TPMS question

[tireman9]

Received this question from an FMCA member.

I read your great article in Family RVing and appreciate your time and effort for informing readers like me.  I was particularly interested in the side bar about the Advantage Pressure Pro because of the statement you made in your article “selecting a system that can provide an early morning pressure reading”.  Because the Advantage Pressure Pro was in your article does it show an accurate reading before starting to move?  

As yet I’ve never seen this quality as part of a TPMS product description.  When I’ve called a couple of TPMS companies and asked specifically about that, I got an answer that, while positive, didn’t give me a feeling of confidence that I was getting accurate information.  What also makes me a bit wary is that I have a TPMS that came with my 2015 Jeep Cherokee that I bought new.  When I first get in the Jeep I sometimes check the inflation levels.  A couple of the tires will show 36 psi but one or two of the others might show 31 or 32.  Once I drive half a block the low levels come up to 36.  I know half a block is not enough to cause sufficient heating to get the pressure to come up.  Additionally the tires initially showing 36 psi don’t come up a similar increment. With my RV I don’t want to be halfway out of the RV park before I get an accurate reading. 

I don’t know how to prepare a google inquiry to get this information.  Can you tell me how to do that?

OR    Can you tell me how to ask the question of a TPMS supplier so that I get an answer that leaves me more confident about the information?

 OR  Even better yet, can you recommend a TPMS that does this?

 Thanks in advance for your time and effort on this.

Jim Z.

==========================

My reply:

First, you need to know I have no control on the advertising applied to my posts.

 

Some systems require vehicle movement before they will report data (pressure or temperature) some do not require movement. With many dozens of systems on the market, there is no way for me to know what every system does or when a system might change its programming.

 

As I showed in my blog posts different systems will report slightly different numbers BUT as I pointed out, I did not feel the differences were "meaningful".

 

Your Jeep is probably displaying the data from when you parked it. There are two different types of TPM Systems used by Car companies "Active" and "Passive".  Active systems are taking actual measurements of temperature and pressure from miniature sensors. "Passive" systems are calculating inflation based on counting tire revolutions. I don't know which Jeep uses or if they have different systems on different models or year vehicles.

 

If you read all of my Blog posts on TPMS you can see the results of my direct evaluation of two different systems. To my knowledge, this is the only direct comparison anyone has run or published data on.

 

Bottom line I am comfortable recommending either TST system  from TechnoRv or the TireTraker system, directly from Traker.

 

Hope this answers your questions.

[akadeadeye]

Tireman,

As an aside, on a recent trip in August my TST TPMS was showing my left side inside dually (on my motorhome) with 130 pressure and 190 degrees.  The other tires on the same axle were about 110 and 140 degrees.  Is something wrong with my tire or is something wrong with the sensor?  The ambient temp was about 100 degrees outside.

Based on 4 corner weights I run (cold) 105 on the steer tires, and 92 on the drive tires.

Don

Edited December 16, 2022 by akadeadeye

[elkhartjim]

Don, I think you have a bad sensor. Move that sensor to another tire and see how it reads.

[tireman9]

I think elkhartjim's suggestion is a good one. You don't even need to re-program your system just remember which sensor came from which wheel, and switch back after this question has been resolved.

I do think there is a good chance the higher temperature might be due to some external heat source such as the exhaust system. Where is your exhaust pipe?

One other thing to consider. Your "4-corner weights" gave you weight numbers for both ends of the rear axle Do you still have the weights?

Which axle end was heavier?  When selecting your "cold" inflation did you add any "cushion" or is your cold inflation exactly what was indicated by the tables?

Example:  If one axle end measured 8,000#  and the other end measured 9,000#    and the tables for your tire  show you would need 100 pai to support 8,000# and 115 psi

to support 9,000# did you First go with the heavier end and then add 10% to the minimum inflation found in the table?  i.e. 115 psi +10%   or 126 psi?  Also are all the tires on that axle inflated to 126 psi cold? You get the weight. Using the heavier end consult the tables to learn the minimum inflation then add 10% to that number

Finally, your reported 190F is rather high and I would expect overload or defective sensor. Also have you ever done a TPMS System "Test" as I suggested in This blog post?  I bet that almost no one has done a test as I outlined.

[five]

I have cocked my exhaust so that it is canted 45 degrees to the out side of the coach.  Now it does not blow on the RF tire of the toad.

[akadeadeye]

On 12/16/2022 at 6:11 PM, tireman9 said:

I think elkhartjim's suggestion is a good one. You don't even need to re-program your system just remember which sensor came from which wheel, and switch back after this question has been resolved.

I do think there is a good chance the higher temperature might be due to some external heat source such as the exhaust system. Where is your exhaust pipe?

One other thing to consider. Your "4-corner weights" gave you weight numbers for both ends of the rear axle Do you still have the weights?

Which axle end was heavier?  When selecting your "cold" inflation did you add any "cushion" or is your cold inflation exactly what was indicated by the tables?

Example:  If one axle end measured 8,000#  and the other end measured 9,000#    and the tables for your tire  show you would need 100 pai to support 8,000# and 115 psi

to support 9,000# did you First go with the heavier end and then add 10% to the minimum inflation found in the table?  i.e. 115 psi +10%   or 126 psi?  Also are all the tires on that axle inflated to 126 psi cold? You get the weight. Using the heavier end consult the tables to learn the minimum inflation then add 10% to that number

Finally, your reported 190F is rather high and I would expect overload or defective sensor. Also have you ever done a TPMS System "Test" as I suggested in This blog post?  I bet that almost no one has done a test as I outlined.

Exhaust pipe is on opposite side of the coach.

It has been quite a while since I weighed the 4 corners.  I will do so again in case I am packing different than before.  I did assure that I used the psi's from Michelin on all four drive tires based on the heaviest axle end weight.  The same for the steer tires across that axle.  And, I did add 10%.

I will do the "switch sensor test".  That makes sense.  And, I will do the TPMS System Test you provided a link to.

Thank you Tireman.

Thank you elkhartjim.

Merry Christmas to all................

Don