Tyre Pressures and warnings

[plisken]

Not normally something that really bothers me or would bring me to a forum, unless puncture related of course as I hate punctures, but that's another story.

So, this morning I get the alert and sure enough 3 of the 4 are showing orange and are at 37/38 but one of them remained white, also showing 38, hmm, interesting I thought, maybe it was rounding down for the display or something and simply drove on. It was 5 degC outside.

I get to my destination, alert still on, this time though, all are showing 42/43 but again, the same 3 out of the 4 are showing orange and one in white. I know 42 is ok as I drove for months with 42, so what could be going on here. Kind of not working as expected. Is there anything Tesla actually got right?

 

[exlatccatsa]

This happens to me in spring and autumn when outside air temperatures change significantly this changes the density of the air inside the tyres, hence the warnings.

 

[TechnoWatch]

This happens to me in spring and autumn when outside air temperatures change significantly this changes the density of the air inside the tyres, hence the warnings.

It is possible that the car is calculating the cold pressure of the tyres (which is normally expected to be 42psi) by using current tyre pressure and temperature and extrapolating the cold pressure based on outside temperature.

It would be interesting to know if the warning goes away when the outside temperature rises significantly during the day?

 

[plisken]

It's strange that one is showing as white as in no warning and in the case of the last time I looked this was actually 1degC lower than the other three, which remained on orange.

Of course I completely understand the pressure dropping in colder weather but this is a head scratcher...

 

[exlatccatsa]

Is it possible the sun was warming one tyre before you set off?

 

[GeorgeSymonds]

I believe they use a range band where it alarms when it falls below the lower number but doesn’t clear until it exceeds the higher number, presumably to stop it flicking in and out of alarm all the time. It can look weird but is perfectly normal operation, it just means 3 tyres at some point dropped below the alarm level but the 4th didn’t, and they are all higher now but not to a level to clear the alar, either way, you need to add air and they’ll clear

 

[MrBadger]

So, this morning I get the alert and sure enough 3 of the 4 are showing orange and are at 37/38 but one of them remained white, also showing 38, hmm, interesting I thought, maybe it was rounding down for the display or something and simply drove on. It was 5 degC outside.

The Model 3 TMPS is/was set at 42psi and the warning is triggered at -10% (and possibly also at +10%), so -4.2psi. This allows the warning to be triggered at 37.8psi which, as far as the car display goes, is 38psi. So one of your 38psi's are below that threshold, the other still above. But both will be displaying as 38psi. So that would explain the first one.

I cannot remember exactly but I do not believe that the sensor until start of next drive (unless reset?) - which would make sense as the pressure has dropped below the alert limit and tyres warming/gaining pressure during a journey is not a fix for a low pressure, potentially compromised tyre.

This time of year we will start seeing tyre pressures potentially start to drop significantly overnight (not yet at that point in the south) especially if tyres were not set to 42psi when cold or the tyre was inflated/deflated with one side sat in the sun, so pressures will potentially start edging towards the 37.8psi.

Another thing for recently new owners, is don't expect the tyres to be set properly for collection. These cars are not PDI's and last time your tyres will have been set for pressure would have been Shanghai...

 

[init6]

Is it possible the sun was warming one tyre before you set off?

I've had that when the temp drops overnight. I had one tyre looking ok, but other 3 low. Then realised that the one 'good' tyre was sitting in the sun while the others were in shade.

 

[Toblerone]

don't expect the tyres to be set properly for collection.

This may have changed recently, as Q3 MY collections are reporting the on-screen display showing 42psi.

Perhaps this is due to all the noise about MY ride quality so they are correcting it after transport?

Either way, I’ll be checking and adjusting once home and cold.

 

[kelvin 660]

This topic must have been a coincidence, as I pumped up all 4 tyres this morning (added ~4 psi) as I had noticed the pressure were going down (TeslaFi report) and I didn't want to get any warnings as I've got a long drive later today!

 

[chot2022]

This topic must have been a coincidence, as I pumped up all 4 tyres this morning (added ~4 psi) as I had noticed the pressure were going down (TeslaFi report) and I didn't want to get any warnings as I've got a long drive later today!

I noticed yesterday that my tires were showing 41 psi/40 psi. Wondering how it went down so much. Most of summer it was 43/42 psi.

