TPMS sensors vs. 4 different pressure gauges

[blujay40]

I have had a TST507RV system with the flow thru sensors for about a year now. One thing I have noticed is that there seems to be a 5-6# discrepancy between the TPMS readouts and whatever other method I use to measure tire pressures.

For instance, prior to our 1500 mile trip back from our seasonal site to home a few weeks ago, I checked tire pressures on our TT. The TPMS system showed all 4 tires at 74-75#.

So I got out the Viair and grabbed the attachment that has a built in pressure gauge and screws onto the valve stem. As soon as I attached it, the gauge on the Viair measured 80# exactly, which is what the cold pressure should be. All 4 tires came back right on the money.

So out of curiosity, I pulled out two other handheld pressure gauges I have, one digital and one analog and both of them registered 80# as well. I then went to our parks air station before leaving for yet another check and it also read 80#. Given that I now had 5 different measurements with the TPMS reading being the anomaly, and the other 4 showing the exact same reading, I began to question the accuracies of the sensors.

So I emailed TST and asked them about this.

"Most hand held gauges are accurate to 3-5 PSI, the sensors will be accurate to 1-2.5 PSI".

So which pressure reading(s) would you believe? The TPMS sensors or the 4 other gauges that all consistently match?

[norty1]

My TSPS sensors are usually about 1-2 psi lower. I have noticed that no matter what the cold pressure is when I start out they rise to about the same temp when on the road.
It is a puzzlement though.

I have had a sensor that seemed to be intermittent and I tightened it just a little and it then worked well.

[blujay40]

Yeah, the sensors clearly work because the TPMS temps and pressures change as expected due to tires heating up, sun side vs. shade, etc. I had also just removed all the sensors, installed new batteries, and reinstalled the sensors with the same outcome.

I still go with what the gauge on the Viair says vs. the sensors when filling the tires to the proper pressure.

[hoppers4]

My 507s read 2-4 lbs lower than my external gauge. I air up according to the external gauge.

[jimp]

I had posted a similar question in another thread I started about TPMS's on this issue about the accuracy of the sensors vs other gauges.

I have a TST 507 with screw on cap sensors, not flow thru. My TST sensors read about 6-7 psi lower than 2 other gauges I have/use at cold temp, and was wondering which gauge reading others were using to determine their cold psi setting.

[norty1]

I rely on my digital sensor. The mechanical ones are not as dependable.

I like to read the pressure on a digital indicator instead of a stick.

[prm99v6]

I have the same problem with the tireminder brand. All 10 sensors 6psi higher than three other gauges that all read the same. I even put one of the gauges on a different vehicle with built is TPMS and the readings matched the vehicles on board sensors.

TPMS has been around long enough that there shouldn’t be a delay on the sensors and they should be more accurate. At the very least the monitor or app in my case should allow users to adjust the baseline for variances in sensors.

[wabirch]

I guess so long as a pressure rise or drop is accurate, the change is what I want monitored even if the actual is off a bit.

[RedHorse1]

An interesting observation, was airing up the tires today and tried all 4 xmitters on the same tire.
I saw about 3psi difference between them and all were lower than my mechanical gauge. As a side note my 12v compressor read 118# and the mechanical was 110#, which was the target.
My go to pressure measurement is the mechanical. Everything else is a reference point.

[mikefos]

My 4 TST 507 screw-on sensors are 2# lower than both my digital gauges, so I just compensate for that. If I want 70# to be the baseline for the sensors to monitor from, I fill the tires cold to 72# on my digital gauge and go with it. Close 'nough.

[vikefan7]

Sorry to hijack, but are these things worth the money and would the work with a 35' fifth wheel with a crew cab short bed Ram without a repeater?

[mikefos]

Sure, I have a 35' TT and a long bed crew cab TV, with no repeater. Try it.

Worth it? You bet. One blow out can easily do some big time damage/cost to your rig.

[Force]

Just to pile on to everyone's observations, my mechanical gauge is always within 1-2# of what my truck display says each tire has for pressure, and my bicycle pump gauge is about the same (if price is any measure, both should be pretty good gauges).

My flow thru TPMS sensors on the other hand always report they are 4-5# lower than what my mechanical gauge says each trailer tire has.

So now if the TPMS says I have about 75 PSI I'm good to go as it's actually at the 80 PSI the tire calls for per my other guages

It would be nice to have an offset / correction option on the TPMS display.

[norty1]

Originally Posted by vikefan7

Sorry to hijack, but are these things worth the money and would the work with a 35' fifth wheel with a crew cab short bed Ram without a repeater?

My TST unit works great with no repeater. See my sig. I'm almost 4' longer.