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Accuracy of TPMS?

NJEV-Don

Member
Sep 10, 2020
328
197
Northern New Jersey
Curious what people think of the accuracy of the MY TPMS. I adjusted the tires on my 19” Gemini tires to 42 PSI per the recommendation. The car says it’s 44-45 for each tire. My tire gauge is supposed to be accurate. The ride is pretty rough so thinking the TPMS may be more accurate. Thoughts? Anyone have better experience with different tire pressures? Thanks for anyone responding.
 

frankvb

Supporting Member
Supporting Member
Feb 29, 2020
927
574
San Diego, CA
Yesterday I inflated the tires to 41 psi (checked with an accurate pressure gauge) and the car is showing 41 psi on all wheels.

I'm not sure if the car pressure reading is adjusted for tire temperature, so that may have caused the difference? Or, if it is, it would show the pressure at 70F or so, which means if you inflate it at very low temperatures it would show a too high pressure.
 

jcanoe

Active Member
Oct 2, 2020
3,526
3,563
Maryland
The pressure readout on the TPMS on my Model Y with 19" Gemini wheels and OE Continential tires match my Intercomp 2.5" dial Deluxe Air Pressure Gauge (analog gauge) within 0.5 lb. Tires need to be cold (at rest for ~4hours) when checking the tire pressure. If one side of the vehicle is being warmed by the sun the tires on that side will read at least 1lb higher that the tires that are in the shade. A garage reading is best, first thing in the AM. The TPMS in my Model Y will provide a reading almost as soon as I start driving, the reading is consistent after ~1 mile of driving. Later readings will typically be 1 to 2 lbs higher than when cold. Usually all 4 tires will read the same with one tire reading lagging by 1 lb until it warms up.
 
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Jacko

Member
Sep 17, 2020
74
36
portland, or
Curious what people think of the accuracy of the MY TPMS. I adjusted the tires on my 19” Gemini tires to 42 PSI per the recommendation. The car says it’s 44-45 for each tire. My tire gauge is supposed to be accurate. The ride is pretty rough so thinking the TPMS may be more accurate. Thoughts? Anyone have better experience with different tire pressures? Thanks for anyone responding.
I have a MY Performance and the TPMS on the 21s were dead on. I just swapped to my winter setup - Martian Wheels/Vredestien tires and a new set of Tesla TPMS. Also dead on. I'm using a very accurate digital gauge. And the MY read the new TPMS as soon as I drove out of the tire shop.
 

Srad600Volt

Member
Sep 28, 2020
347
249
Southern California
I have a pretty accurate digital tire pressure gauge and the TPMS is usually within a half pound of the gauge. The TPMS only indicates full pounds, so there is some roundoff happening, my gauge reads down to 0.1 lbs.
 

Srad600Volt

Member
Sep 28, 2020
347
249
Southern California
what tire gauge do you have?
Longacre Racing Products 0-60psi digital tire pressure gauge.
IMG_0806.JPG
IMG_0807.JPG
 
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kindofblue

Member
Mar 14, 2021
111
73
Pismo Beach CA
Sorry, just created another thread after my search didn't bring this one up. Here's my post there as I can't figure out how to delete that other threat I just posted:

The TPM on our 2021 Y has consistently read 42 psi. I checked it a couple days ago before heading out on a road trip and the accurate tire pressure gauge read 40 to 40.5 psi. When I used a calibrated air pump to put them to 42.5 for the trip the TPMs then read 45 psi. Just wanted to alert others to this discrepancy.

Given our different experiences I think it prudent to "trust but verify" the TPMS readings.
 

jcanoe

Active Member
Oct 2, 2020
3,526
3,563
Maryland
Sorry, just created another thread after my search didn't bring this one up. Here's my post there as I can't figure out how to delete that other threat I just posted:

The TPM on our 2021 Y has consistently read 42 psi. I checked it a couple days ago before heading out on a road trip and the accurate tire pressure gauge read 40 to 40.5 psi. When I used a calibrated air pump to put them to 42.5 for the trip the TPMs then read 45 psi. Just wanted to alert others to this discrepancy.

Given our different experiences I think it prudent to "trust but verify" the TPMS readings.
So are all four TPMS reading higher than the tire pressure gauge? Do have any powered device plugged into the front USB-C ports, the Tesla Model Y Owner's Manual contains a note that powered USB devices, i.e a hub, can interfere with the TPMS.
 

Silicon Desert

Active Member
Oct 1, 2018
3,665
3,754
Sparks, / GF1
I have a pretty accurate digital tire pressure gauge and the TPMS is usually within a half pound of the gauge. The TPMS only indicates full pounds, so there is some roundoff happening, my gauge reads down to 0.1 lbs.
You may know this, but many people don't. Just because the "resolution" of the gauge shows in tenths of pounds, it does not mean that is the accuracy. As with any gauge there is a combination of resolution, accuracy, and repeatability. 3 different potential variables. One example I think of is that many of the human temperature reading devices on the market show your temperature in tenths of a degree, yet the accuracy is typically plus or minus .2 or .3 degrees. Some of those things are terrible can be off plus or minus 1/2 degree but lead you to believe they are accurate because they show in tenths.

So what is is actual accuracy and repeatability spec of your device? NOT what it shows as the resolution.
 
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kindofblue

Member
Mar 14, 2021
111
73
Pismo Beach CA
So are all four TPMS reading higher than the tire pressure gauge? Do have any powered device plugged into the front USB-C ports, the Tesla Model Y Owner's Manual contains a note that powered USB devices, i.e a hub, can interfere with the TPMS.
To your question, no. And I took the readings in the garage in the early a.m w/cold tires.
 

Silicon Desert

Active Member
Oct 1, 2018
3,665
3,754
Sparks, / GF1
Curious what people think of the accuracy of the MY TPMS. I adjusted the tires on my 19” Gemini tires to 42 PSI per the recommendation. The car says it’s 44-45 for each tire. My tire gauge is supposed to be accurate. The ride is pretty rough so thinking the TPMS may be more accurate. Thoughts? Anyone have better experience with different tire pressures? Thanks for anyone responding.
Let's keep in mind here about the main purpose of a TPMS. It is to warn of low pressures that can be dangerous for driving. Most of them are not really that accurate and generally plus or minus 3% accuracy. Of course it varies by brand. And then when you add in the variation of the external device being used to measure the pressure, you will see variances, sometimes as much as 2 PSI, but typically might be within 1 psi. This all assumes you are making measurements within a short period of time and not driving the car long distances. Remember that temperature is a big variable.
 

jcanoe

Active Member
Oct 2, 2020
3,526
3,563
Maryland
To your question, no. And I took the readings in the garage in the early a.m w/cold tires.
If only one of the TPMS sensors is reading high then it could just be normal variation in the sensitivity, accuracy of the TPMS sensors. The left front TPMS sensor on my Model Y consistently reads about 1 lb lower than the true tire pressure as confirmed with the other three TPMS sensors and my Intercomp tire pressure gauge. It could also be due to be interference with the TPMS signal from that tire location.
 
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