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I've seen cold tire pressures listed...what about warm?

Discussion in 'Prius v Fuel Economy' started by Paranormal Rob, Jul 22, 2017.

  1. Paranormal Rob

    Paranormal Rob Active Member

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    I've seen many cold psi at 42/40, 40/38 but does anyone use a wireless TPMS that shows what the pressures are after they are warm?

    I got this wireless TPMS weeks ago and so far its awesome. So I was wondering if anyone else was monitoring live pressures/temps. I can also set alerts as well, so if there's an upper psi/temp I should set, feel free to chime in.

    CACAGOO TPMS Tire Pressure Monitoring System with Real-time Warning, LCD Display, 4 External Tire Pressure Sensors, Psi/Bar, °C / °F Units Selection


    Posted via the PriusChat mobile app.
     
    #1 Paranormal Rob, Jul 22, 2017
  2. Paranormal Rob

    Paranormal Rob Active Member

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    https://www.amazon.com/gp/your-account/order-history/item/ref=oh_aui_i_d_old_o20?ie=UTF8&itemId=jlmhkqhmlqpnwn&orderId=111-1482157-5005802&returnSummaryId=&shipmentId=DMqtv07l4

    Posted via the PriusChat mobile app.
     
    #2 Paranormal Rob, Jul 22, 2017
  3. Sam Spade

    Sam Spade Senior Member

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    Yes. And regardless of the vehicle in question, the pressure when warm or hot is NOT significant.....because it varies too much.
    The only time you should worry about that at all is if 3 tires come up to a certain pressure and the 4th is WAY off.
    Even than that probably means one of the sensors is bad.
     
    #3 Sam Spade, Jul 22, 2017
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  4. Paranormal Rob

    Paranormal Rob Active Member

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    Thanks.

    I suppose 42/40 or 40/38 after sitting all night, watch what happens and adjust the alert threshholds some above that.


    Posted via the PriusChat mobile app.
     
    #4 Paranormal Rob, Jul 22, 2017
  5. mikefocke

    mikefocke Prius v Three 2012, Avalon 2011

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    People racing cars regularly monitor the heat of the tire tread. They use the results to adjust the pressure in the next set of tires they use.

    When I was running max-traction tire pressures on wide low profile tires, I'd feel the tire when I stopped after a long run in hot weather. I even bought a heat sensing laser guided hand held "gun" (~$30) just to get my hand sensing in synch with what the numbers wich would be displayed. Though in truth I've used it more to adjust the home HVAC than I ever did on tires.
     
    #5 mikefocke, Jul 22, 2017
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  6. Sam Spade

    Sam Spade Senior Member

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    If you have a good monitoring system, the default thresholds should be fine if you set the starting pressure properly.
     
    #6 Sam Spade, Jul 23, 2017
  7. Paranormal Rob

    Paranormal Rob Active Member

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    Weigh stations use technology to see tire heat on trucks as they drive thru. Easier, quicker, safer. If they see on with too much heat as compared to others, they stop the truck

    Posted via the PriusChat mobile app.
     
    #7 Paranormal Rob, Jul 23, 2017
  8. Paranormal Rob

    Paranormal Rob Active Member

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    #8 Paranormal Rob, Jul 23, 2017
  9. Kenny94945

    Kenny94945 Active Member

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    I don't use a wireless...yet why not?
    (My other cars show individual pressures on a dash screen.)

    The "old rule of thumb" is hot tire pressure should be 10% higher than cold tire pressure.
    In this case:
    Running 42 cold should be about 46-47 hot
    Running 38 cold should be about 41-42 hot

    The true way is with a pyrometer.
    One first needs to know the manufactures tire temp operating range....sometimes difficult to obtain.
    Then once the tires are "good and hot", quickly check the temp with the pyro.
    Adjust pressure to fall with the operating temp.
    A pryo can also help indicate if alignment modifications are needed.
    That's the quick basics.

    Race setup, comfort, wear, handling feel are some other aspects, yet I believe in a Prius owner street driving case we are desiring longevity and notification of a tire losing air pressure.

    Have fun.
     
    #9 Kenny94945, Jul 24, 2017
  10. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Why not stick to cold pressures? Not as much fun?
     
    #10 Mendel Leisk, Jul 24, 2017
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  11. Paranormal Rob

    Paranormal Rob Active Member

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    Nahhh, I just wanted to see what heated tire psi should be so I can set alerts on my aftermarket wireless TPMS.

    Cold at 42/39 looks to be 46/44.

    Whats odd is when I try 42/40 front will go 39 or 41. For some reason I can't get it at 40, but since they are 46/44 heated, I'm not going to worry about it.

    Posted via the PriusChat mobile app.
     
    #11 Paranormal Rob, Jul 26, 2017
  12. Paranormal Rob

    Paranormal Rob Active Member

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    #12 Paranormal Rob, Jul 26, 2017
  13. fuzzy1

    fuzzy1 Senior Member

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    Agreed. I have understood that as long as the cold pressures meet recommendations (for us regular consumers, not the racers), the hot side will be just fine, and safe.

    And that 'max pressure' listed on the sidewall is supposed to be a cold pressure, not a warmed running pressure.
     
    #13 fuzzy1, Jul 26, 2017
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