Winter tire pressures

Discussion in 'Gen 5 Prius Main Forum' started by Paul Gregory, Nov 9, 2025 at 12:17 PM.

  1. Paul Gregory

    Paul Gregory Senior Member

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    Whenever temps drop to around freezing, my tire pressure alert light comes on. It eventually turns off after a period of driving, as the tires warm up. I prefer to add a bit more pressure, just to keep the light from coming on. Not quite such good traction, but I can manage.
     
  2. VelvetFoot

    VelvetFoot Member

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    Tire pressures drop when it gets cold. Why not turn on the gauge and look at what pressure the tires are at?
     
  3. Mendel Leisk

    Mendel Leisk MMX GEN III

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    The TPMS light supposedly don't go on until one or more of the tires drops to about 25% below the last set pressure. If you've not reset it I would suspect that set pressure would have been set at the factory, per the door jamb decal, maybe the higher value, if there's two (front vs rear). Periodic check with a pressure gauge will catch pressure drops sooner.

    Fifth gen can display the pressures? That's good.
     
  4. Paul Gregory

    Paul Gregory Senior Member

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    They either show a few psi below normal, or they say "adjust tire pressure."
     
  5. ChapmanF

    ChapmanF Senior Member

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    The TPMS is able to have a different alert threshold for each transmitter, so they could be programmed from the factory for both the front and rear placard pressures. (Of course, the first tire rotation messes that up unless you then reset the thresholds, because they're remembered per transmitter, not per position on the car.)

    Personally, I dislike how low the default alert thresholds are. You don't get to set them directly: you air the tires to the pressure you want, and use the SET button, and alert thresholds get set at some % below the current reading. When SET at mid-30s (psi) pressures, the alert thresholds were ending up in the 20s.

    I want to know about low tires sooner than that, so what I've ended up doing is just airing the tires to the max sidewall number, pressing SET, and then letting them back down to the pressures I want.

    That leaves the alert thresholds set just a few psi below my preferred pressures. Which is what I want.

    Though it does mean I can't help noticing the way pressure changes with temperature, as my light will come on with any modest cold snap, until I add some air as needed.

    One thing I don't religiously do is check for higher pressures than I prefer when the weather warms up. The TPMS doesn't offer high-alert thresholds (unless that's new in later generations than mine). So I just usually end up driving on harder tires for a while if the weather has recently warmed a lot.
     
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  6. VelvetFoot

    VelvetFoot Member

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    upload_2025-11-9_13-5-35.png
     
    #6 VelvetFoot, Nov 9, 2025 at 1:04 PM
    Last edited: Nov 9, 2025 at 1:19 PM
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  7. PriusCamper

    PriusCamper Senior Member

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    You tire pressure is too low.
     
  8. bisco

    bisco cookie crumbler

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    what is more important, cold pressure or after you've been driving a bit?
     
  9. VelvetFoot

    VelvetFoot Member

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    In other news...how 'bout those miles on my first tank? :)
     
  10. bisco

    bisco cookie crumbler

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    nice, i used to get 60mpg in my '04!
     
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  11. fuzzy1

    fuzzy1 Senior Member

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    The tire labeling and door placard figures are all referenced back to cold pressure.
     
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  12. ChapmanF

    ChapmanF Senior Member

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    The pressures on the placard are cold pressures. Pressures after driving will be higher; that's taken into account when deciding what the cold pressures on the placard should be.
     
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  13. bisco

    bisco cookie crumbler

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  14. Paul Gregory

    Paul Gregory Senior Member

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    Mine comes on long before a 25% loss of tire pressure.
    Seems more like 10%.
     
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  15. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Could be gen 5 revision. Interesting too, that it now displays all four tire pressures, much more informative.
     
  16. bisco

    bisco cookie crumbler

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    i start mine high. haven'r touched them in 2 years, and they are still at door sticker recs
     
  17. Mendel Leisk

    Mendel Leisk MMX GEN III

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    If you air up at a gas station with warmed up tires, good ploy is to put about 4 extra psi in, check and bleed them off as needed later, when cold.
     
  18. VelvetFoot

    VelvetFoot Member

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    On your first tank? :)
     
  19. bisco

    bisco cookie crumbler

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    oh ya, that thing was a beast from the get go. but i drive like my granny, have since i survived teen age years
     
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  20. VelvetFoot

    VelvetFoot Member

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    I probably have to learn some Hybrid techniques, lol.
     
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