tekaefixe

Hi dear friends of the Forum : )

Since im new to the Porsche World could you please advise me to which is the ideal tire (summer/winter) pressure for Turbo S 20" ??

Basically the car gives me 3 options after you chose winter or summer tire :

1 - Comfort mode (limited to 270km/h) must tick the box
2 - Full Pressure must tick the box
3 - No box ticked (this means no TPM measurement)

Now im in the full preassure mode but the car is very hard and jumpy. My questions are, when should one use the Full preassure mode? Just to achieve maximum speed? On the track?

If I select none of the boxes can I still achieve max speed? When should this setting be used?

Sorry for so many questions but im really new to this eheh ; )

Have a great weekend everyone and thanks a lot for the help!+

GrandLaker

I run 32/36 but even when mine was at full PSI from factory it was never jumpy.

worf928

Jumpy is in the eye of the beholder ... or... err ... seat of the pants.

There is a noticeable difference in feel between comfort and standard pressures.

I run the comfort pressures.

The standard pressure is to ensure that you can sustain maximum speed without a blowout.

Oh... on a road course you would run lower-than-comfort pressure depending upon expected sustained speed.

porsche42

I run 34/43 I think that is the comfort pressure in the manual. Works fine for me a tad stiff, but it is a sports car. Certainly not jumpy.

worf928

Part load comfort cold pressure for 20"s, for the 991 TT and TTS is:
31 PSI front
36 PSI rear

Full load is:
33 PSI front
40 PSI rear

Dry weight is ~3516 lbs. Maximum weight is ~4387 lbs.

That gives a ~870 lbs loading range.

For me, anything more than two adults and a little bit of luggage means that the tire pressure may need to be raised if there is an expectation of extended high-speed (which is, of course, not the expectation in the US and thus I always run comfort pressure on the street.)

Given that the maximum speed for comfort settings is 165 mph / 270 kph, even on the Autobahn two adults and a little bit of luggage is still fine for comfort pressures. It's pretty hard to sustain >165/270 for more than a few 10s of seconds under nominal autobahn conditions.

On the other hand, if it's 2 AM east of The Rhine and you are attempting to reach the top speed you must go to the standard pressure settings. The standard settings are "Lawyer" settings to ensure that the top speed can be sustained without bursting the tires.

PV=nRT (mostly) and thus...

It's all about dissipating the heat from the flexing of the sidewalls and tread. The faster you go the less time any non-flexing part of the tire has to dissipate heat. Raising pressure stiffens the sidewalls, reduces the size of the contact patch and therefore results in less heat generation (because there's less flex and slightly less area that flexes) and slightly more time for any non-flexing part of the tire to dissipate heat.

There is an average tire temperature at which the contact patch is maximized. This is the temperature one seeks-out when tracking a car so-as to maximize cornering speeds. This is a different context than sustained straight-line-autobahn running as average track speeds will be far less (even on the Nordschleife) and thus considerations of what pressures to use are different and more complex (see the Racing Forum(s).)

tekaefixe

So basically when you say standard pressure setting its not Full Load, standard pressure setting is what you even when both boxes (full load and comfort) are unchecked right?

rcg412

Comfort pressures, 31/36 for me

In winters I ran this as well, although winter comfort tire pressure is higher at 33/39 I believe

Track tires I aim for hot, 35/36. (Pilot sport cup 2)

NVRANUF

There's cold pressure and hot pressure.
Can't use both, so which one do folks typically use?

Plus different brands of tire perform "best" at different optimum pressures.
It seems there's no cookie cutter answer....

worf928

Yes and yes.

worf928

Cold pressure for the street. Hot pressure for the track.

Overdraft

Wait a minute! What about what is on the door label....mine says 37F 47R on my Pirelli P Zero which is lots more than you all appear to be running...?

worf928

That's standard tire pressure for full load. Or, in other words: full lawyer pressure for sustaining top speed.

Drop it down to comfort pressure and you'll notice a far better ride, more grip, and your tires will wear more evenly.

Randyc151

I run at comfort pressure mode year round, and measure at 72 degrees in the shade. Typically, that's 32f/34r. It generally gets to 34f/36r after casual driving.

For track, I start at 26 to 28 front and rear, depending on the outside temps, and never let it go above 35.