Tyre pressures dropped suddenly

[Evnoob]

I’ve had my car almost a month, and in that time occasionally glanced at the tyre monitor which always showed around 3.3bar from the dealer. The app shows it in psi or kpa but don’t get me started!

today, it had been maybe 48 hours since I’d driven the car I got in the car for a long commute and almost immediately the car felt snd sounded weird, and noticeably steered to the left.

I pulled up the pressure dashboard and it showed 2.2bar. I made myself considerably late by pulling into the nearest garage and verified it wasn’t a mistake. They were only 2/3 of where they should be. So much so that it took what felt like an age to re-pump.

I thought of nefarious activity, but my security cameras show nothing and I think it unlikely that a vandal could release exactly 1bar evenly from each tyre.

I can’t think of a cause, but thought I’d post for the record.

ambient temperature was about 10c

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[tigerbalm]

FWIW, I run 2.5 bar on the front axel and 2.2 bar on the rear – which is the recommended pressures (from memory) for partial load on 20" aero wheels.

 

[Evnoob]

That’s interesting. I don’t know why they set mine to 3.3. I thought that seemed high. The manual says only 2.3

I’ll have to ask them. Hard to believe the dealer would do something by mistake

 

[Evnoob]

I still don’t know what my they’re pressures are supposed to beTLDR;

- the book says 61psi - wth?

- The door sill says 33 - could it be incorrect for the updated wheel spec?

- The dealer set them to 47

- We phoned them with the registration number of the car we bought from them - and the said 44

- an online search for the wheels and tyres I have on a base Taycan matches the 4s (I have 20” 245 front snd 285 back Pirelli summer tyres) says 39psi

I currently have them set to 33/34 (pump not too accurate) and the car claims they’re (+4) over - does the car know what wheels and tyres I have? It should, they show up in the picture on the app - but how can it know whether I’m full load or not.

I suspect that tyre deviation is delta from a previously saved measurement. So if that wasnt correct then I can’t trust the delta now.

I short, I have a premium car and I can’t be sure of the simplest most fundamental thing.

I suspect they’re supposed to be somewhere between 33 and 45 but it’s anyones guess where

 

[W1NGE]

I still don’t know what my they’re pressures are supposed to beTLDR;

- the book says 61psi - wth?

- The door sill says 33 - could it be incorrect for the updated wheel spec?

- The dealer set them to 47

- We phoned them with the registration number of the car we bought from them - and the said 44

- an online search for the wheels and tyres I have on a base Taycan matches the 4s (I have 20” 245 front snd 285 back Pirelli summer tyres) says 39psi

I currently have them set to 33/34 (pump not too accurate) and the car claims they’re (+4) over - does the car know what wheels and tyres I have? It should, they show up in the picture on the app - but how can it know whether I’m full load or not.

I suspect that tyre deviation is delta from a previously saved measurement. So if that wasnt correct then I can’t trust the delta now.

I short, I have a premium car and I can’t be sure of the simplest most fundamental thing.

I suspect they’re supposed to be somewhere between 33 and 45 but it’s anyones guess where

Rely on the door plate on the door sill - same as any other car.

 

[Evnoob]

You’d think…..but why doesn’t the car agree?

 

[Scandinavian]

I still don’t know what my they’re pressures are supposed to beTLDR;

- the book says 61psi - wth?

- The door sill says 33 - could it be incorrect for the updated wheel spec?

- The dealer set them to 47

- We phoned them with the registration number of the car we bought from them - and the said 44

- an online search for the wheels and tyres I have on a base Taycan matches the 4s (I have 20” 245 front snd 285 back Pirelli summer tyres) says 39psi

I currently have them set to 33/34 (pump not too accurate) and the car claims they’re (+4) over - does the car know what wheels and tyres I have? It should, they show up in the picture on the app - but how can it know whether I’m full load or not.

I suspect that tyre deviation is delta from a previously saved measurement. So if that wasnt correct then I can’t trust the delta now.

I short, I have a premium car and I can’t be sure of the simplest most fundamental thing.

I suspect they’re supposed to be somewhere between 33 and 45 but it’s anyones guess where

Din You ever get this sorter Daniel?

It certainly is a bit surprise to suddenly loose so much pressure in your tyres. No idea about this.

The info about 61 psi must relate to some emergency spare wheels, which we do not have. No normal tyre should need that.

Is it correct that you have 20 inch summer tyres that you want to set?

If you play around with the PCM simulator as in this link, you can set the type of tyre you have fitted , summer, winter, all season. I can also set different dimension in my car such as 20 inch or 21 inch, but that does not seem to be on the simulator.
https://your-digital-co-pilot.com/en.

It also shows how you can set the Units such as miles or km as well as pressure bar or psi if you want to change.

Remember that all recommended pressure settings are specified at 20 degrees C. If it gets colder the pressure will be less in the display etc.

Once you have selected the correct wheel size and tyre as well as the full load or normal load, you will se the pressure deviation in the display. Look at the pressure display and press the right thumb wheel and you can scroll to pressure deviation.

I would trust that deviation page and adjust my tyre pressure accordingly so that it shows 0 psi (bar). The TPMS should take into account the actual tyre temperature, which the sensor sends, but the car does not display. The System then takes temperature etc into account and displays the deviation.

My 2020 manual does not give any pressure recommendation so the dealer guru advised me to do as above. And it seems to work fine, The tyres are evenly worn over 15000 km driven.

Hope it helps.

 

[kort]

when temps drop, tire pressures will drop.
as already noted, go with the PSI on the door sticker.

 

[tomhartzell]

when temps drop, tire pressures will drop.
as already noted, go with the PSI on the door sticker.

