Filling tires with air - how much per year?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by wjtracy, Mar 28, 2013.

  1. wjtracy

    wjtracy Senior Member

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    Last nite I upped our Prii tire pressures from 32 to 40. Seems like I do this at least 4 times a year. Anyone keep records how many psi per year it takes to keep the tires at 40?

    One article in Popular Mechanics said up to 12-psi per year normal leakage rate, I am thinking maybe 20-30 psi/yr is not uncommon. I am just talking the normal decay by gas permeation through the walls.
     
    #1 wjtracy, Mar 28, 2013
  2. jdenenberg

    jdenenberg EE Professor

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    Besides some leakage, the tire PSI falls in cold weather and rises as temperatures increase. Since you should rotate tires periodically and the front tires should have slightly higher PSI (by 2 PSI) than the rear to compensate for Prius weight distribution (heavier in the front), you will need to adjust PSI about twice a year anyways.

    JeffD
     
    #2 jdenenberg, Mar 28, 2013
  3. wjtracy

    wjtracy Senior Member

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    Thanks Jeff that should help me remember which tires are 2 psi higher (front).
    Well I use the Richard Schumacher tire rotation technique. I don't.
    So my front tires are newer, and I figure all 4 replaced next time.
    Cold weather I know as PV=nRT. That's about 2% Psia per 10 deg F.
     
    #3 wjtracy, Mar 28, 2013
  4. archae86

    archae86 Member

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    I try to check my tires every month and top them up to my desired pressure. I use a portable compressor that includes a reasonably accurate gauge. Try as I might for a clean connect and disconnect, I lose a little air at each of these events, and I'm sure it is not the same each time. A systematic effect I think I notice is that as the temperature drops from month-to-month I need to add extra, then when the temperature rises in the spring I can have several months in a row where I add none.

    Unless you add air very seldom, and take good care only to do it with the tires stabilized at the same temperature as the previous time, I think it would be pretty tricky to get an accurate estimate of loss rate. I'll hazard a guess that mine is under 10 psi per year, but would not ask you to put much credence in it.
     
    #4 archae86, Mar 29, 2013
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  5. Corwyn

    Corwyn Energy Curmudgeon

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    Which would be suboptimal for those of us who live in varying climates. One should check and adjust tires at the average temperature for the period between checks.
     
    #5 Corwyn, Mar 29, 2013
  6. archae86

    archae86 Member

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    Agreed, which is a reason why few of us could really answer the question as posted with any accuracy
     
    #6 archae86, Mar 30, 2013
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