Community Forums

jimws · 09-23-2016, 09:10 PM

I have the TST 507 monitor system for my 5er & truck. I also have 2 good digital tire pressure gauges.

The 2 digital pressure gauges read within 1/2 # of each other. The TST system consistently reads 3 to 4 # lower, depending upon the tire, than the 2 gauges.

Questions:
1- Anyone else experience this?
2- Which do you trust?

**JohnRR** · 09-23-2016, 09:24 PM

Im not looking for precise accuracy with the TPMS just compatible readings while driving. You can't check what's happening while your driving even with the best most accurate pressure gauge.

dabrooks · 09-24-2016, 04:25 AM

My TST 507 system reads within 1lbs of my gauge. But John is right. I watching the pressures as I am driving to insure they stay consistent with each other. I do check the TST every morning before I start out but I know they read 1lb low so there is no issue with me. At 1lb or 4lbs there wouldn't be an issue any way as long as you know the difference.

Dr4Film · 09-24-2016, 04:33 AM

Any TPMS regardless of brand will generally not be as accurate as your calibrated tire psi gauge PLUS it doesn't have to be. The sole purpose of a TPMS is warn you of a slow leak so you have time to correct the problem.

If not running with a TPMS and you do have a slow leak you WILL destroy the tire and possibly much more once the tire self destructs from heat.

Dr4Film ----- Richard

Chuck_Hammer · 09-24-2016, 04:35 AM

if available, calibrated would be very pricy... and NOT needed.

just make a note of difference... and monitor for a Change,, NOT value.

looking for air leak,, or heat buildup.
.

nosticks · 09-24-2016, 05:27 AM

There is an old saying, "a man with two watches is never sure what time it is". The same for two tire pressure measurement devices. Just pick one over the other and stay with it for consistency.

georgelesley · 09-24-2016, 05:27 AM

+1 to all the above. Tpms just tells you about changes. If you try to get it exactly like your accurate gauges you will be chasing air temps the rest of your RV life. (Don't ask me how I know this)

MSHappyCampers · 09-24-2016, 12:51 PM

TPMS and tire pressure gauges serve two entirely different purposes!

I don't worry that the TPMS is not accurate, just that it does it's job when needed!

greystroke · 09-24-2016, 01:31 PM

Pressure Calibrations are usually performed with Dead Weight Testers (DWT). They have a calibrated cylinder where for a given force on the cylinder produces a given pressure when the cylinder is suspended. To be calibrated the DWT must have traceability to NIST(National institute of Standard Labs) previously known NBS (National Burea of Standards)

To my knowledge the DWT is still the most accurate and repeatable device. At least it was when I performed pressure calibrations years ago. It is accurate and repeatable since it directly uses the formula Pressure = Force/Area.

All that said I use two standard(non-digital) analog pressure gauges and usually split the difference between the two readings. Best I can do without paying for an expensive calibration. I use the analog devices because it more closely uses the Pressure = Force/area concept and although the readings may change over time due to wear, I feel they are my best bet.

Other devices such as pressure sensors or bourdon types have to go through or traceable to a DWT and then on to NIST. The readings can go off if the sensors have malfunctions.

Tire pressures calibration is a waste of time. If there close and don't change much during trip your good to go. I just compare the TST sensor pressures to the avg of two analog gauges. That gets me close.

bobk3d · 10-02-2016, 09:59 AM

More probable than than not, somebody is deflating your tires. After measuring air pressure with multiple uncalibrated gauges, that was the conclusion reached by the NFL.