i386_64

Today, I was driving back from holiday in Greece. It was a warm and humid day, showing 42.5C (108.5F) on the dashboard. Before I started driving, knowing that I'm going to do highway speeds under the sun, I prepared the tyre pressures with 45psi and 48psi. 22" summer tyres, full load setting, non-comfort pressures.

Jumped to the road, after going for 30 kms, it gave me a low pressure warning. After reaching 160 km/h (100 mph), it started doing a red warning, suggesting me to put +5psi on the fronts and +7psi on the rears. At the time, rears were already 49psi, so it was basically telling me to make it 56psi! The tyres are Michelin Pilot Sport 4S and the reading on the sidewall tells me to not exceed 50psi.

Called Porsche and they suggested me to do 43psi and 45psi instead, having told me that PCM might be outdated in terms of specifications and I should rely on their information. But it wasn't a calm driving, giving me red warning all the time like the tyres are burst.

Has anyone encountered anything like that, especially in warmer climates, should I really ignore the warning and continue driving?

Having read @Schnave s extensive documentation on RL, we're not supposed to alter the pressures as we're driving along, but this is just nonsense. I'm using a calibrated pressure gauge, and I think a couple of psis shouldn't make that much difference.

retom

After changing the pressure, did you update it in the TPM system?
If so, the yellow and red warnings may indicate a fault in this system or too high tire temperatures.
Unfortunately, Porsche, unlike most other manufacturers, does not display tire temperatures. This is strange because the TPM is the same as in the Audi (which shows pressure and temperature) and the wheel sensors send such information to the system.

ThomasWShea

i recently talked offline w @retom on this. The pressures are cold pressures. So if they are correct when u start driving, they may rise, but this is accounted for in the recommended cold pressure value - filled at 68F or whatever the cold temp is. As the tires raise in pressure they become stiffer and move less and this keeps them from raising even more. I use the sticker values which line up in the pcm w the partial load all-season values. my car came w all seasons. Now, even with it hot outside, when i pull out of my garage the initial reading is the correct pressure even if it is 90F outside. then after a few mins the pressures start rising due to the hot roadway etc.

canuckporsche

I had similar discussions with my dealer who wanted to put 48 in all tires yet the door says 44 full load. We agreed on 46 as a compromise selection. Our weather is all over the map so the tires are showing between 44 and 48 on any given day, I do not get messages to put more air in. I have also observed the tire pressures reported using the app tend to be slightly higher than those showing in the instrument panel. I do find at 48 the ride is getting rough in sport mode vs 44.

jadatis

Mind that problems with tmps are of secundary importance, but can give confusion.
important is to fill cold the right pressure.
cold is when temp in tire is same as outside tire, that simple.

First, tires have teststandards that they must stand 2 to 3 times the reference-pressure, is of your most likely XL tire 2.9 bar/42 psi.
so warm it may rise to 5.8 bar / 84 psi.
​​​​​So if filled at freesing point with 1.4 x referencepressure, and incidentially temp in tire rises to 100 degr C , boiling point of water, pressure rises to about 2x referencepressure, so yust within the teststandards.

Porche and BMW give on tmps screen the actuall gaugepressure in tire, send by the sensor, but per axle recomended pressure for the situation setting, calculated from an index temperature of 20 degr C/ 68vdegr F, to the temperature of gascompound in tire, also send by the sensor.

So if you filled at 42 degr C your pressures, you should also calculate it from 20 degr C to 42 degr C. , and it gives even higher pressure to fill
you can use list I made for that, acurate enaugh for the goal, and can calculate by head with it .

2 lists .
1 for index temp of 20 degr C and per 0.1 bar cold pressure given, gives degr C change per 0,1 bar .
2. For index temp 70 degr F ( 21 degr C , for easy calculating) and gives degr F change per 1 psi.
both rounded to 0.5 degr.

20 degr C / degr C / 0.1 bar.

1,5 bar/ 11,5 C/0,1bar

1,6 bar/ 11 C/0,1bar

1,7 bar/ 11 C/0,1bar

1,8 bar/ 10,5 C/0,1bar

1,9 bar/ 10 C/0,1bar

2,0 bar/ 9,5 C/0,1bar

2,1 bar/ 9,5 C/0,1bar

2,2 bar/ 9 C/0,1bar

2,3 bar/ 9 C/0,1bar

2,4 bar/ 8,5 C/0,1bar

2,5 bar/ 8,5 C/0,1bar

2,6 bar/ 8 C/0,1bar

2,7 bar/ 8 C/0,1bar

2,8 bar/ 7,5 C/0,1bar

3,0 bar/ 7,5 C/0,1bar

3,1 bar/ 7 C/0,1bar

3,3 bar/ 7 C/0,1bar

3,4 bar/ 6,5 C/0,1bar

3,6 bar/ 6,5 C/0,1bar

3,7 bar/ 6 C/0,1bar

4,0 bar/ 6 C/0,1bar

4,1 bar/ 5,5 C/0,1bar

4,5 bar/ 5,5 C/0,1bar

4,6 bar/ 5 C/0,1bar

5,1 bar/ 5 C/0,1bar

5,2 bar/ 4,5 C/0,1bar

5,8 bar/ 4,5 C/0,1bar

5,9 bar/ 4 C/0,1bar

6,8 bar/ 4 C/0,1bar

6,9 bar/ 3,5 C/0,1bar

8,0 bar/ 3,5 C/0,1bar

8,1 bar/ 3 C/0,1bar

9,6 bar/ 3 C/0,1bar

9,7 bar/ 2,5 C/0,1bar

12,0 bar/ 2,5 C/0,1bar



70degrF./degrF/psi



20 psi/ 15,5F/psi

21 psi/ 15F/psi

22 psi/ 14,5F/psi

23 psi/ 14 F/psi

24 psi/ 13,5F/psi

25 psi/ 13,5F/psi

26 psi/ 13 F/psi

27 psi/ 12,5 F/psi

28 psi/ 12,5 F/psi

29 psi/ 12 F/psi

30 psi/ 12 F/psi

3 1. psi/ 11,5 F/psi

32 psi/ 11,5 F/psi

33 psi/ 11 F/psi

34 psi/ 11 F/psi

35 psi/ 10,5 F/psi

36 psi/ 10,5 F/psi

37 psi/ 10 F/psi

39 psi/ 10 F/ps

40 psi/ 9,5 F/psi

42 psi/ 9,5 F/psi

43 psi/ 9 F/psi

45 psi/ 9 F/psi

46 psi/ 8,5 F/psi

49 psi/ 8,5 F/psi

50 psi/ 8 F/psi

53 psi/ 8 F/psi

54 psi/ 7,5 F/psi

58 psi/ 7,5 F/psi

59 psi/ 7 F/psi

63 psi/ 7 F/psi

64 psi/ 6,5 F/psi

70 psi/ 6,5 F/psi

71 psi/ 6 F/psi

77 psi/ 6 F/psi

78 psi/ 5,5 F/psi

86 psi/ 5,5 F/psi

87 psi/ 5 F/psi

96 psi/ 5 F/psi

97 psi/ 4,5 F/psi

109 psi/ 4,5 F/psi

110 psi/ 4 F/psi
126 psi/ 4 F/p

Orca911

The system has a hard time with fluctuations.
Read some threads on GT3 forum where track temps can go up and down.
The TPMS monitoring is something you have to pretty much ignore.

swoop1156

We swapped our 22 inch 911 Design Wheels for some 21 inch Turbo wheels, changed settings within the PCM, and it's always been buggy. We just had service at the dealer and they, too, said just make sure that the pressure is what it's supposed to be and live with the warning lights. Not really what I want to do...