Public Service Announcement: Colder temps > check tire pressures

Discussion in 'Gen 4 Prius Fuel Economy' started by Smaug1, Oct 24, 2018.

  1. Smaug1

    Smaug1 Member

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    Now that temperatures are dropping to freezing in the northern hemisphere, check your tire pressures. The air gets denser and I've found I lose about 5 psi, which hurts fuel economy. (I keep a nice little Black & Decker inflator in the back)

    I'll check tonight before I commute home, then in late January or so when the temps have dropped close to 0°F. (-18°C)
     
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  2. bisco

    bisco cookie crumbler

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    i keep mine at 42/40. it's a bit stiff, but helps with the tpms light.
     
  3. The Professor

    The Professor Senior Member

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    Assuming you set the TPMS when the pressure is lower, then inflate them higher...
     
  4. bisco

    bisco cookie crumbler

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    never touched it from the factory
     
  5. alanclarkeau

    alanclarkeau Senior Member

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    Hmmm, not that useful - that assumes that you live in one part of the world.
     
  6. The Professor

    The Professor Senior Member

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    In which case, the TPMS will trigger whenever the pressure falls around 5PSI under what the pressure was when they were last set, which could be anything. You might want to set it to a known pressure :D
     
  7. bisco

    bisco cookie crumbler

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    it is set to a known pressure from the factory, isn't it?
     
  8. The Professor

    The Professor Senior Member

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    When the system is first initialised (or last initialised), the TPMS sets the trigger threshold to around 5 PSI below whatever the pressure sensors are reading. It could have been set at any time by anyone re-initialising it in the car's settings menu after that first ime, and it should be done if you've ever had the car serviced and the pressures have been adjusted (but many dealerships will not bother). There is no way to know if you've never done it yourself.

    My point is... as you've never done this yourself, you have no idea at all what pressure they're set to trigger at. It could be set to something sensible, but what if it's set to trigger at 1PSI or something dangerously low?

    In general, if you're comfortable with the pressure they're at now (e.g. 40 or so) just go into the settings menu and initialise the TPMS. Takes two seconds. If it drops to 35PSI it'll then warn you, and I'd imagine that'll be when you'd want to add some air anyway.
     
  9. bisco

    bisco cookie crumbler

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    whenever i check the pressures, they are in the high 30's to low 40's. i would prefer there were no tpms, but that's just me.
     
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