TPMS readings vs tire gauge: an analysis

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Joined
Nov 2, 2019
Messages
2,180
Location
WA, MT or somewhere else!
RV Year
2018
RV Make
Newmar
RV Model
Mountain Aire 4047
RV Length
40'
TOW/TOAD
2014 Honda CR-V
In getting ready to hit the road this weekend, I did my traditional tire pressure check. The coach had been sitting for several months due to the pandemic, so I was curious what I would find.

We use an EEZ Tire TPMS unit, so I switched it on and let it find all the tires. It was a perfect day to do this; cloudy and in the mid-60s. I checked the tire temperature with a digital infrared thermometer and they ranged from 59 to 63 degrees. A four-degree spread is insignificant, so I was off to a good start.

The TPMS display showed tire temps within a couple of degrees from what I got with the digital infrared thermometer. Again, an insignificant difference. Pressures all read 2-3 pounds under what I regularly set them at (except one that displayed 5 pounds low); not bad after several months of inactivity, but they needed touching up.

So, I broke out the Milton Pro Digital pressure gauge/inflator and fired up the shop compressor. The Milton unit has been checked against two known-to-be-accurate gauges and it has always been spot on. Checking the coach tires, I found them to be 2-5 pounds low; a bit of a difference from what the TPMS showed, but not too bad.

I aired up each tire to the pressure I normally use (Newmar-recommended after four-corner weighing: 110# steer and 85# drive/tag)...plus a half pound. The Milton digital gauge/inflator reads in tenths of a pound, so a half-pound is easily doable. I add the half pound to compensate for the small amount of air leakage that occurs when the TPMS sensor it's screwed on.

I went back into the coach and turned the TPMS unit on again. After allowing time for all the tires to register on the TPMS display (about 5 minutes), I reviewed what I found. All tires were now shown on the TPMS receiver as being within one pound of each other; five read one pound lower than the Milton gauge read and five were the same as what the gauge read. Close, but no cigar when compared to an accurate gauge.

Conclusions.

- A TPMS is a very useful tool for RVers, but it is not a tire pressure or heat gauge; it can be off by 5# or more.

- TPMS sensors on the tires vary in accuracy. Mine were within one pound of an accurate tire gauge, but I have seen them off by 2-3 pounds.

- Carry spare sensor batteries and a couple of spare sensors in case one fails.

TJ
 
Joined
Nov 15, 2019
Messages
500
Location
DFW, TX
RV Year
2020
RV Make
Newmar
RV Model
New Aire 3543
RV Length
35
TOW/TOAD
2020 Jeep Gladiator
I have the same EEZ TPMS that I used on my previous coach, and had the same results. I will reconfigure it for my toad now that I have the New Aire that has the Valor in-tire sensors...although, so far, not impressed with the Valor...still waiting for them to solve bogus false readings.
 

Jim

Joined
Dec 18, 2019
Messages
786
Location
North Carolina
RV Year
2009
RV Make
Tiffin
RV Model
Phaeton QTH
RV Length
40
TOW/TOAD
2016 Jeep Rubicon Hard Rock
In getting ready to hit the road this weekend, I did my traditional tire pressure check.

TJ
Have fun, be safe, and watch out for protesters!
 
Joined
Nov 3, 2019
Messages
405
Location
TGO Titusville FL
RV Year
2015
RV Make
Newmar
RV Model
Dutchstar 4369
RV Length
43
TOW/TOAD
2014 Honda CRV
I just did my sensors yesterday. It was 92F with 90 %humidity. I was dripping wet by the end.
New batteries and new O-rings on all 12 sensors. All I count on the TPMS to let me know that something drastic is going on.
2-3 psi or degrees F, who cares? I don’t 😀
In 7 months all tires were 5 psi low.
Planning for Sunday am liftoff to follow the Snowbirds N.
 
Joined
Nov 2, 2019
Messages
2,180
Location
WA, MT or somewhere else!
RV Year
2018
RV Make
Newmar
RV Model
Mountain Aire 4047
RV Length
40'
TOW/TOAD
2014 Honda CR-V
Had the 2014 Honda CR-V "toad" serviced yesterday in preparation for hitting the road. Got it home and noted on the service invoice that they rotated the tires. Sure enough; checked the TPMS sensors (fortunately, they are marked for the wheel position) and the right-front is now on the left rear, left front on the right rear, etc.). I need to swap the sensors back to their proper positions so the display will show them properly.

Just a heads up that if you have TPMS sensors on the toad and get it serviced, check the sensors positions to be sure they are in the proper wheel positions. And, be sure your sensors are marked so you can tell..

TJ
 
Joined
Nov 3, 2019
Messages
405
Location
TGO Titusville FL
RV Year
2015
RV Make
Newmar
RV Model
Dutchstar 4369
RV Length
43
TOW/TOAD
2014 Honda CRV
Had the 2014 Honda CR-V "toad" serviced yesterday in preparation for hitting the road. Got it home and noted on the service invoice that they rotated the tires. Sure enough; checked the TPMS sensors (fortunately, they are marked for the wheel position) and the right-front is now on the left rear, left front on the right rear, etc.). I need to swap the sensors back to their proper positions so the display will show them properly.

Just a heads up that if you have TPMS sensors on the toad and get it serviced, check the sensors positions to be sure they are in the proper wheel positions. And, be sure your sensors are marked so you can tell..

TJ
TJ, I have the same toad, and had to take it for some repairs. I removed all the sensors and put them in separate ziplock bags marked with the wheel positioning. But it is a good advise on your part.
 
Joined
Nov 3, 2019
Messages
477
Location
Fremont, California
RV Year
2017
RV Make
Newmar
RV Model
Dutch Star 4018
RV Length
40’
TOW/TOAD
Jeep Wrangler Sahara
Yep, I always remove the sensors prior to taking the coach or the toad in for service. I have an engraver similar to this one that I use to number/mark the sensors for position.

 
Joined
Jul 27, 2019
Messages
3,419
Location
Midlothian, VA
RV Year
2017
RV Make
Newmar
RV Model
Ventana 4037
RV Length
40' 10"
TOW/TOAD
2017 Chevy Colorado
Be sure to take them off if going through a car wash. Don't ask!
 
Joined
Nov 2, 2019
Messages
2,180
Location
WA, MT or somewhere else!
RV Year
2018
RV Make
Newmar
RV Model
Mountain Aire 4047
RV Length
40'
TOW/TOAD
2014 Honda CR-V
Be sure to take them off if going through a car wash. Don't ask!
Interesting! You'd think that if they could withstand some serious road spray (especially here in the Pacific Northwest), a car wash would be a piece of cake. Was it a water intrusion issue, or were they pulled off by the rotating brushes?

We had metal valve stems installed on the toad wheels to provide a more durable mounting point for the sensors. And, the tire dealer worked with us to find the proper length stem that allows the sensors to fit snugly into the wheel recess without danger of getting knocked off.

TJ
 
Joined
Jul 27, 2019
Messages
3,419
Location
Midlothian, VA
RV Year
2017
RV Make
Newmar
RV Model
Ventana 4037
RV Length
40' 10"
TOW/TOAD
2017 Chevy Colorado
The issue is the tracks that move your car down the wash. It broke one of mine.
 
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