Not a Taycan owner yet, but will share observations and lessons learned from my ICE Porsches...

Porsche's TPMS sensors measure absolute air pressure, whereas the digital gauge I use at the track measures ambient air pressure. Living in Denver, I always add three (3) lbs more pressure than the car calls for when using my gauge because the air here isn't as dense as it is at sea level. Doing this usually gets me to where the pressures needs to be as reflected in the TPMS readings from the car. Colder weather means lower tire pressures -- and they would really be low if I used the gauge and only filled the tires to the recommended pressures.

ALSO -- the Owner's Manual for my Cayenne has two pages of recommended pressures, based upon the tire size; type of tire (i.e. summer; A/S; snow; etc.) and number of occupants. There is only one recommendation on the inside of the driver's door, and that is for a fully-occupied vehicle with four people. If I used that recommendation and not what is in the Manual, I would see early / uneven tire wear.

 

[Scandinavian]

ALSO -- the Owner's Manual for my Cayenne has two pages of recommended pressures, based upon the tire size; type of tire (i.e. summer; A/S; snow; etc.) and number of occupants. There is only one recommendation on the inside of the driver's door, and that is for a fully-occupied vehicle with four people. If I used that recommendation and not what is in the Manual, I would see early / uneven tire wear.

Great if you have that in the Cayenne, but my 2020 manual has not got a single (none, nada, rien ) figure! It would have been nice to have different tables depending on tyre type and wheel sizes, but I guess they were not ready when they printed my manual.

 

[tomhartzell]

Great if you have that in the Cayenne, but my 2020 manual has not got a single (none, nada, rien ) figure! It would have been nice to have different tables depending on tyre type and wheel sizes, but I guess they were not ready when they printed my manual.

It *may* be that they're still trying to figure out the recommendations for low rolling resistance (LRR) tires vis-a-vis safety and best range, in addition to the existing tires that would fit a Taycan's various wheel sizes.

 

[Evnoob]

Not a Taycan owner yet, but will share observations and lessons learned from my ICE Porsches...

Porsche's TPMS sensors measure absolute air pressure, whereas the digital gauge I use at the track measures ambient air pressure. Living in Denver, I always add three (3) lbs more pressure than the car calls for when using my gauge because the air here isn't as dense as it is at sea level. Doing this usually gets me to where the pressures needs to be as reflected in the TPMS readings from the car. Colder weather means lower tire pressures -- and they would really be low if I used the gauge and only filled the tires to the recommended pressures.

ALSO -- the Owner's Manual for my Cayenne has two pages of recommended pressures, based upon the tire size; type of tire (i.e. summer; A/S; snow; etc.) and number of occupants. There is only one recommendation on the inside of the driver's door, and that is for a fully-occupied vehicle with four people. If I used that recommendation and not what is in the Manual, I would see early / uneven tire wear.

So you’re saying you DONT use the door pillar plate recommendations?

my issue now, having used those, is that the car still thinks they’re wrong.

 

[W1NGE]

So you’re saying you DONT use the door pillar plate recommendations?

my issue now, having used those, is that the car still thinks they’re wrong.

Have you checked what wheels / tyres are set in the PCM (Settings, Vehicle Settings, Car, Tyre Pressure Monitoring) so that the TPMS communicates correctly?

I always go with the door sticker and follow the typical load there - Porsche Good To Know App (if not already reviewed) should be an authoritative reference point too.

 

[tomhartzell]

So you’re saying you DONT use the door pillar plate recommendations?

my issue now, having used those, is that the car still thinks they’re wrong.

If the only guidance from Porsche is on the door pillar, I would absolutely use what is provided on the door pillar. (Assuming what Scandinavian has indicated about not having any guidance in the Manual is true for all Taycans.)

The pressure in your tires will change constantly, based upon the temp outside; your altitude; the amount of time you have been driving; etc. Tire pressure should be set when they're cold keeping the 20C/68F guidance Scandinavian mentions. If it's 27C/80F when you check them, add a little pressure to ensure tire pressures come back down to the desired pressure when the temperature is lower. Conversely, if it's 15C/55F when you check the tires reduce the pressure you add. The tire pressures will increase as the temps increase. My tire pressures are only on the "recommended" when I first start driving the car. (And unless there is a considerable dropoff in pressure in one of them, I don't worry about the pressures. They are always lower than recommended when driving in the cold and snow.) The value of TPMS is letting you know when a tire is starting to lose a lot of pressure, and for letting you know what the pressures are when you first start the car -- given the influence of the temp outside and your altitude.

Let me know if this didn't make sense. Thanks!

 

[W1NGE]

If the only guidance from Porsche is on the door pillar, I would absolutely use what is provided on the door pillar. (Assuming what Scandinavian has indicated about not having any guidance in the Manual is true for all Taycans.)

The pressure in your tires will change constantly, based upon the temp outside; your altitude; the amount of time you have been driving; etc. Tire pressure should be set when they're cold keeping the 20C/68F guidance Scandinavian mentions. If it's 27C/80F when you check them, add a little pressure to ensure tire pressures come back down to the desired pressure when the temperature is lower. Conversely, if it's 15C/55F when you check the tires reduce the pressure you add. The tire pressures will increase as the temps increase. My tire pressures are only on the "recommended" when I first start driving the car. (And unless there is a considerable dropoff in pressure in one of them, I don't worry about the pressures. They are always lower than recommended when driving in the cold and snow.) The value of TPMS is letting you know when a tire is starting to lose a lot of pressure, and for letting you know what the pressures are when you first start the car -- given the influence of the temp outside and your altitude.

Let me know if this didn't make sense. Thanks!

It's not the only guidance - Porsche Good To Know App and the Owners Manual (hard copy and the PCM electronic one ).

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