Derfe48

Hello all,

This is just to share some experience.
Car is 991.2 GT3RS / MR alignements / Michelin cup 2
always talking about hot tyre pressure here

For a long time I drove on track with front 32psi and rear 35psi (2,2/2,4bar)
(991.1 GT3 RS before the .2)

A month ago on my local track (north of France, Croix en Ternois) I «accidently » drove with front 35psi and rear 38 psi (2,4/2,6 bar).

Guess what ? Feeling with the car was way better, I could feel the handling of ther car more precisely, I could play with some small drifts that I enjoyed a lot, feeeling was better on brake and in turns.
And last but not least lap times were better. +/- 0,5 second on a one minute lap.
Lot of turns and hard on brakes track.
(race chrono app with XGPS external sensor).

This weekend on the nurburgring I tried front 33,5 PSI and a little north of 36 PSI rear (2,3/2,5 bar). I think it was better too.

So before I was always driving with 32/35 because I found it was a consensus on this forum and when I asked someone one day at the nurbugring it was the same answer.

So what ? Am I a driver who likes higher tyre pressure ? Are people lying to keep their values secret ? Or should everybody try this ?
Of course those statements are not true true but I am just a bit confused

Few more things I would like to say :

-Kevin Estre, lap record with full Manthey Racing car on nurburgring was 33,5/36,2 PSI (2,3 / 2,5 bar) but with cup 2R tyres. Those pressure are confirmed in a video on youtube (Misha Sharoudin)
-On sunday (2 days ago) it was very hot, I was not feeling so great with the car instead of the rest of the weekend, I dropped 1,45 PSI (0,1 bar) on 4 tyres because of the higher outside temperature and fantastic feeling was back ! So I learned a small value like 1,45psi is in fact important.....
-When Manthey racing put new tyres I had my car with cold pressure 33,4/36,2 PSI (2,3/2,6 bar) and I am starting to wonder if those aren't simply the best.
- I also learned not to 100% trust the pressures on the dashboard because they can be a bit inacurrate.

Drive safe and enjoy those fantastic cars on track !
Sorry if my english is not perfect

MKIVdan

Tire pressures are going to vary quite a bit from track to track and driver to driver.

A lot of factors that come for me in Southern California is Air temp, if its hot and a very sunny day the track temp will likely be very high. I also pay a lot of attention to tire wear, if its getting close to the edge of the tread then the pressures are probably fine but if not then ill likely need to drop pressures a little more.
We also can have very cold track days that are not suited for some of the tires we run based on the tire compound. So its really a day by day basis.

Last track day i was at, ran my fastest time at buttonwillow 13CW config, pretty much a stock car with a mild alignment on cup 2. Ran a 1:56 and it was 75 degrees that day, ran 28psi cold on the front and 29psi cold on the rear to start the day. As the day went on i had to bleed out some air. There is absolutely no way I could run your cold temps of 33/36 to start the day

Derfe48

33/36 was cold tyre pressure when I got the car from Manthey Racing.
I assume they put the optimal pressure no matter of cold/or hot tyres if for some reason you go drive and do not get heat in the tyre.

In other words they put 33/36 cold but I think it's a goal for hot pressure.

marcus1982

Well, maybe for some it's a secret. I saw some on-board videos where the screen was actually on the tyre pressure window. Car handling characteristic is driver preference, but if you improved on your lap time, you are on the good track.
Did some of you tried filling 'em with nitrogen? Does it help on pressure variability?

ParadiseGT3

Comes down to driver preference, alignment settings, pace are influential factors.

I target low 30's hot on the OE tires, > 35 doesn't work for me.

Never identified performance advantage in pressure stagger front to rear, so target about equal hot pressures between all four.

Dougr743

this tire pressure debate has been going on for years. no simple answer, but one thing to understand. Unless you have tire warmers and can set your temp, prior to hitting the track, you are guessing! What you dont want to do is bake the tire. So if you run low pressure and see high tire temps, you will bake the tire and will need to add more pressure, yes more tire pressure! If you are seeing lower temps and or lower pressure you need to bleed tire pressure to increase optimal tire pressure based on tire temp. So testing tire temp is as important as pressure. This is the struggle unless you have tire warmers and get the tire up to temp prior to running, and set pressure to hot temp.

Us old X super bike racers, or anyone tracking a bike, have to deal with this, at the extreme edge. Example. if you want 180 degree tires at 32psi. You would heat the tires and set the temp, if you came off the track and tire temp stayed close to target, and pressure stayed close to target, you are maintaining steady temps, and then you toss on your warmers, set to 180 degrees and your pressure stays. If you came off lower in temp, you would be lower in pressure, then bleed air. if you came off higher in temp, and pressure, you would add air, decreasing the swing in pressure change and degreasing temp. Higher pressure usually will lower tire temps and slow tire heat exchange. Although there are variables, like ambient temp, track temp, etc. you just want consistent temps and pressure for the pace you are running and as you monitor temp, you can understand pressure

Larry Cable

https://rennlist.com/forums/718-gts-...peratures.html

Larry Cable

I'm surprised they did that - MR are pretty OCD about (hot) tire pressures and recommend around 1.9/2.0 or 2.0/2.1 bar hot for the track ('Ring) MPSC2

Derfe48

In this post I can read "Michelin and Porsche recommend 29 front and 33 rear" whereas on my side I found that Michelin says that the best hot tyre pressure is between 33.2/39 psi (2.3/2.7 bar)
See attached (Michelin's website)

It's for CUP2R but still interesting.
It's kind of funny how informations can be different.
Finally it seems that most people (from what I read on this forum) track their car with "low" tire pressure, whereas I like "high"

Derfe48

Interesting, first time I read this.

Larry Cable

@Derfe48 since you are located in France (lucky man) you should consider downloading the "GT Circle" mobile app and joining that group, where I believe you will have access to MR staff, I would ask them what temps they recommend!

they were very insistent last week at the 'Ring about running the 4RS T.P at 1.9/2.0 ...

https://apps.apple.com/de/app/porsch...latform=iphone

Derfe48

Lucky for the landscapes, mountains, sea and crazy roads, and being close to the nurburgring (3.5 hours, so far 88 laps in 2023, 199 total) but not for all the rest ! let's not go political

This app look awesome, thanks for letting me know. Damn it's not available on android !

1.9/2.0 seems very very low to me, Kevin Estre did his record lap with the MR 991.2 GT3RS with 2.3/2.5 (cup2R).
I am very surprised of such pressure.

Larry Cable

I know, and not yet available outside Europe either

could be that the R's "enjoy" higher pressures but that is what MR were setting on the PSDS cars last week at the 'Ring ...

p.s as for politics - its sh*t everywhere my friend!