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ezgoin's avatar
ezgoin
Explorer
Jun 24, 2017

"Cold" tire pressure question

During the Arizona summer my cold tire pressure reads about 5 lbs ABOVE my normal 85 lb desired cold pressure before driving. Should I let 5 lbs of pressure out before hitting the road in extreme heat? If I do, will I be under inflated when I arrive at a cooler location?
  • Old-Biscuit wrote:
    See what I mean.......:B

    Not racing just RVng.

    Don't make it complicated cause it isn't


    Travel day...
    Check psi ---adjust up/down....drive

    Next travel day----repeat

    I also could have written , 'no problem , but my answer explaines
    why.
  • Tire mfgrs. state cold means before you start driving no matter what the outside temps are.
  • See what I mean.......:B

    Not racing just RVng.

    Don't make it complicated cause it isn't


    Travel day...
    Check psi ---adjust up/down....drive

    Next travel day----repeat
  • Adviced cold pressure is calculated by the vehicle maker for 65degr F /18 degr C.
    Then the warming up of rubber of tire is in balance with cooling down of that rubber so the rubber wont go above a sertain temp at wich its hardens and so damages in next bendings of it by the deflection of tire. This is the goal of all pressure calculation.

    When its warmer outside the temperature differences are smaller but also the higher pressure inside gives lesser deflection so lesser heatproduction. And the other way around when its colder outside.

    My estimation is that if you take car of advice pressure calculated back to 65 deg F , the tires wont overheat in a temperature range up to 110 degr F .

    So at higher ambiënt temp you need higher pressure.

    Will give tabel for that .
    Use it like this.
    Look up the determined advice pressure in the line with 65 degr F , is fatt printed. Then go in that row to the ambiënt temperature you measure the pressure cold ( when inside tire temp= outside tire temp, that simple) Then see what you have to fill or have to measure to be save for the tires.

    So for example , if advice pressure is 70 psi , and you measure a cold pressure of 76 psi at an ambiënt temp of 100 degr F , dont blead air from the tire to bring it to 70 psi, it needs that 76 to give it lesser deflection so lesser heatproduction , because temperature differences between rubber and surounding air is also smaller so lesser cooling down .
  • time2roll wrote:
    "Cold" is relative. Set the pressure in the morning before you roll and before the sun hits the tires. Adjust up or down as needed. If you have moved to a different climate then repeat the procedure the next morning.


    There you go....nice clear concise simple answer.

    :B
  • "Cold" is relative. Set the pressure in the morning before you roll and before the sun hits the tires. Adjust up or down as needed. If you have moved to a different climate then repeat the procedure the next morning.
  • Only if you will be in the "extreme heat" for more than a couple of days.
    Starting out at 5 over is fine for a day or two.

    After all, some folks insist on using the max. pressure on the sidewall and in some cases that is 15-20 PSI over what would be optimal.