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Friday, May 23, 2014

What is the "Best" TPMS

Yes along with   What is the "best" brand tire or Best RV or maybe even the Best pizza, people seem to think that there is a single answer to almost every brand selection that everyone will agree on.

 As an engineer I feel that just as Henry Ford was wrong when he decided everyone would want a black car, there is seldom a "Best" anything that is the best for everyone. However, having said that, you probably still would like some guidance in selecting a TPMS.

NOTE: I am certain that ANY brand TPMS is better than not having a system.

So here is what I suggest you use for a selection system. I think this will be a good system to use even as the technology moves forward.

I think there are four major categories to use when shopping for a new or replacement system.

1. Performance:  What does the system do and how well does it do it?

2. Cost:  This includes more than just the initial purchase price as there may be the cost of installation and what about the batteries?  When looking at cost I suggest you do a comparison based on the expected replacement cost of replacement sensors if you can't install batteries yourself.
Example - non-replaceable batteries last 5 to 6 years so include the cost of a set on new sensors vs the cost of replacing batteries every two or three years. (three sets at $1.50 per battery for example). Selection of an internal mount system will include the cost of the initial dismount and mount and balance of tires and a second dismount, mount and balance when the sensors need replacement a few years later. This cost could exceed the cost of a TPM system so is an important consideration

3. Warranty:  This may be the easiest as I prefer a longer warranty to a shorter one. I believe that car manufacturers do a much better job of designing and building their product than does the RV industry. Given the prevalence of 3, 5 and even 10 year warranties for cars vs the normal  few months offered by those selling RVs products with longer warranties are more likely to be better than those with short warranties.

4. Support & Service:  How easy is it to contact the seller? Are there videos on YouTube showing how to install and program your TPMS?

Items 2 through 4 are best left to you to learn and investigate. Some people don't care about YouTube videos and others don't worry about warranties, so lets focus on "Performance"

Here are some questions to consider:
a. Does the system "talk" to your on-board video display? This may lock you into one brand to the exclusion of all others.

b. Accuracy:  Some people are overly concerned with the accuracy of the TPMS. Personally I have observed that after setting my tire cold pressure using by calibrated digital hand gauge I see that the TPMS gives slightly different numbers for almost every tire BUT the difference is usually only a couple psi. While this may be measurable I don't consider it meaningful. You might want to review the concept of Measurable vs Meaningful. You could also review my comparison of two systems HERE.

c Temperature vs pressure checking. Most aftermarket systems will signal both pressure and temperature. Some people think temperature is very important but as a tire engineer I believe that if you have the proper load and inflation you do not need to worry about temperature variation and can expect to see operating temperatures range from +15°F to +50°F above ambient. Many TPMS have a warning temperature of between 150 and 160°F which is OK in my opinion for a warning level. It is very unlikely for you to have a tire get hot without having a loss of air precede the increase in temperature.

d. Early warning:  I consider this an IMPORTANT and desirable feature
Imagine your cold pressure is 100 psi. Your low pressure warning is probably -15% or 85psi. When driving you might have a hot pressure of 120 psi. Now suppose you get a leak from a puncture or possibly a valve stem gasket leak. Would you rather get a warning when you loose 3 or 6 psi over a few minutes down from the 120 psi HOT pressure, or would you think it OK to only be warned after you loose 35 psi down from the hot pressure to the "Low Pressure Warning" level.?

In my opinion getting that "Early Warning" allows you to slow down and start looking for an exit or safe place to pull over as you monitor the air loss over then next 5 to 20 minutes you might have before you get down the the minimum pressure needed to carry the load.

Sometimes the rate of air loss can start small but increase over a few minutes as the hole in the tire gets bigger. If you only get the single warning it may already be too late to save and repair the tire.

I hope I have given you some things to consider when selecting the "Best for you" TPMS.



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5 comments:

  1. When I first got our RV I knew I wanted a tire pressure/temp monitor and it has proved invaluable. At first I was bugged by it not being exact as my digital pressure guage. I would get all 6 tires right on and then go turn on the system and see that they all varied 1 or 2 psi....But when one of my valve stems started leaking it was great to notice that and be able to pull over to fix the problem. I have gotten used to the sensors to not all being the same. I now just look for extremes and that is really all we need. Think about the days without any sensors....so I had to get over the non-exactness and be happy to have the warning available. I am German and being exact is in our DNA...ugh!

    ReplyDelete
  2. Anon, Glad you have come to terms with non-exact numbers. People need to remember these are primarily Early Warning Devices.

    I have two different systems and two digital hand gauges that have been checked against ISO Lab master gauges. Between 12 TPM and 2 gauges I have a pressure range of +/- 1.5 psi even when the tires have been set to same number on one of the digital gauges.

    ReplyDelete
  3. How about actually giving us a brand name that you reviewed?????????????

    ReplyDelete
  4. Have you noticed if any of the available TPMS systems' loss-per-unit-of-time alert ("Early Warning") is adjustable such that it would be so sensitive as to actually be superior to the temperature compensation feature? Or are they incapable of detecting a very slow leak?

    With the temperature compensation feature I would have to personally monitor the loss of pressure while driving and decide whether the rate of loss warranted a stop, whereas with the loss-per-unit-of-time alert, if it can be set to detect a very minor leak, I could just set it as sensitive as I pleased and then just let it alert me if the rate of loss exceeded my comfort level.

    ReplyDelete
  5. I did some research on this “loss-per-unit-of-time alert”, and found this info regarding this feature (I’m just reporting what the user manuals said…correct me if I’m wrong about any of this):

    TST TM-507RV: Only offers >6psi/<12 sec = >30psi/minute “Fast Leakage” alert

    Doran 360RV: Only offers >2.8psi/<12 sec = >14psi/minute “Fast Leakage” alert

    EEZ RV PRODUCTS EezTire T515/SP: Only offers >7.25psi/minute “Fast Leakage” alert

    HawksHead Talon 22: Only offers unspecified >?psi/minute “Fast Leakage” alert

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    TireMinder TM66: Offers >3psi/<2min = >1.5psi/minute “Rapid Air Loss” alert, and
    >6psi/2-10min = >0.6psi/minute “Semi Rapid Air Loss” alert

    TireTraker TT400C: Offers >3psi/<2min = >1.5psi/minute “Rapid Pressure Leak” alert, and
    >6psi/2-10min = >0.6psi/minute “Quick Pressure Leak” alert

    HawksHead Pressure Track HD: Offers >4psi/<2min = >2psi/minute “Rapid Leakage” alert, and >3psi/2-10min = >0.3psi/minute “Slow Leakage” alert

    ------------------------------------------------------------------------------------------

    Tire-SafeGuard: Only offers >3psi/2-10min = >0.3psi/minute “Slow Air Leak” alert

    ReplyDelete

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