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Accuracy of TPMS?

Barry

Active Member
Aug 9, 2013
1,942
1,621
Colorado
I posted on another thread about the new vehicle status app displaying tire pressure about 4-5 psi low compared with a good quality tire gauge. It's going to become a problem for those of us in climates that are going to be getting colder soon. Should be an easy fix with the next software upgrade.
I just had my tires rotated and the tech added a few lbs of pressure, to 50, as measured by his digianl inline gauge (at Firestone). TPMS shows 48, so not too bad.
DOn't foget the tire pressure changes about 1 PSI for every 10 degrees F, if you're not checking both ways at the same time.
 

AudubonB

One can NOT induce accuracy with precision!
Moderator
Mar 24, 2013
8,907
37,796
Few of us have the equipment necessary to determine the accuracy of our gauges; I do what AWDTsla does, but the naked truth is that all such devices could be equally wrong.

Nevertheless -
Creating a device to respond to relative gas pressures is not, as it's fun to say in these forums, rocket science. As such, if one has three or even two pressure gauges that agree with each other, there is an excellent chance they are correct.

All of this brings to mind Joe Pesci's and Marisa Tomei's characters in My Cousin Vinny:

Lisa: [sighs] If you will look in the manual, you will see that this particular model faucet requires a range of 10 to 16 foot-pounds of torque. I routinely twist the maximum allowable torquage.
Vinny Gambini: Well, how could you be sure you used 16 foot-pounds of torque?
Lisa: Because I used a Craftsman model 1019 Laboratory Edition Signature Series torque wrench. The kind used by Caltech high energy physicists. And NASA engineers.
Vinny Gambini: Well, in that case, how can you be sure THAT's accurate?
Lisa: Because a split second before the torque wrench was applied to the faucet handle, it had been calibrated by top members of the state AND federal Department of Weights and Measures... to be dead on balls accurate!
[She rips a page out of a magazine and hands it to him]
Lisa: Here's the certificate of validation.
Vinny Gambini: Dead on balls accurate?
Lisa: It's an industry term.
Vinny Gambini: [tosses paper away] I guess the ****** thing is broken.
 
Creating a device to respond to relative gas pressures is not, as it's fun to say in these forums, rocket science. As such, if one has three or even two pressure gauges that agree with each other, there is an excellent chance they are correct.
But here's the rub, three cheap analog gauges (2 of the simple pen style slide-out ones, and one that is part of the filling assembly on my air compressor) all agree at one number, the 4 TPMS sensors all agree at a different number 5psi different...

I'm inclined to believe the TPMS, but it does lead one to think...
 

CHG-ON

Still in love after all these miles
I have read that some see their TPMS reading a few pounds less than their tire gauge. So I did the most simple test. I filled my tires to exactly the spec for my car, very carefully, with what I think is an accurate gauge (according to tons of Amazon reviews...). 38 front, 40 rear. I then drove just far enough to get the sensors to report (less than 1/4 mi) on a very cool day with no sun on the road and slowly. They gave the exact same reading as my gauge. I was actually quite surprised. However, when I bled my tires dry in order to put AlloyGators on, the alarm did not go off until they were essentially completely flat. So I don't trust their ability to warn me that I am low, only that I am flat, which is WAAAAY too late. What's up with that? My '06 Acura would warn after a 10% drop in pressure. So I check the widget regularly. I will say that the tires don't seem to lose pressure except when the temp changes significantly. I expected that they would.
 

jerry33

(S85-3/2/13 traded in) X LR: F2611##-3/27/20
Supporting Member
Mar 8, 2012
20,440
27,189
Texas
So I check the widget regularly. I will say that the tires don't seem to lose pressure except when the temp changes significantly. I expected that they would.

Modern tires with oxygen-tight butyl tubeless liners don't lose pressure unless the liner is damaged or there is a leak somewhere else (wheel or valve).
 

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