TPMS or my Tire Gauge likely off

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KandT

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Both new - Tire gauge reads 105.  TPMS reads 119 - Big difference.  Reads the about the same difference on all the tires.

Ambient air temperature reads above 50 for hours.  TPMS says the tires are in the low 40's.  Shouldn't they be hotter than the air temp?
 
KandT said:
Both new - Tire gauge reads 105.  TPMS reads 119 - Big difference.  Reads the about the same difference on all the tires.

Ambient air temperature reads above 50 for hours.  TPMS says the tires are in the low 40's.  Shouldn't they be hotter than the air temp?
Click to expand...

If you are driving, they will be hotter. If you are just parked, whatever the outside/ambient temperature is, that's what the tire temperature should read.
I would check the pressure with another gauge.
 
Only to potentially help, what brand/model of TPMS are you using?
Could be a known problem with whatever mfr it is.
 
That is a too-big spread, but even good air gauges are only accurate to within 3-5%%. If your gauge is reading 5% low and the TPMS 5% high, that could explain a big chunk of it. You need to get some additional measurements and try to determine how close each gauge is.  Your TPMS has a separate sensor at each wheel, so that gives you multiple samples to compare right there, but I would want to compare your portable gauge to another device as well. Maybe a local tire shop would let you take some comparisons to their gauges.

 
Man with two watches never knows what time it is.  Old Chinese Proverb.

As an Analytical Chemist, any measurement device is evaluated for PRECISION  and ACCURACY.  Assuming all tires are inflated to the same pressure, the precision of the TPMS appears pretty close (multiple measurements, similar result).  However the accuracy of either the TPMS or gauge is off (Actual, true value vs measured value).  As suggested, the best way to decide is to measure with 3 or 4 other gauges and see what you get.  Hopefully, one will be a clear outlier.

Since the precision is good, once you determine the true reading, simply add or subtract the difference, and you are good.  That can be a pain, but when traveling, what you are looking for is a big change more than actual pressure.  It may also be possible to recalibrate the TPMS if it is in error.

Personally, this issue would drive me nuts!!  (And it could be a very short trip)  ;D
 
Gee. I have several wartches but only two I can still wear (the others are used as "Wall clocks" since the case is damaged and not worth fixing so I can not attach a watch band any more)

Both of the wearable watches give exactly the same time to within a very tiny fraction of a second (too samll for the eye to detect)  Always dead on.. and there is a 3rd clock in Colorado that also tells the exact same time (Again with the same error rate)

Last time I checked the one I AM wearing was 15 bucks and the Dress Watch about 20 or 25 from MFJEnterprises (I think, google MFJ)

OH, the one in colorado.. WWV's Atomic clock. That is the "Master" mine are slaves (WWV sets them for me)
 
KandT didn't say whether that 119 was a single reading or all 6 tires the same. Each sensor sends it's own value, and each sensor is subject to accuracy variations. Of course, they share the same design, so if it's a design flaw they all have it.

In this application, +/- 3% is considered good accuracy, which basically means adequate for the task.  However, that means two "good" gauges could differ by as much as 6% in their readouts. One might be 3% low, showing 97 on a 100 psi tire, while another is 3% high at 103 on the same tire. That's still a far cry from the 14 psi difference in this case.

The Accutire digital gauge has been shown to be well within the "good" category in numerous tests by outfits like Consumer Reports, car magazines, etc.It seems to stay accurate after years of use as well, another big plus.
 
Hmmmm...  sounds like a new gauge to solve this delema.  My other is new as well but could have a flaw as all the TPMS gauges read pretty close to 119. 

As for watches - the best times are when you don?t need one!!
 
that's the reason I don't like digital gauges for things like this.  Too easy to get hung up on the ones....or even the tenths!
It drives me nuts when my TPMS is off side to side by even a negligible amount.  I wish it was analog for my sanity!
 
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