TPMS accuracy

[Stuart W]

I have installed TirePatrol TPMS on my DS. prior to the installation of the pressure sensors I inflated the tires and verified the pressure at 115 with two different digital gauges. The difference between the system readout and the gauge readings is 6 PSI higher on the two front sensors on the system. Is this normal? Thanks Stuart

[cruzbill]

Similar thread here a couple of weeks ago. I would call the mfg and let them know, they should send you replacement sensors. Usually they say 'accuracy' is +or - some percent. Well if you are running 100psi in you steer, 5% would be 5 psi, so you are pretty close already. I've also seen accuracy stated as +- 1.5 psi. That's within 1.5%, darn close. In reality, a TPMS is not to be used as an accurate tire pressure gauge, but as a warning device to tell you when your tire pressures CHANGE. So keep your tire gauges and use them to check your tire pressures. Keep the TPMS on to track the change in pressure over time, not the actual tire pressure values.

[Stuart W]

Originally Posted by cruzbill

Similar thread here a couple of weeks ago. I would call the mfg and let them know, they should send you replacement sensors. Usually they say 'accuracy' is +or - some percent. Well if you are running 100psi in you steer, 5% would be 5 psi, so you are pretty close already. I've also seen accuracy stated as +- 1.5 psi. That's within 1.5%, darn close. In reality, a TPMS is not to be used as an accurate tire pressure gauge, but as a warning device to tell you when your tire pressures CHANGE. So keep your tire gauges and use them to check your tire pressures. Keep the TPMS on to track the change in pressure over time, not the actual tire pressure values.

Thank you, what throws me is on my Harley I have had a system for 3 years and I can set the tire pressure, screw on the sensors and it is always the same, so I would say les then .5 PSI @ 40 PSI. Much closer to the 1 to 1.5%

[cruzbill]

Yep, I'm sure there is variability brand to brand. One thing is that the TPMS made by TireSafeGuard has a 'offset' adjustment (I've read) so you can zero in on your actual tire pressures. Like I said though, its for changes in pressure not to measure the actual tire pressure.

[Stuart W]

Originally Posted by cruzbill

Yep, I'm sure there is variability brand to brand. One thing is that the TPMS made by TireSafeGuard has a 'offset' adjustment (I've read) so you can zero in on your actual tire pressures. Like I said though, its for changes in pressure not to measure the actual tire pressure.

With settings for high and low pressure I would like to see it closer. Otherwise you have to enter an inflated (no pun intended)value for the alarm to be accurate

[Stuart W]

Ok came back out to the RV an hour later and pressure was with in one PSI so there must be an equalization period. All is good now, thanks for your help stuart

[Sky_Boss]

Originally Posted by Stuart W

Ok came back out to the RV an hour later and pressure was with in one PSI so there must be an equalization period. All is good now, thanks for your help stuart

I will toss this out...

I'm ASSUMING you are talking about your front tires. I'm not to sure drive and/or tag axle need anything close to that.

Anyway...

The TPMS sensor screws on the stem and depresses the core plunger. At 115 PSI the core plunger is more resistant to that pressure. I'm suspecting that the sensor is not sufficiently depressing the plunger. I'm basing that on similar experience for my steerer tires at 115 PSI also. My solution was to back the core out about 1/4 turn.

BTW...I've seen this happen on lower pressures but much less so. In those cases I did the same and problem solved.

YMMV

[Stuart W]

Originally Posted by Sky_Boss

I will toss this out...



I'm ASSUMING you are talking about your front tires. I'm not to sure drive and/or tag axle need anything close to that.



Anyway...



The TPMS sensor screws on the stem and depresses the core plunger. At 115 PSI the core plunger is more resistant to that pressure. I'm suspecting that the sensor is not sufficiently depressing the plunger. I'm basing that on similar experience for my steerer tires at 115 PSI also. My solution was to back the core out about 1/4 turn.



BTW...I've seen this happen on lower pressures but much less so. In those cases I did the same and problem solved.



YMMV

That great information, yes only the fronts are at 115 backs at 85

The fronts I’m having to use a small extender for the sensor to clear the wheel and suspect your theory may apply. Going to let it sit for the night and recheck in am. Thanks.

[Sky_Boss]

Originally Posted by Stuart W

That great information, yes only the fronts are at 115 backs at 85

The fronts I’m having to use a small extender for the sensor to clear the wheel and suspect your theory may apply. Going to let it sit for the night and recheck in am. Thanks.

That doubles the recommendation. LOL The extenders can create similar dynamics. What I suspect is that over time the pressure equalized between the core and the sensor and/or extenders.

[FLJOE]

Different manufacturers may give you different results. My TST 507 system, which I recently updated and had to add more sensors, had always been within 1 - 3 psi of my digital gauge.