Final results of TPMS comparison tests

RV Tire Safety
with RV tire expert Roger Marble

Comparison of TireTraker external vs. TST 507 internal TPMS: Summary and my opinion.

Since March I have been conducting a comparison test of two different tire pressure monitoring systems (TPMS). When I started in March the ambient temperatures were down near freezing. I completed my comparison at the end of July with the ambient temperature above 90° F.

I started by checking the accuracy of the various sensor pressure readings. The summary of the test, as reported in this post, indicated there was no meaningful difference between the systems for pressure readings for the 12 sensors I tested.

In this post I confirmed the temperature readings were also essentially the same by comparing the morning readings after a night-long temperature soak.

The next step was to see what the systems reported for the hot running temperatures. I expected that the numbers from the internal system would be higher than the numbers from the external sensors. The reason for this is that the external sensor is actually reading the temperature of the outer end of the metal valve stem that is wiping around in outside air being cooled. The small column of hot air inside the valve stem just can’t transfer enough heat as fast as the metal (brass) valve stem is being cooled off. Here are the numbers. But I had to wonder if the cold ambients might somehow be skewing the data so, knowing I was planning to travel to Indiana in April, Michigan in June, and Wyoming in July, I was hoping that the ambient temperature on one or more of these trips would be significantly warmer than my March trip.

In June I posted my opinion on the value or lack thereof of temperature readings from TPMS. This opinion was not based on any specific results from my testing but just from some serious contemplation to tire temperature recording I had been involved with when working on Indianapolis race car tires and my observations in test laboratories while I worked as a tire design engineer.

Back in May 2012, I posted some actual running temperature images recorded by some high-priced laboratory instruments. You can see the results here. Clearly using a handheld IR gun after you come to a stop or depending on the temperature of the air inside the tire, which is obviously an “average” of the hot and cooler areas of a tire, is not going to give you a reading of the hottest part of a running tire. 

If we are concerned about the advanced warning of a tire failure, tire temperature numbers from a TPMS are not going to be sufficiently precise to identify the temperature of the hot spot. While high temperature can lead to a tire failure, the failure will most likely occur at the hottest spot, which is not the “average” of the internal surface of a tire. Also, extended periods of time at elevated temperature can contribute to the degradation of rubber which could eventually lead to a failure like a belt separation while never being hot enough to set off the high-temperature alarm.

Finally, in July, I could review the results of my readings with higher ambients of the different readings observed with the internal TST 507 system vs. the external TireTraker system.

In mid-August I posted the test results of the external TireTraker system vs. the internal TST system.

OK, so what is the bottom line?

IMO, the performance of the two different systems is similar enough to make recommending one over the other impossible.

There is a cost penalty with the internal system of a little over $100 plus any purchase price difference. Looking at the two different websites I find the 6-sensor TireTraker system with booster available at $398.  The Truck System Technology 6-sensor internal system with the booster is listed at $599. You will need to figure there will be an extra charge to pay for the dismount, mount, and balance of the internal system. I had the TST system installed locally for $109.07 which would bring my total to $708.  To answer the question some of you may have. I purchased and use a TT500 external system and plan on continuing with that system for the foreseeable future. The advertisement you see on this blog does not involve me as it is between any advertiser and RVTravel.com.

Read more from Roger Marble on his blog at RVtiresafety.net.

##RVT861

 

 

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6 Thoughts to “Final results of TPMS comparison tests”

  1. Tommy Molnar

    From reading these articles regarding tire pressure monitors, it sounds like I’m courting disaster if I don’t even HAVE them. I don’t. I check each tire individually before departing on a trip. I ‘thump’ them every time we stop to take a break, and do the same every morning before leaving wherever we’re camped. In over 20 years of RV’ing I’ve had one tire blow out, and that was almost 20 years ago. It was a stock tire that came with the trailer. I buy better tires than come stock on new trailers.

    1. Roger Marble

      Tommy, you are making a reasonable effort but you are obviously missing the time when you are driving. There are other advantages such as eliminating the need to unscrew the valve cap and use your pressure gauge to check the pressure each travel day. The act of checking the pressure in itself may occasionally result in a valve core not completely sealing and you could end up causing your own slow leak. If you check my blog post “Blowout, A real-life experience” I think that is what happened to those unlucky campers.

  2. Alex

    If you choose the TireTracker system and do not have metal valve stems, you MUST install them which will add to the costs. Many trailers, light truck tow vehicles and motorhomes have rubber stems. The weight of the sensor compounded by the centrifugal force of the spinning wheel will flex rubber stems to the point of failure. Whether the result is a gradual or explosive loss of pressure, it is a safety hazard. Unfortunately, the vendor only recommends metal stems and does not explicitly state they’re a requirement. If you include upgrading to metal valve stems, the cost difference between both systems is in the range of $150.

    1. Roger Marble

      Correct though the use of metal valve stems should be standard in all RV applications IMO. Standard “snap-in” rubber stems are only rated for 65 psi max. Also, folks do not think about the rubber in their valve stems “aging out” just as the rubber in their tires ages out.

  3. Dr4Film ----- Richard

    I don’t use either but DO use the Tire SafeGuard TPMS and find it VERY reliable and trustworthy. In regards to temps, take those with caution as the sensor being on the outside of the stem cannot measure the temps inside the tire accurately. It is all relative. If you find one that is GROSSLY out of line with the others then that needs to be investigated.

    1. Roger Marble

      I could only test a couple of systems. IMO almost any TPMS is better than no system. RE Temperature. If in fact the temperature is increasing and is significantly higher in one position for no logical reason i.e. facing the sun all days., I would expect the pressure to also increase and possibly hit your high-pressure warning level.

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