Tire Pressure Mismatch?

[brianbcc]

New 2023 M3 SR here.

Just a few weeks old and loving it.
This forum is excellent for info, so many thanks!

Not sure if this is something to stress about but I know that the recommended tire pressure should be 42psi.
I checked manually with two different gauges and confirm the 42psi.
However, the onscreen and app tells me the psi is 45.
So it's a mismatch.
Should I be worried?
Because i know the system won't warn me unless it's down to 39, but if the system is misreading, then it would actually be less and the warning would be late?

And I do check when the car hasn't been used for at least a day.

I'm in the Bay Area, so temps are normal here.

Thanks!

 

[holmgang]

you need to calibrate it. its in the manual (which is accessible in the car computer). set the cold pressure to the reference pressure. activate the calibration. then it will learn from there

 

[EVRider-FL]

The car doesn’t update tire pressures until you’ve been driving for several minutes, during which time the tires can warm up causing the pressure to increase. I would drive for 10 minutes and then check the pressure in both the car and with the gauge to compare them.

 

[AdamVIP]

I think an update added the ability to spot check tire pressure without having to drive it to fire them up.

 

[MLXXXp]

I think an update added the ability to spot check tire pressure without having to drive it to fire them up.

This only gives the previous tire pressures and the time they were taken. The sensors have to rotate to get them to activate. There's no way to turn them on remotely.

 

[Randy-12]

you need to calibrate it. its in the manual (which is accessible in the car computer). set the cold pressure to the reference pressure. activate the calibration. then it will learn from there

Where do you see this? I see nothing about the user having to do anything but drive.

Model 3 Owner's Manual | Tesla

Learn about tire specifications, tire pressures and seasonal tires.

www.tesla.com

 

[thimel]

I’d also suggest trying a few pressure gauges. Not all are accurate to a few PSI.

 

[afadeev]

Not sure if this is something to stress about but I know that the recommended tire pressure should be 42psi.
I checked manually with two different gauges and confirm the 42psi.
However, the onscreen and app tells me the psi is 45.
So it's a mismatch.

What gauges did you use?
Cheap pencil types, or something that cost you > $50?
If the former - your readings were wildly inaccurate. If the latter, and the quality pressure gauge was recently calibrated (and not dropped), then you need to (a). reset TPMS sensors, and/or (b). manually reset your TPMS values.

Should I be worried?

Would worrying help?

Because i know the system won't warn me unless it's down to 39, but if the system is misreading, then it would actually be less and the warning would be late?

No such thing as "too late".
Driving on 35psi will only make the ride more enjoyable on third-world Bay area roads.

I'm in the Bay Area, so temps are normal here.

There is not much "normal" about the Bay Area, but do enjoy your new ride!

HTH,
a

 

[brianbcc]

Appreciate the advice and thanks all!

 

[Randy-12]

... then you need to (a). reset TPMS sensors, and/or (b). manually reset your TPMS values.
View attachment 934687

What is the source for this?
I can't find it in the manual or the do it yourself guide

 

[ColoradoMike]

What is the source for this?
I can't find it in the manual or the do it yourself guide

Yeah I could not find that either in the Manual. Would love to know the source as well....I use my track tire gauge that is properly calibrated and I show 1 lb less on the TPMS sensors. Not certain why but it that's the way the car has been. I check our tires every week or so on all our vehicles due to CAR OCD...LOL!

 

[ay221]

I have a 60ish dollar air pressure gauge. I set it to 42 psi but the tpms sensors when I first start driving read it as 40 psi. I think the gauge would be more accurate, but not positive. I know there are like $300 gauges and beyond, but I don't think I need really need to do that.

 

[fholbert]

The car doesn’t update tire pressures until you’ve been driving for several minutes, during which time the tires can warm up causing the pressure to increase. I would drive for 10 minutes and then check the pressure in both the car and with the gauge to compare them.

With other cars I’ve owned that’s true.

I was really surprised yesterday. My MY said my tire pressure was 37 to 39psi after driving 6 miles to the airport. I rotated my tires in the shade of my hangar, while all the tires were off I added air to all 4 tires bringing the pressure up to 42psi. I finished the rotation and walked to my friends hangar for lunch.

An hour later I returned and backed out of the hangar, maybe 50‘. The increased tire pressure was already being displayed and it had been recorded while I was eating.

The new location of the tires wasn’t known yet, but that changed in less that a mile of low speed driving.

 

[zroger73]

The sensors have to rotate to get them to activate. There's no way to turn them on remotely.

On my Hondas and Mazdas, there is an "initiator" (low frequency antenna) near each wheel. Each time the vehicle is powered on, a signal is broadcast from each antenna - one at a time - in sequence. The signal is only strong enough to reach the nearest TPMS sensor. The vehicle initiates a request from the first sensor which wakes it up and causes it to transmit its ID, pressure, temperature, and battery voltage over a higher frequency which is received by a different antenna. By initiating each TPMS sensor individually, this is how the vehicle knows where each sensor is located without telling it. The wheels do not have to rotate to send a signal. When they are rotating, they transmit once every 60 seconds; otherwise, they transmit when the pressure drops quickly or if a signal is received from the initiator.

Tesla uses individual antennae near each wheel and automatically recognizes the new wheel positions at each rotation, so it is logical to conclude that Tesla's TPMS operates no differently than other brands with this design of TPMS.

 

[afadeev]

I was really surprised yesterday. My MY said my tire pressure was 37 to 39psi after driving 6 miles to the airport. I rotated my tires in the shade of my hangar, while all the tires were off I added air to all 4 tires bringing the pressure up to 42psi.

Few observations:

1. Tesla (and most other OEM's) TPMS sensors are not very precise. From the factory, brand new TPMS sensors are expected to give +/- 3% error of actual vs. displayed pressure.
2. Tire air pressure changes significantly with the environment to which it is exposed. Leave one side facing the sun, and the temps/pressures on that side will go up. Drive through a puddle, and the tires that got exposed to water will have their temps/pressure go down vs. those that stayed dry.
3. The only way to measure you tire pressure accurately is with a quality, recently calibrated pressure gauge. Not a cheap pencil thing, but a quality gauge that costs more than $30.

Anyone aware of a good quality, accurate tire pressure gauge which is reasonably priced?

I had a Meisner Accu-gage for over 60 years , still accurate but the release button no longer held pressure when released. I contacted the company and they could not provide parts to seal mine so they sent me a new one -free.

community.cartalk.com

An hour later I returned and backed out of the hangar, maybe 50‘. The increased tire pressure was already being displayed and it had been recorded while I was eating.
The new location of the tires wasn’t known yet, but that changed in less that a mile of low speed driving.

Pressure are actively updated only during driving.
I haven't timed the exact distance it takes my TPMS reading to update, but it's usually more than a few minutes and 1/2 mile. By the time I drop kids off at school, they are usually accurate (5 mins, 1.3 miles). Until then, it's a crap shoot.

HTH,
a