Joec500

I run 30/33 Cold pressure on my C2S

MKW

winter hybernation .. how

Wilkes991

very helpful guys, putting the c2 in for storage tomorrow, so will be sure to put in north of 50 psi before I put the cover on

991carreradriver

Every day at the track is different, i.e. track condition, temp, shade etc. I have tracked P-Zero's and they have a tendency to get very hot & greasy as they approach high 40's. I would recommend starting your day (assuming 68 degrees) at 27F 32R. Keep your TPMS in your view and after the first session take pressures and record. On your second session, adjust adjust the TP to target 32F 36R hot, adjusting for the increase from the first session. Keep in mind that they will cool. Note the decline prior to preparing for the next session and account for the cooling. The idea is to get as much tire on the road as possible. I adjust my pressures after every session as the day and temps progress.
Good Luck.

MKW

as you know , the factory has 4 sets of cold tire pressures for US market 991 : comfort partial full and full load weight and unlimited " autobahn run " partial and full load weight

the specs are different for every model , wheel diam and winter or summer tires and are in your specific owners manual


I have heard ...someone should confirm this..... that the " real world " chassis calibration of each model is optimized around the comfort / part load tire pressure ( the lowest of the four ) , not the max speed/ max load pressures of 36/44 which is the same across all model variant and tire sizes and is chosen mostly to minimize chance of tire blow out failure at constant 190 mph , if you know what their liabilty lawyers are worried about

MagicRat

Would be interesting to have confirmation of this. My GTS felt like it cornered way better when I reduced the pressures to that setting...

Need4S

I'm running the Comfort/Full setting of 33/40 but haven't experimented with Comfort/Partial. Would be interested in comments from those who have.

chuckbdc

33-35 cold is what I run. I got 20k miles of even wear out of the original P0s and am about halfway through (9k) miles on MSSs with great comfort and handling. They grow about 2 lbs on the highway and are very comfortable with SPASM on my C2S.

Need4S

Thanks. Good to know. I should have made clear I have a Turbo, which weighs more than a C2, so it wouldn't surprise me that slightly higher pressures are optimum for my car.

Archimedes

I run 32F/36R on my C2S P Zeros and 32 all around on my CS Goodyears.

MKW

just go into the TPM screen of your MF display ...select tire size and summer or winter tire type , and " comfort " ...then scroll up to fill info and it will tell you exactly how much air you need to add or bleed off for each tire at that moment ....it is that simple ....the fill directive automatically adjusts for the ambient garage temperature , but you still have to final set above or below that if the outside temp is much higher in summer or esp , much lower ( in winter ) than the garage temp.

checking / unchecking those two boxes requests one of the 4 sets of psi possibilities for the fill function

the computer knows which model you are driving : base, S, GTS, Turbo, RWD vs AWD , etc...each of which has different comfort psi recommendations ....pretty cool...no need to look at a cross reference chart ( there is one ) or in your manual !

chuckbdc

I really doubt that there is an arbitrary "optimum". There is a range for a reason, and what you do in that range typically is "optimum" for you.

The high end of the range Porsche suggests is for a fully laden car at autobahn speeds. I assume that means four people and over 150 mph. The low end of the range is the "comfort" setting" for more typical use. Dealers seem to fill the tires to the max when you get it serviced- likely for worse case liability protection. My guess is that if you keep it under 130 you are well safe at the more comfortable settings.

Just keep 3-4 more pounds in the rear than what you use in the front, so you get understeer rather than oversteer if you very seriously overdo it and beat the sensor based power management/ torque distribution/ wheel braking systems that are there to keep the car shiny side up.

Need4S

Thanks! I set mine to Comfort/Full today using Fill Info. What a difference in ride, and handling seem improved, too.

chuck911

It did. Of that I have no doubt. Despite slight variations across tires and conditions the following has been true of every tire and 911 made over the last- scratch that- EVER: at the low end of the range, 28-30, you get good grip, great ride and moderate responsiveness. From 32-36 great grip, good ride, better responsiveness. Around 36-40 grip starts to fall off, ride gets rough, but responsiveness is razor sharp. Much above 40 the tires are going to start skating around, what others describe as greasy. In reality they are skating, because they are hard, like a roller skate.

Anyone can test and prove all this in about half an hour, tops. Simply inflate to 44 front/ 49 rear and drive around a bit. Be careful, the car will not have as much traction as you're probably used to. Stop, bleed off 5 psi, 39/44, repeat. Ditto 34/39, 29/35. Somewhere around the last two is where you want to be. Doing this little exercise will tell you everything you need to know to fine tune the rest, including experimenting with the amount of front/rear bias.

MKW

you are welcome

here in the Bay Area, the avg outdoor daytime temps for the next 3 months ( at least for the days you would drive the 911 ) will be 54-62 degrees ...so either add an extra 1.5 lbs if filling it in your presumabably 65 degree garage or simply let car sit outside when it is 50-55 degrees , for 4 hours , and set exactly to the computer

our weather here is mild and I never bother to " bleed off air " in the summer ...whereas in the Southwest , it could be 70 in an air conditioned garage and 110 outside !

for the truly OCD or who want all the cool toys, get something like a track favorite tire temp - compensated gauge from Longacre or such ...they aren't cheap ...about $400bucks, but neither are 991s :





( btw, Porsche's fill computer sets its " zeroed " baseline at 68 degrees ambient )