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      05-02-2018, 02:49 PM   #1
WallySlash
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How Accurate is TPMS

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I am thinking that the TPMS isn't as accurate as my digital tire gauge but wanted to get some feedback.

I filled the tires to spec (32psi front, 35psi rear) and checked with a digital tire gauge but the TPMS was showing about 1 psi higher for each tire. Fronts showed 33.2psi and the rears showed 36.3psi

The car was in the garage sitting for a few days prior so I would suspect the ambient temperature was the same for all four tires.
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      05-02-2018, 06:00 PM   #2
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My TPMS shows about 3 psi lower for each tire. I would go by a gauge you trust and not the TPMS.
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      05-03-2018, 02:53 AM   #3
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Arenít you supposed to reset the TPMS every time you fill tires? At least that was my experience in the past.
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      05-03-2018, 04:19 AM   #4
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Quote:
Originally Posted by WallySlash View Post
I am thinking that the TPMS isn't as accurate as my digital tire gauge but wanted to get some feedback.

I filled the tires to spec (32psi front, 35psi rear) and checked with a digital tire gauge but the TPMS was showing about 1 psi higher for each tire. Fronts showed 33.2psi and the rears showed 36.3psi

The car was in the garage sitting for a few days prior so I would suspect the ambient temperature was the same for all four tires.
Before you can judge the accuracy of TPMS, you have to think about your gauge. As it does depend on how accurate your gauge is, what side of the design tolerance it is reading. Recently calibrated?

For me it is more about first comparisons and how consistent the readings are over time. I know one of my gauges reads about 1psi low in the pressure range I'm using, against a calibrated gauge. I simply allow for it.
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      05-03-2018, 11:16 AM   #5
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With any gauge / sensor you need to consider;

Resolution: (if digital - is it giving a result in single psi increments, half psi, tenth of a psi etc, if analogue - what spacing is there between psi markings to allow correct reading of the gauge by eye)
Accuracy: how close to the actual value is the gauge / sensor showing?
Repeatability / Reliability: for a given value will the gauge show the same on each occasion.

Many people mistake resolution for accuracy.

Given the values of pressure that are recommended by the manufacturer vary widely depending on two broad categories of weight and we choose to either run at one, the other or somewhere in between; do we need high accuracy?

Given that TPMS seems to also measure and utilise temperature in it's thinking , it's my preference to go with the TPMS pressure as being 'accurate'
There I go using the word accurate...hmmm

The Reset of the TPMS 'pressure' after adjusting your tyre pressure is to tell the TPMS that this is the correct pressure you want it to watch for and warn you about, should it go out of specification (low).

It's certainly stopped me being concerned that I might be losing pressure during long drives after hitting a pothole for instance, where previously I might have felt the need to stop and check.
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      05-03-2018, 12:23 PM   #6
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I agree, you canít really trust the accuracy of your gauge unless youíve verified it against a known correct reference. I havenít done that with my gauges, but I have 3 gauges and they all read very close to each other so Iím going on the principle of triangulation to assume that means theyíre reasonably accurate.

I would also put a little more trust in a gauge that claims ANSI calibration, or one from a racing equipment company.

Hereís one that I have that claims ANSI calibration, which tracks pretty closely with my digital gauges.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
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      05-03-2018, 12:52 PM   #7
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my TPMS readout is usually within 1 lb of my 2 digital gauges. Dont really rely on it for grainular accuracy, but rather for a significant change in pressure warnings. It is fun to watch the changes as the temp increases.
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      05-04-2018, 03:12 AM   #8
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Quote:
Originally Posted by WallySlash View Post
I am thinking that the TPMS isn't as accurate as my digital tire gauge but wanted to get some feedback.

I filled the tires to spec (32psi front, 35psi rear) and checked with a digital tire gauge but the TPMS was showing about 1 psi higher for each tire. Fronts showed 33.2psi and the rears showed 36.3psi

The car was in the garage sitting for a few days prior so I would suspect the ambient temperature was the same for all four tires.
Highly accurate on my 3. Never a problem. Verified with a calibrated air gage. Spot on.
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