TPMS inaccuracy

[reidmefirst]

I guess PSA: check your tire pressure with a good, accurate gauge if you care about such things. The onboard TPMS seems to be pretty inaccurate, at least on my truck. Probably this is the actual sensors, maybe there is a bad batch? And hopefully the problem will go away when it comes time for me to replace my tires and sensors eventually.

I bought my truck CPO last fall. It's a '21, had 14k miles on it. Factory wheels and factory tires. As winter came on, I checked the pressure and aired up all four tires. I didn't check with my good tire pressure gauge at the time, I just went by what the TPMS showed, what my tire chuck gauge showed, and aired up +5 (tire chuck gauge is about 5 psi higher than TPMS on all my cars, so if I want 30PSI I have to air up to about 35 on the tire chuck). Since then, the onboard TPMS has shown all four wheels at 29/30 when cold. All winter long.

I decided to try and air up the tires a little this spring, just to see if adding a few pounds to each would improve mpg or handling. I pulled out my good accurate tire pressure gauge this time. Lo and behold, my good tire pressure gauge showed all four tires at 19/20psi. Tire chuck on my air compressor showed a bit under 25 on each tire. The dash still showed 29/30.

I aired all the tires up to 34/35 (by the 'good gauge'), the dash now shows 39/40 on all four. Quite a difference. Dash was basically showing +10psi when the tires were at 20, now showing +5psi when the tires are 35. My 'good' tire pressure gauge has been within about a pound of the TPMS readings of our mini cooper and our chevy...so it seems like some of the ford factory sensors might read a lot higher than the tires actually are? It's annoying that the percentage is off by a higher amount, as the actual PSI drops.

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[Rp930]

Mine is VERY close not more than 1 psi off if that.

 

[4x4LAR]

my dash says the tires are all around 34/35 psi but my gauge shows about 32/33. What’s a good gauge anyway? I have a cheap analog one from autozone and thinking of getting a digital one that can be calibrated.

 

[subquark]

I use a Milton stick guage and also the one on the small automatove compressor and it's usually within +/-2 psi from my TPMS.

 

[Canadian Ranger]

I've never looked at my sensors once. Just use a gauge.
I assume the warning will go off though if I lose all the pressure in a tire.

 

[Rinn69]

I have a Longacre 0-60 psi. Comes with 2 "heads" and it's accurate. My TPMS sensors are not factory, yet still read within 1-2 psi of the actual pressure of the tire gauge.

https://www.amazon.com/Longacre-Sta...ocphy=9017973&hvtargid=pla-553831566697&psc=1

 

[ProtonDecay]

We use the truck gauges along with Consumer Pro TPMS they're usually within a pound or two of each other. We use the truck gauges primarily when airing back up after being off-road, as they register new values every few seconds, whereas the CP TPMS is only about every 30 seconds. While going down the road we rely on the CP TPMS as it also monitors the trailer and has more easily adjustable alarms. We try to not obsess over tire pressure variation within about 10% for any given elevation/temperature, and only check for actual level at the start of each day (when cold) - the rest of the time is for pressure and temperature deviation (e.g. the CP TPMS measures valve temperature, which is handy to know if we're differentially heating the truck vs trailer tires while using a lot of braking down steep grades).

Anyway, net-net, for us anything in a range of 37-42 while towing is fine (BFG K02 285/75R17 E).

 

[Tim H.]

I guess PSA: check your tire pressure with a good, accurate gauge if you care about such things. The onboard TPMS seems to be pretty inaccurate, at least on my truck. Probably this is the actual sensors, maybe there is a bad batch? And hopefully the problem will go away when it comes time for me to replace my tires and sensors eventually.

I bought my truck CPO last fall. It's a '21, had 14k miles on it. Factory wheels and factory tires. As winter came on, I checked the pressure and aired up all four tires. I didn't check with my good tire pressure gauge at the time, I just went by what the TPMS showed, what my tire chuck gauge showed, and aired up +5 (tire chuck gauge is about 5 psi higher than TPMS on all my cars, so if I want 30PSI I have to air up to about 35 on the tire chuck). Since then, the onboard TPMS has shown all four wheels at 29/30 when cold. All winter long.

I decided to try and air up the tires a little this spring, just to see if adding a few pounds to each would improve mpg or handling. I pulled out my good accurate tire pressure gauge this time. Lo and behold, my good tire pressure gauge showed all four tires at 19/20psi. Tire chuck on my air compressor showed a bit under 25 on each tire. The dash still showed 29/30.

