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SGTJOE's avatar
SGTJOE
Explorer II
Dec 07, 2019

Continental Tires PSI rising 20

I recently bought Continental 255/70R 22.5's for my Tradewinds, it has always ran Michelins but none were available. I'm traveling from Southern Utah to Southern Arizona and am running 100psi in all 6 tires. I have a TST TPMS that I've used since TST first started that monitors each tires temperature and psi. The 100psi goes up to 120psi going down the road at 65mph. Outside Temps were running high 50's/60's. The Michelins never went up this much. I don't think they ever went more then 6-8 psi, even in 108 outside temperatures. My Honda CRV tow vehicle only gains 2 to 4 psi and these are with Continentals also. My old Michelins were 14 ply and the new Continentals are 16 ply, could this be the cause???

Is there anyone on here who is running the same size Continentals with a Tire Pressure Monitor System that monitors PSI and Tire Temps?? One more thing my Tire temperatures were running a few degrees above the outside temps. The tires were not hot at all, only problem is the 20 degree rise of the psi
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  • Chum_lee's avatar
    Chum_lee
    Explorer
    Dec 07, 2019
    "Water vapor causes some deviations from the ideal behavior as at typical tire temperatures and pressures water doesn't quite respond as an ideal gas. Maybe the air you have in the tires isn't particularly dry."

    Just a guess. You might want to try bleeding the existing air from the tires and filling them again with . . . . KNOWN DRY AIR! Having filled the tires with excess humidity may be an issue. 20 psi change from cold to hot is a lot especially in winter time. I'm generally not a fan of using nitrogen in RV tires but that would be another option if dry air doesn't help.

    Edit: Do all the tire pressures rise equally? Have you checked the tire pressure with a KNOWN GOOD MECHANICAL GAUGE to confirm that your TPMS is reading correctly and that the known good gauge and the TPMS are reading consistently? In aviation you really need not one, not two, but three independent ways to confirm the accuracy of your data to be confident.

    Chum lee
  • Sam_Spade's avatar
    Sam_Spade
    Explorer
    Dec 07, 2019
    SGTJOE wrote:
    One more thing my Tire temperatures were running a few degrees above the outside temps. The tires were not hot at all, only problem is the 20 degree rise of the psi


    Those two pieces of data don't match.

    Have you actually felt the tires to see how hot they really ARE ?
    HEAT is the only thing that will increase the pressure.

    I think there is no validity to the temp readings of a TPMS.....since the sensor is not mounted on the tire itself. For tires your size, they often are at the end of a VERY long metal valve stem.

    I don't pay much attention to the actual readings on my TPMS as they aren't very accurate but seems like I remember increases similar to that in the summer time. I have "off brand" truck tires.
  • William_B's avatar
    William_B
    Explorer
    Dec 07, 2019
    Mine go up at least that much. What is the problem? They are designed to do it, and before TPMS you never knew or even thought about how much they increased.
  • DrewE's avatar
    DrewE
    Explorer II
    Dec 07, 2019
    Pressure increase is directly related to the air temperature (and the outside air pressure); it's a simple matter of physics and has nothing to do with the brand of tire. Assuming basically dry air, it very nearly obeys the ideal gas law. Water vapor causes some deviations from the ideal behavior as at typical tire temperatures and pressures water doesn't quite respond as an ideal gas. Maybe the air you have in the tires isn't particularly dry.

    If you've driven up a mountain, the increase in altitude will cause a small increase in measured tire pressure since the atmospheric pressure goes down a bit. It's not a huge difference, less than 5 psi for any road you're likely to encounter.
  • olfarmer's avatar
    olfarmer
    Explorer II
    Dec 07, 2019
    WOW, 20 psi gain
    seems too much to me at those low temperatures! I don't have an answer to your problem but good luck figuring it out! I would definitely check the tires with a reliable gauge and if the readings are correct I would call the tire company for support!
  • MountainAir05's avatar
    MountainAir05
    Explorer II
    Dec 07, 2019
    quick way to see if they in deed go that high is check cold and once they are hot, pull over and check them manual. My only go up 4 max but not your brand. They are Michelin.
  • lryrob9301's avatar
    lryrob9301
    Explorer
    Dec 07, 2019
    NO, the temperature increase you are seeing is perfectly normal. Your Michelins did the same you just don't remember. All motorhome tires will build air pressure as they run down the road some a little more than others due to tread resistance and side wall construction.

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