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Old 08-10-2014, 05:55 PM
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Originally Posted by TRAKCAR View Post
Sam thanks for sharing.
You bet. I'm gonna post pics of my tire shred to get opinions.
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Old 08-10-2014, 06:11 PM
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Here are pictures of the rear tires outside shoulders and tread of right rear. Tread is fine and the shredding is not extreme but certainly there. Does it make sense that this is from leaning on an under inflated tire early on in the session or is there another reason? I have plenty of rear negative camber (around -2 degrees and forty some minutes). Again, driving with higher pressures decreased grip. I welcome opinions.
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