I aired all the tires up to 34/35 (by the 'good gauge'), the dash now shows 39/40 on all four. Quite a difference. Dash was basically showing +10psi when the tires were at 20, now showing +5psi when the tires are 35. My 'good' tire pressure gauge has been within about a pound of the TPMS readings of our mini cooper and our chevy...so it seems like some of the ford factory sensors might read a lot higher than the tires actually are? It's annoying that the percentage is off by a higher amount, as the actual PSI drops.

Mine is only 1 pound different than my dash gauge. My MPG is within 1 mpg as well after several tanks of gas/adjustment.

 

[rydfree]

I guess PSA: check your tire pressure with a good, accurate gauge if you care about such things. The onboard TPMS seems to be pretty inaccurate, at least on my truck. Probably this is the actual sensors, maybe there is a bad batch? And hopefully the problem will go away when it comes time for me to replace my tires and sensors eventually.

I bought my truck CPO last fall. It's a '21, had 14k miles on it. Factory wheels and factory tires. As winter came on, I checked the pressure and aired up all four tires. I didn't check with my good tire pressure gauge at the time, I just went by what the TPMS showed, what my tire chuck gauge showed, and aired up +5 (tire chuck gauge is about 5 psi higher than TPMS on all my cars, so if I want 30PSI I have to air up to about 35 on the tire chuck). Since then, the onboard TPMS has shown all four wheels at 29/30 when cold. All winter long.

I decided to try and air up the tires a little this spring, just to see if adding a few pounds to each would improve mpg or handling. I pulled out my good accurate tire pressure gauge this time. Lo and behold, my good tire pressure gauge showed all four tires at 19/20psi. Tire chuck on my air compressor showed a bit under 25 on each tire. The dash still showed 29/30.

I aired all the tires up to 34/35 (by the 'good gauge'), the dash now shows 39/40 on all four. Quite a difference. Dash was basically showing +10psi when the tires were at 20, now showing +5psi when the tires are 35. My 'good' tire pressure gauge has been within about a pound of the TPMS readings of our mini cooper and our chevy...so it seems like some of the ford factory sensors might read a lot higher than the tires actually are? It's annoying that the percentage is off by a higher amount, as the actual PSI drops.

Try a re-calibration of the TPMS sensors.

 

[rydfree]

Mine is only 1 pound different than my dash gauge. My MPG is within 1 mpg as well after several tanks of gas/adjustment.

My MPG has always been way off but I've never gotten around to doing the calibration procedure for it . My TPMS is dead on though. At most it may be 1/2 pound out from my accurate guage. I was also surprised at this little Ryobi compressor that I mainly bought for the wife and daughter to use. You select the PSI using the LCD screen and it automatically cuts off when it reaches that pressure. Using that little compressor my TPMS and my good guage all show the same .

https://www.homedepot.com/p/RYOBI-ONE-18V-Dual-Function-Inflator-Deflator-Tool-Only-P747/308746324

 

[Joeiconic]

If you only check your air pressure once a season, that kind of thing can happen. I check mine every week.

 

[JoeC]

I've got a pretty good 0-60 tire pressure gauge, and the truck's TPM is generally about the same.
I will say, especially this time of year, ambient temperature swings can cause my tire pressure to vary by 5 degrees morning to night.
Yea, I take the TPMS with a grain of salt, but it's good enough for government work

 

[subquark]

I've got a pretty good 0-60 tire pressure gauge, and the truck's TPM is generally about the same.
I will say, especially this time of year, ambient temperature swings can cause my tire pressure to vary by 5 degrees morning to night.
Yea, I take the TPMS with a grain of salt, but it's good enough for government work

Same for me here in New England winters. On a 50° F day TPMS says 35 psi, at -10° F those same tires read 29-31 psi (steelies with 255/70/16 Bridgestone Dueler HTs). Kate's low profile YokoLoco tires went from 32 psi to 24 psi.

 

[MrBirdman330]

TPMS is a backup system, it's there to warn you as you drive that a tire is going low and that you should pull over before a blowout happens. It's never accurate usually within a +/- 2 to 5psi variant. It's not a replacement for using a real pressure gauge once a week or at very least once a month. When I stood behind the desk it was like arguing with a brick wall as to the fact their vehicle salesman said they don't have to manually check pressure again. Which I point out if you read the manual it says otherwise. I have to say it's amazing how many people get offended they're told to read an owners manual after their "mechanic" said it was useless.

 

[9zero1790]

mine are pretty close. when i get my air checks and rotation at @Discount Tire my tpms displays the same as the discount fancy machine does. good nuff for me.

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