 

[init6]

I noticed yesterday that my tires were showing 41 psi/40 psi. Wondering how it went down so much. Most of summer it was 43/42 psi.

What were the temperatures in summer compared to now?
Also your tyres will gradually lose air over time.

 

[MrBadger]

This may have changed recently, as Q3 MY collections are reporting the on-screen display showing 42psi.

Perhaps this is due to all the noise about MY ride quality so they are correcting it after transport?

Either way, I’ll be checking and adjusting once home and cold.

I meant tyre pressures rather than TPMS settings - based up previous experience, its very likely that the last time that the tyres of a recent vehicle had any air put in them was at Shanghai. Certainly, as far as the Freemont cars were concerned that were delivered at around this time of year, it wasn't long before many started giving pressure warnings as unless topped up by the owner, temperatures in Fremont were much higher than early morning autumn mornings so not much room for pressures to drop below the warning trigger. Happened to us the first really chilly morning after taking delivery.

 

[Lockey]

The Model 3 TMPS is/was set at 42psi and the warning is triggered at -10% (and possibly also at +10%), so -4.2psi. This allows the warning to be triggered at 37.8psi which, as far as the car display goes, is 38psi. So one of your 38psi's are below that threshold, the other still above. But both will be displaying as 38psi. So that would explain the first one.

I cannot remember exactly but I do not believe that the sensor until start of next drive (unless reset?) - which would make sense as the pressure has dropped below the alert limit and tyres warming/gaining pressure during a journey is not a fix for a low pressure, potentially compromised tyre.

This time of year we will start seeing tyre pressures potentially start to drop significantly overnight (not yet at that point in the south) especially if tyres were not set to 42psi when cold or the tyre was inflated/deflated with one side sat in the sun, so pressures will potentially start edging towards the 37.8psi.

Another thing for recently new owners, is don't expect the tyres to be set properly for collection. These cars are not PDI's and last time your tyres will have been set for pressure would have been Shanghai...

I've had tyre pressure warning pop up (and clear after a few mins driving) the last couple of days and I'm in South West England so it's even cold enough in the South!

 

[kelvin 660]

I've attached a graph of temperature verse pressure, since March till now... If anyone is interested.

 

[Masklin]

Mildly interesting… my Model 3 Performance the label in the passenger door says pressures should be 42psi front and rear, whilst after a recent software update (forget which one) the service page with tyre pressures on the screen now says they should be 43psi front and 42psi rear.

 

[MrBadger]

Another point of reference, first frost of the season this morning, 5C. Tyre pressures just over 39psi, 'normal' daytime temperatures, 42psi. So a drop of around 3psi overnight.

 

[Adopado]

You also can't just rely on the screen info. Inevitably that is going to show pressures when the car has been driving along so will be a few pounds higher than the "cold" (read "ambient") setting. (When stationary the car read out now snap-shots a reading from your last drive which is likely to be relatively high.) The read out should be pretty close if you look at it very soon after you have departed and the last readings have been refreshed but after that they're going to climb. It seems that there's no good replacement for getting down on your knees and testing with a reliable gauge unfortunately.

 

[DrJFoster]

You also can't just rely on the screen info. Inevitably that is going to show pressures when the car has been driving along so will be a few pounds higher than the "cold" (read "ambient") setting. (When stationary the car read out now snap-shots a reading from your last drive which is likely to be relatively high.) The read out should be pretty close if you look at it very soon after you have departed and the last readings have been refreshed but after that they're going to climb. It seems that there's no good replacement for getting down on your knees and testing with a reliable gauge unfortunately.

Agreed it's a potential issue - I've read BMW have temperature and pressure sensors in the tyre and adjust the target temperature based on actual tyre temp relative to ambient temp so while the pressure may be higher because of use, they tell you the tyre should be inflated to a higher pressure when the tyre is warm.

I use the poor man's version of that, I'll pop the tyre pressures up on the screen when I start driving and as soon as they appear make a mental note of how far out they are. If they're reading 2psi low when I first start driving, I'll over inflate them by 2psi when they're warm, whilst supercharging is a good opportunity. I doubt it's 100% accurate but it's a good enough approximation for me.

 

[MrBadger]

You also can't just rely on the screen info. Inevitably that is going to show pressures when the car has been driving along so will be a few pounds higher than the "cold" (read "ambient") setting.

Or get the data from the API such as via TeslaFi. That doesn't report until it gets live data.