Phokaioglaukos

996 GT3 with 235/40-18 front and 295/30-18 rear MPSCs.

Found two PDFs on the MPSC (too large to post here). Both say the sweet spot for temperatures is 160-220°F.

One says for road racing cold pressures should be 25F/28R and hot pressures should be 32F/36R. That seems like what I hear a lot, if the hot 36R is a bit high.

The other PDF says the same in the general guidelines, but for Porsche 996 wearing 225/40-18 in the front and 285/30-18 in the rear, the suggestion for hot pressurs is 32-34F and 37-40R. That seems high. It also says there is a big effect from front tire pressure changes: steering gain decreases 20=25% between 26-38 psi.

What do you all make of that? What cold/hot pressures do get on your MPSCs?

Carefree

Chris, go to the Michelin web page and look up what they suggest. That is a great starting point, but those Hot pressures do sound close.
I like to stay about 38R hot, otherwise they get slippery.

pranqster

I usually start out at 31 rear and 29 front for the first session. Usually the pressures will go to 37/38 rear and 33/34 front. I then drop to 32 rear and 30 front, I keep adjusting until I get to 35/36 rear and 32 front. The 35/36 numbers varies according to track conditions that day. Sometimes 35 works better than 36. I have run tires to the cords this way without problems.

KOAN

This is what worked for me last year. I've changed my alignment since then, reducing the difference between the F/R camber from 1 degree to .25 degrees. (was F -3, R -2 now F -2.7 R- 2.4) I have 800/1000 lb springs. Mid Ohio, Ambient temp 60 degrees, partly cloudy. Hot tire temps around 170-180 degrees. See how the rear sliding heated the rears more than the fronts? I expect to fine tune again this year or possibly work more on the alignment.
Anyway, you are in my ballpark:

Cold F 27 R 25
Hot F 33 R 35

Hope this is useful.

996FLT6

I start at 26 cold then adjust to 31-32 hot all around. Nething after 34 feels slippery to me. My pressures mite be not your comfort range. U have to experiment what feels best for u. I don't think there's a universal hot pressure for everyone. Mike

Carefree

Seems like it is not only "really common" to play with these HOT temps, but it is a matter of feel as well.

But there is a pretty common range that is within a few lbs. Start on the low side and work up from there, that might help.

We are getting some good weather here in the NW and tomorrow is a great track day for us to play with these pressures and other settings!

Bob Rouleau

Chris, about a dozen of us with 996GT3s and Cups found that 32F 34R Hot for the OEM sizes was the sweet spot. Over 35 lbs and grip falls off quite a bit.

Best,

KOAN

I wonder how accurate our gauges are? Mine must be 10 yrs old, and is a dial type. Also, the length of the track and the cool down lap probably could account for a 1 lb variance, to say nothing of the track temp ( sunny vs cloudy, am vs pm, etc)
Having said that, I'm going to try 1 lb less to see what it feels like.
Thanks for starting the thread. I needed something to get me through the next 2 weeks until I can get to my first event of the season.

enthusiast

Posted in the old threads for a stock 2004-2005 996 GT3 with stock tire sizes.

Michelin Pilot Sport Cup on track:

front 32 psi hot, rear 35-36 psi hot - up to - front 38 psi hot, rear 40 psi hot


Michelin Pilot Sport 2 on track:
front at 36 psi hot, rear at 38 psi hot - or - front 38 psi hot, rear 40 psi hot

Carefree

Nah, we have seen air pressures change due to North Korea and Kim Jung Ill introducing chemicals into our eco system.
We must now compinsate for such actions.

Good times!

Phokaioglaukos

Good thoughts, thanks. Giving them a try for the first time on Friday at NJMP's Lightning course.

Leigh2

My .02 worth I ran 32/35 hot. The problem is the starting pressures as they are horrible when under-inflated and cold and horrible when over-inflated and hot. If I have the chance I start them in the morning a few pounds low then bleed off pressure as they get warm to get to the 32/35.

DanH

32 hot all round works well in the British climate.