Tyre pressure monitor accuracy

Tyre pressure monitor accuracy

I have an AWD with 19 inch wheels. The sticker by the door says the tyres should be inFlated to 42 psi (cold).

I've tried several inflators - I set them to 42 psi and begin inflatjng. However , when I check the touch screen within the car it only shows me 40 psi. Has anyone else experienced this ? Is the cars sensors more accurate ( meaning I need to set it to about 44 psi when inflating?) Or are the sensors off?

coleAK | December 6, 2018

You need to drive a short distance (should be <1 mile) for the sensors to pick up the new pressure. They don’t constantly check the pressure and send a signal to the car. My sensors are spot on with my Rhino PSI gauge.

lumberjack | December 6, 2018

I also compared the Tesla sensor output with a good gauge I have (forget the brand name now) a couple of times. They were within 1psi of each other.

Bighorn | December 6, 2018

It has been noted that the car reads low at altitude.

gojones | December 6, 2018

I am at about 4900 ft and the TPMS always shows the pressure between 2-3 psi lower than my very accurate gauge. While having snow tires put on at the SC I asked them about it and was told it is a known issue and can not be calibrated.

rxlawdude | December 6, 2018

An odd thing my wife noticed yesterday. In L.A., temps have been about 20 degrees F lower than "normal," and she called me from the car saying she got a "Tire Pressure Alert" for the front left tire. But ALL the tires were reporting 39psi. I topped all tires off to 44psi (we have an early M3 with 45psi recommended tire pressure), and of course the message was gone.

My theory is that if more than one tire (or all) are low, the warning only presents one of the affected tires.

Has anyone seen the TPMS warning display for multiple tires simultaneously? My lovely bride needs to know. :-)

jwins | December 6, 2018

The inflator(s) might be the culprit. When I was researching these, many reviews questioned the accuracy of some of the popular ones. And the one I bought, in the instructions, said that the tire pressure shown is a couple psi higher than you'll have once you finish the inflation. (Something technical here of which I did not lock onto).

RichardKJ | December 6, 2018

I've seen one, two or three tires reported with low pressure. Never all four. Also, once a tire is reported low the alert remains even if the pressure increases, e.g. from heat. It takes a restart of the car to clear the alert.

rxlawdude | December 6, 2018

Thanks @RichardKJ. It's odd that her warning was for only one tire, when all were at exactly the same pressure.

Toniemoto | December 6, 2018

I live at 5,000 feet and every morning when it's cold I have been getting the tire pressure warning, sometimes for all four tires. I haven't worried about it much because I don't get it when the temps are warmer but I wish there was a way to clear the warning because it is very persistent on my screen. Has anyone figured out how to clear the warning, other than restarting the car?

batmanasb | December 6, 2018

I second @coleAK

"You need to drive a short distance (should be <1 mile) for the sensors to pick up the new pressure. They don’t constantly check the pressure and send a signal to the car. My sensors are spot on with my Rhino PSI gauge."

I noticed my tire pressure slowly going down as it's been getting colder and colder outside, so I went ahead and inflated all of mine to almost exactly 45 PSI according to my Rhino gauge and when checking the car's sensors later in the day, they all showed as 45 PSI. And while I'll need to wait an extra day to confirm, it looks like that brought my Wh/mi down to the upper 200's, when I was getting upper 300's all of the last week.

peldor427 | December 6, 2018

I have seen multiple low tire warnings and I've also seen it were one tire gives a low warning while another tire with the same reported pressure doesn't. I attributed this to round off (i.e 35.8 rounds to 36 and gives a warning while 36.2 also rounds to 36 but doesn't give a warning) or maybe it's a time threshold below a certain point that I don't see.

Anyway, this issue along with the pressure discrepancy between my mechanical gauges and the TPMS (because of my altitude) spurred me to voice in my first bug report while I was driving with the low pressure warning on one tire. I'm sure it was a coincidence, but a minute or two later the warning disappeared. Was someone at Tesla operations monitoring my car and cleared the warning for me when I called it in??? :D