My car told me to add air today!

[DRJMK]

I haven't seen any posts like this, but my 997.2 C2S gave me a warning to add air, 5lbs in the front and 7 in the rear. Wow, that's amazing!

[Edgy01]

When it tells you that you need to take a closer look. Those amounts of air just don't disappear overnight unless you have some sort of issue. The most I ever notice over time is perhaps 2 lbs. But when 7 is missing in a rear--you have a slow leak which tells me "nail."

[jinto]

could be temperature drop, tire pressure changed? but best to check out with tire shop, one time I had 3 nails in my rear left tire.

[DRJMK]

it could be the cold...but I am taking it to the tire shop in the morning just for a check. Running pressures are 30 on the front and 37 in the rear according to the tpms.

[ADias]

Originally Posted by jinto

could be temperature drop, tire pressure changed? ...

I bet that's that.

[Coochas]

Originally Posted by DRJMK

it could be the cold...but I am taking it to the tire shop in the morning just for a check. Running pressures are 30 on the front and 37 in the rear according to the tpms.

Crank the front up to 32-33 cold and you'll be OK.
I like to run my fronts at 30 but now that we've had a few days in the 30s-40s, the cold pressure drops to 27 which sometimes triggers the "add air" thing.

[PogueMoHone]

Originally Posted by Coochas

Crank the front up to 32-33 cold and you'll be OK.
I like to run my fronts at 30 but now that we've had a few days in the 30s-40s, the cold pressure drops to 27 which sometimes triggers the "add air" thing.

Dave,

I don't know the Turbo pressures off hand but on a 997 S that is too low (street or track). Ideal is F (32-34)--R(38-40) @68F. These pressures hold no matter the application, street or track; and the 8lb spread is enough to play with over/understeer for your preference(s); and if that is really not enough you could stretch another 2 lbs in the rear (but not the front).

You can run track tires at lower pressures, but theoretically and practically you go up in pressure on street tires at the track, and this is recommended by most experts and set up specialists.

However, the fully loaded pressures 37/44 cause too much understeer, so those pressures are outside the envelope, except for fully loaded street driving.

I have long been amazed at the amount of fiddling people do with tires (at the track and autocross... maybe it is a "good luck charm"). When you ask the "set up" guys why people do it on street tires..you generally just get a big smile and a shrug.

[Coochas]

Originally Posted by PogueMoHone

Dave,

I don't know the Turbo pressures off hand but on a 997 S that is too low (street or track). Ideal is F (32-34)--R(38-40) @68F. These pressures hold no matter the application, street or track; and the 8lb spread is enough to play with over/understeer for your preference(s); and if that is really not enough you could stretch another 2 lbs in the rear (but not the front).

You can run track tires at lower pressures, but theoretically and practically you go up in pressure on street tires at the track, and this is recommended by most experts and set up specialists.

However, the fully loaded pressures 37/44 cause too much understeer, so those pressures are outside the envelope, except for fully loaded street driving.

I have long been amazed at the amount of fiddling people do with tires (at the track and autocross... maybe it is a "good luck charm"). When you ask the "set up" guys why people do it on street tires..you generally just get a big smile and a shrug.

I found that even on my street tires I ran 27/31 cold which went up to the high 30s hot on track (on the 997TT).
I prefer my tires with lower pressure on the street and like the softer ride that they afford. I think this helps a lot around here with all the bumps and potholes. Performance wise on the street they're just not a factor as I'm never near the limit! They also go up about 4 psi just during my short commutes. I also ran my pressures on the lower side with my C4S. Never had a problem with any summer tire in 5 years....I think the tires are happier like this!

[ADias]

Originally Posted by PogueMoHone

Dave,

I don't know the Turbo pressures off hand but on a 997 S that is too low (street or track). Ideal is F (32-34)--R(38-40) @68F. These pressures hold no matter the application, street or track; and the 8lb spread is enough to play with over/understeer for your preference(s); and if that is really not enough you could stretch another 2 lbs in the rear (but not the front).....

I would just add that the setting temp is whatever the cold temp for the day is - morning car start temp. Out West it may be a comfortable 68F and back East it may be 40F or lower. The setting 'cold' pressure (34/40) is the same, regardless of the ambient temp.

On a Summer day a tire needs less air than on a Winter day to reach a given pressure (PV=nRT), therefore a tire set on a Summer day (morning temp 68F) will be somewhat deflated on a cooler Fall 40F morning. I think this is what the OP observed.

[ADias]

Originally Posted by Coochas

I found that even on my street tires I ran 27/31 cold which went up to the high 30s hot on track (on the 997TT).
I prefer my tires with lower pressure on the street and like the softer ride that they afford. I think this helps a lot around here with all the bumps and potholes. Performance wise on the street they're just not a factor as I'm never near the limit! They also go up about 4 psi just during my short commutes. I also ran my pressures on the lower side with my C4S. Never had a problem with any summer tire in 5 years....I think the tires are happier like this!

You should run at the recommended pressures, not lower. Unless you drive slowly... with lower pressure you are prone to blowouts and (counter-intuitive) wearing the tire centers. This has to do with the characteristics of these tires - stiff sidewalls and low profiles..

[OldGuy]

Dont get too excited about this. The dang things can be a pain in the arse. If say for conversation the
pressure goes below 30lbs to 29, it goes off because the other tire is 30 lbs. They are only 1 lb off but you get that annoying lite and it stays on till you fix it even if the temp goes up and the pressure goes up.
You have to put air up to like 35 or 40 to get the light off and now you have 40 in the right front and 30 in the left front. ALOT Of guys in the GT3 community went to Porsche and had the dealer disable it.

[DRJMK]

well, i really think it is the cold. it's been about 40 here in the morning and 70 in the afternoon. but, it gave me the warning yesterday afternoon as well. It was even pressure on all 4 corners, 5 each in the front and 7 in each rear. I will have them put in the recommend running pressures and see what happens. If it does it every morning when it's cold, that would be annoying!

[GSIRM3]

Originally Posted by DRJMK

well, i really think it is the cold. it's been about 40 here in the morning and 70 in the afternoon. but, it gave me the warning yesterday afternoon as well. It was even pressure on all 4 corners, 5 each in the front and 7 in each rear. I will have them put in the recommend running pressures and see what happens. If it does it every morning when it's cold, that would be annoying!

The TPMS won't alarm each morning if you set the pressures correctly to the recommended "cold" pressures. If you set them when the tires are hot, and in the warmer afternoon, then the monitor might go off in the mornings because of the reduced pressure when the tires are cold and ambient temp lower.

[cab&coupe]

Paul's got it right... anyone taking their 997 GT3 to the track knows about the dreaded TPMS. IIRC.. the variance is 6 or 7 pounds?

Lesile... would you rather have your car or a significant other remind you?

[ADias]

Originally Posted by DRJMK

well, i really think it is the cold. it's been about 40 here in the morning and 70 in the afternoon. but, it gave me the warning yesterday afternoon as well. It was even pressure on all 4 corners, 5 each in the front and 7 in each rear. I will have them put in the recommend running pressures and see what happens. If it does it every morning when it's cold, that would be annoying!

Make sure they set the pressures right - low load 34/40. Dealers tend to set it at full load 37/44.

If you have the dealer do that, you must leave the car there to cool down before they fill the tires. I suggest you do it yourself in the comfort of your garage with an inexpensive compressor.