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chuck911 - gd insight, and thanks from a lurker, I appreciate the advice

chuck911

Tire pressure is a really simple subject made almost incomprehensible by the sheer volume of nonsense that's out there. Even though I learned all the basic info in my first post a good 30 years ago, it still came as a surprise to me when doing autocross fun runs one day my car started skating around and I was running slower even though I had the course down and the car felt super-responsive.

Well of course the car felt super-responsive. That's always how it feels running high pressure! But responsive does not equal fast! In spite of what I knew I had fallen into the trap of the repeated ad nauseum BS to set your pressure cold and leave it alone. So as the day went along my tire pressure kept rising until, around 42 or so, skate city!

For the vast majority of people, the vast majority of the time, tire pressure is nothing more than a way to fine tune how comfortably the car rides or how quickly responsive and lively it feels. Most people street driving will never work the tires hard enough to get them hard and skatey, certainly will never learn about traction by being competitively timed, and so they are able to get away, typically their whole lives, never really understanding what's really going on. But you buy a Porsche, its such a precision driving instrument you almost can't help but notice even if you never go near a track, and people start asking questions about things like this they probably never thought about much before. Its a whole new world.

So welcome, and glad to be of help.

Penn4S

Great info thanks to all. This is how this forum is supposed to work. Sounds like I'm on the right track. My butt and experience told me I was but I really like hearing affirmation from this community.

woodranch

Why not go 36 - 44 like the door label says

lunarx

31F / 33R Cold.
Its as low as I can go, below Comfort Standard Load Settings, and not get the TPMS warning.
(I would go a bit lower if I could.)
Keeps me from needing to bleed pressure at the AC or Track.

My tire wear is excellent and very even BTW.
12K+ on MPSS and still going (probably to at least 16K).

My responsiveness is fine too. The wider ST wheels (which stiffen the sidewalls) are probably helping in that area.

Just letting you know what has been working for me.
I didn't like the feel of the car at higher pressures.

lunarx

Isn't that Full Load > 150 MPH?

There are other recomended settings (in OM and MFD) for Standard Load <150 MPH which is the range where most of us drive.

Penn4S

That is full load, meaning passengers, frunk full, etc ride is hard and wear can be inconsistent. If you set at Comfort S setting the lower values are well in the proper range.

RobC4sX51

+1

chuck911

What nobody mentioned, 36/44 is an 8 psi differential. Porsche has a long history of doing things like this to alleviate the handling (read: liability) side effects of being rear-engined. Another big one is excessive front brake bias. Every manufacturer does things like this because they all know their customers don't know how to drive, are unlikely ever to learn, and for damned sure will never be held responsible for this in a court of law. But notice nobody here is running 8 psi, they are all about half that.

Never forget Porsche employs drivers, engineers, and… lawyers. This knowledge comes in especially handy when your car is brand new….

woodranch

So my take on the thread is 36/ 42 is the correct pressure?

chuck911

36/42 is the high side of the range. Okay if the car is really loaded down, or you crave really sharp handling and feeling every grain of sand on the road. Unless the car is heavily loaded though the tires will be hard enough to start losing grip. A lot of guys will notice the snappy handling and attribute that to better grip, at least at first. But it doesn't take much more before the loss of traction becomes really obvious- hence my skating comments. Go put 46 in there and see what I mean. Every situation is different but almost always somewhere in the 42-44 area traction suddenly falls off real fast.

Most guys only run into this at the track. But I've had it happen on the road. On a PCA Tour, nice warm day, uninterrupted twisty mountain stretch of road, suddenly the car is like on marbles. Pulled over, 44 psi. Started out, 36. Pull over, bleed, carry on. Imagine how many times I'd have to have done that if I'd started at 42.

Sorry if I'm over-explaining. The simple idea I'm trying to get across is air pressure makes the tires harder, which makes them more responsive, but can also if carried too far (i.e., beyond 42) make them lose grip. That's for the heavily loaded rear by the way. Lightly loaded front, same just sooner.

Penn4S

Turned into quite a debate as usual. A cold tire at 36 & 42 in my opinion will creep up too high once warmed up but it's really to each his own. I feel for my driving warm tires at 36 & 39 are the right limit and I that means a cold reading at 32 & 36. I'm a week at this level, I'll go a few more weeks but this feels right for me. I had the Pirellis up higher and it felt a bit stiff once warmed.

Grunty

If I set my tire pressure other than 36 44 the display keeps reading negative numbers. Is there a way to get it to stop doing that?

GSIRM3

Yep. Change settings in your TPMS from full load to partial load.

Grunty

Thanks