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Tire Pressure Q's

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by acadiaphile, Mar 17, 2008.

  1. acadiaphile

    acadiaphile Junior Member

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    I came to Prius Chat with one question which I tried to answer by searching the forums. In doing so, I ended up with my initial question unanswered and another one to add:rolleyes::
    1. I've been losing tire pressure intermittently on random tires for several months. After testing various hypotheses, I ended up presuming that it was teens in the neighborhood letting a bit of air our for whatever amusement this offers. But this past weekend, we went on a trip (~200 mi. away) and the tire pressure light went on the morning after we arrived. So presumably something else is going on. Any ideas?
    2. What's up with the tire pressure recommendations anyway? The car says it should be 35/33. The tires themselves indicate higher PSI. And it looks like some PC folks are going considerably higher. What're the risks? (I presume the primary benefit is improve MPG due to decreased resistance.)

    TIA for your help! My family and I are headed for another (~1,000 mi.) road trip in a few days and I'd love to see what I can do to remedy the situation (and improving MPG's always nice, too!).

    Cheers,
     
    #1 acadiaphile, Mar 17, 2008
  2. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    I did have a slow leak for a while in one of my tires. But you said intermittent and multiple tires, so I'd stick with the kids hypothesis. At least for now.

    Any chance it was cold in the morning when you get in the car? Cold air causes air to shrink which causes the tires to drop in pressure which causes (you guessed it) the sensor to go off. Just a thought.

    Over-inflating is not recommended by tire manufacturers, dealers, or anyone in an authoritative position. The tires are considered to be part of the suspension of the car and when you over-inflate them, your ride becomes stiffer. Having said that, everyone that I'm aware of who has over-inflated their tires has seen an immediate improvement in their mileage. I'm currently running at 55f/53r and averaging 61.7 in 37ºF. I also have my grill fully blocked but I know that the tires are contributing a major portion to that mileage.

    If you are concerned but want to test it, I suggest that you go up to 45f/43r and drive around with that for a week. Compare your mileage. For the test to be fair, it has to be normal driving conditions.
     
    #2 TonyPSchaefer, Mar 17, 2008
  3. sandsw

    sandsw Member

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    Most definitely not your problem and this story is probably apocryphal anyway.

    It had been a sweltering summer and the tyres on the car kept going flat. The owner thought it might have been a teen thing, so a stake-out was made.

    About 10:30am, a cockatoo flew down to the birdbath, after getting nice and wet, it then made its' way over to the vehicle, took off the tyre-cap and stuck its' beak down into the valve - thus releasing a steady flow of air. Once that tyre was exhausted, the cocky moved onto the next tyre.

    Cheers.
     
    #3 sandsw, Mar 17, 2008
  4. bbald123

    bbald123 Thermodynamics Law Enforcement

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    This week I found that ALL of my valve cores were loose from the factory. Three were 1/4 turn from tight and one (and it was leaking) was 1/2 turn from tight. Might be worth a check.
     
    #4 bbald123, Mar 18, 2008
  5. acadiaphile

    acadiaphile Junior Member

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    Thanks for the responses. As far as the valve caps--they've been disappearing--thus furthering the "deviant yoot" hypotheses.

    Regarding the bird story--very funny, although I'm reluctant to believe it's true. Nevertheless, the following story is true:

    Several years ago my DH (then boyfriend) and I drove with my dog (a 25 lb. mutt) to visit my friends who have numerous animals (3 very large dogs, 2 horses, 2 goats, fish, and an African Grey Parrot).

    We arrived around 3 am and stumbled into my friend's new home for the first time. In the kitchen was a very large, refrigerator-sized cage which was home for the parrot. My dog, Siri, is a city dog. As such, what she's seen of birds is limited primarily to pigeons and sparrows. When she saw and sniffed the cage she trotted over to it and stared with considerable curiosity.

    The parrot, upon seeing Siri, hopped off her perch and sidled over to Siri. She cocked her head, looked at Siri, opened her beak and said, "Hello, little dog!" Siri's response was something a kin to::eek: Never, before or since, have I seen a dog whose expression was so like that of a cartoon character.

    Meanwhile, I'm thinking of swabbing the valve covers with Vaseline as a benign yoot deterrent.
     
    #5 acadiaphile, Mar 18, 2008
  6. barbaram

    barbaram Active Member

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    I've noticed there can be a big variance in tire pressures. You don't say where you are.... even sitting in the sun, one tire may show higher than the others. Potholes are notorious for stealing air from tires, so if you have rough roads they may be to blame.
    As for inflation, check the mfg recommended limits. Go to the higher side, but as stated by others here, not over.
     
    #6 barbaram, Mar 21, 2008
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