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Monday, June 27, 2016

Quick TPMS test and a couple of tips.

As the use of TPMS in the RV world continues to spread, I am noticing a number of comments on usage, pressure and temperature accuracy and general reliability of different systems.

I am in the process of making a test fixture to allow calibration check of pressure and possibly of temperature reporting also. I hope to have the first round of testing in a few weeks. I have a target of offering a "TPMS Pressure Test" in August in West Springfield at the FMCA Reunion for folks to learn the actual accuracy of their individual system. I will collect and report the findings in Sept.

As I do some initial runs, I am noting some interesting results and readings that need additional investigation as I am not always seeing numbers that I am expecting. This is especially true when it comes to temperature readings.

One thing I have learned is that it might be a good idea for everyone to do one test on their own unit.

With all tires properly inflated you can confirm that your system can provide a quick response and that your monitor is receiving the radio signal properly. With someone watching the monitor, go and quickly unscrew the sensor and have the person watching the monitor beep the horn as soon as the sensor issues its warning. Hopefully you will see that your system consistently reports the loss of pressure the sensor is seeing in one or two seconds.

Be sure to securely re-attach the sensor and maybe even give it a little squirt of soapy water or even Windex to check for leaks. I certainly do not want anyone reporting back that they had a tire failure because they lost air due to a loose sensor.

A side note. My sensors, and I believe many others do, have an "O" ring seal around the battery chamber. As with any device containing a battery that is exposed to water, I give the battery chamber a little squirt of WD-40 to help prevent corrosion of electrical components. You might take this opportunity to also inspect the "O" ring for tears or cracks. Don't forget this little rubber piece ages just as rubber tires do. I keep a couple spare "O" rings on hand just in case. Your TPMS supplier should have a package of replacements for a nominal fee or you can pick up some at your next RV convention or show.

 If you have a monitor that is small and portable, I suggest you not carry it around with you as one of the features we want to test is the ability of the monitor to receive the signal over the distance from the tire to the location you have mounted the monitor. This would especially be important for those monitoring sensors on a toad. You don't have to actually hook up the toad but at least park it in an appropriate location and distance behind the RV.

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  1. The best tip is to NEVER use these on rubber valve stems. We learned the hard way. The sensors weigh 13 grams and the centrifugal force will deform the base, eventually causing catastrophic failure. If you contact them or read their brochures, purveyors of these devices will recommend metal stems but won't require them. Otherwise, TPMS are great.

  2. I think that the style of sensor which is completely within the tire rim will give a proper indication of tire air temperature, but how accurate are the readings from a sensor which screws onto the end of the valve stem (or even worse, onto a valve stem extender)? I would think that the stem and sensor, which are whirling around in ambient air, would be cooled by this effect and read substantially lower temperature than the hot air within the tire.

    1. Ed, While it is true that internal TPMS will give a reading (hotter than external sensors) the air inside a tire is not all the same temperature. I know this is not easy to grasp and a bit counter-intuitive but there is data on this in the industry. Personally I do not pay a lot of attention to the temperature reading as it goes up and down throughout the day depending on the Sun or if it's raining or how fast I am driving. Since I run my tires with enough inflation to give me about 15% extra load capacity over the measured actual load on the tires I seldom see more that 20 to 30F rise and more normally they run in the +10 to + 20F range. IMO pressure is the most important thing for a TPMS to monitor and report and I have confirmed my sensors read +/- 2 psi from actual based on a ISO calibrated digital gauge.

  3. Some of our tips based on observations of a couple different TPMS we have used over the past 10 years.

    I bought the best digital tire gauge I can find and I inflate each tire based on 4 corner weights to the recommended pressure using the digital gauge. I then compare that pressure to what my TPMS monitor says and I write it down. Now I know what my monitor should read for each tire. In other words if my digital gauge says 100 lbs for each of 4 tires on an axle I know they are all equal. But maybe my TPMS monitor does not read exactly 100 lbs for each of those tires. Now I know what my monitor should read for each tire.

    At least once a month I take each sensor off each tire to make sure it goes to zero. I then reinstall the sensor to make sure it returns to the correct pressure. If the pressure is off I then check again with my digital gauge and adjust as needed.

    Since the technology is now available we cannot imagine going anywhere without a TPMS.

  4. Had a tire blow from fender contact and it took about 30 seconds before my monitor sounded. Was told it works best for slow leaks or gradual loss of pressure. Wish I had known before I purchased the unit.

    1. I have tested my sensors by unscrewing one from the valve stem, and the warning is nearly instantaneous. Perhaps you should test your own sensors. I suspect that the sensors, receiver and code are likely created by some single Chinese company and marketed with slight variations in the case and display, leading me to suspect that they all work pretty much the same. Still, for your own confidence, you should test how your system actually works.

    2. RE "tire blow". Without a picture or more information I might think you did not have a run low flex failure but a tread separation. I suggest you review my post of April 12, 2016 to learn more. TPMS warn of air loss. Have you tested the response time of your sensors as mentioned by Ed Price?

  5. We are full-timers, with a 43' sierra 5th wheel travelling allover North America. I've been using the Tire Tacker TPMS for 2 years and in my opinion they are worthwhile. them installed the 4 RV wheels, as as on all 6 wheels on my F350 tow vehicle. Prior to leaving an RV park in the morning, I remove all 4 TPMS' on the RV to reboot them. Takes 30 seconds. Doing this I know the monitor cab has fresh data and good to go. The PMS's on the truck are constantly up to date as this is our transportation once we drop anchor. Of course I check the tire pressures the night before a travel day to verify pressures.

    I've had a low pressure warning on one of the dualies on the truck - lst stage of tread separation - bad tire. I've also had a low pressure warning due to a bad valve stem. I now run stainless steel valve stems all around.

    Also, I got tired of using cheap 12v tire inflators. I went a bought a compact 120v 6 gal air compressor. Very quick to inflate the tires on my truck and RV as needed. The compressor tank shpould be sufficient if I have a low reading on the road. If necessary, I can fire up my portable 2000wn generator. Of course, now that I've got a decent portable compressor, my tire pressures rarely need topping up.

  6. I purchased Tire Minder a few years at an RV show. I have 2 friends who flipped over totaling their vehicles and trailers due to a blowout. I don't want that happening to me so I have become a tire freak. I always check my tires before a trip and on my return. I always use the tire monitor. One time it did blink red due to an air loss. I checked the pressure and indeed it went down suddenly 8 pounds. I inflated the tire with a battery powered inflator and stopped a few times on my way home. Next day I had the tire checked and the stem was bad.
    I will never take the trailer out without using a device that monitors tire pressure. I like the Tire Minder, but it is not very easy to calibrate. They have a new one out and I hope that one is more user friendly.


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