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Tire Pressure from Dealer @ 50 Lbs ????

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by ATHiker, Feb 20, 2016.

  1. ATHiker

    ATHiker Senior Member

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    Let me start off by saying that as someone who lives in New England and listens to sports talk radio many hours a week, I know a little bit about the ideal gas law.

    Temperatures around here have fluctuated wildly. It is possible that when the dealer prepped my car it was around 25 degrees F, and when I checked my 17" tires for the first time today it was 60 degrees F.

    Even so, I was shocked.

    The pressure reading on my "good" pressure gage was almost exactly 50 lbs on all 4 tires. I checked one tire with a cheap pen gage as a double check and that read 50 lbs as well.

    Pressures listed on the door jam are 33 and 32 lbs. What the heck is going on?

    I am going to take a deep breath and wait for some of you guys to chime in befor letting air out of the tires and making an nice person out our myself at the dealership.

    Any words of wisdom?

    image.jpeg image.jpeg


    .
     
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  2. Mendel Leisk

    Mendel Leisk Senior Member

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    They screwed up: cars come from the factory with tires at max sidewall pressure, to avoid flat spotting in protracted transit/storage. Dealer is supposed to drop the pressure during Pre-Delivery-Inspection, and you pay big bucks for this. I'd check the temp spare pressure too, if you've got a spare, or maybe your level doesn't?

    There's likely a couple of oblong underbody holes that should have gotten rubber plugs at the dealership, if it's like third gen. They put strong point pins in the holes during shipping, to keep the car stable. The dealership is supposed to pop rubber gaskets into those. They're likely near the rear wheel wells, just a bit forward, and inboard of the rocker panels.

    Let 'em know on any feedback card you get.
     
  3. wjtracy

    wjtracy Senior Member

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    Ideal gas law says (520/485) x (33+15) - 15 = 36.6 psig at 60F if filled to 33 psia @25F

    (or rule-of-thumb 1 psig per 10 deg F works fine)
     
  4. ATHiker

    ATHiker Senior Member

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    Thanks for the reply.

    I found the plug properly installed (I think, photo below).

    Since only "sales professionals" will be around tomorrow, I am inclined to let air out myself and moving on --rather Going in another direction :).

    That said, I have never had tires with pressure sensors before. Do they come into play? I would belting out 40% of the air!

    image.jpeg
     
  5. Blizzard_Persona

    Blizzard_Persona Senior Member

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    Well..... You'll get better mpg...:D
     
  6. wjtracy

    wjtracy Senior Member

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    I think the TPMS comes on ~25% under design (~25 psig) so presumably you will not set those off.
     
  7. FuelMiser

    FuelMiser Senior Member

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    So, after you adjust the tire pressure, you might just want to see if the Tire Pressure Warning Symbol comes on the dash, just to convince yourself that the system is working. But it all depends on where the system was set initially. The proper procedure for any adjustment to tire pressure is to reset the TPMS by pressing and holding the button under the steering wheel until the TPMS light on the dash blinks THREE times. It should be the only button under the steering wheel, but may be difficult to locate. Obviously, the car has to be in READY mode and PARK when you press the TPMS button.

    PS: I just realized this is the Gen 4 section, so hopefully my description of the TPMS button is not too far off--what I said is for the Gen 3 cars. Sorry.
     
  8. Lucifer

    Lucifer Senior Member

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    Wait, had you driven your car before the 50pounds reading, is your gauge accurate, were the tires in the sun, is it an echo, which comes with more the the standard 36pounds, ignore the pressure on the door, toyota airs them to 36 now, but any mechanic "technician" can make a mistake, any time, any where.
     
  9. ATHiker

    ATHiker Senior Member

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    I got the gage from NPR's Car Talk site special for this car so it must be right :).

    But that was the first thing I thought, so I double checked with a pen gage and got the same reading.

    I drove about 50 miles today, and checked the tire an hour or so after I came home. I will check again tomorrow befor driving and also use the gages on my wife's 2010. Right now I am confident in thier reading.

    Car is a 4 Touring with the low profile 17" tires.
     
  10. AKCoffee

    AKCoffee Junior Member

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    50 is a good start ... Try going up by 4 psi until the ride gets too harsh or your tire dash lights come on.

    In Minnesota

    Civic Hybrid: 58 to 60 summer ... 54 winter.
    (Tires are lasting over 80k miles - 163k on the odometer I've purchased 6 tires, 7 and 8 will come in October).

    Prius v (wife's car) 50 summer 45 winter.
     
  11. rifis

    rifis Junior Member

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    Very droll!
     
  12. Mendel Leisk

    Mendel Leisk Senior Member

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    This is third gen location for the locking pin hole. It's in heavy gauge metal, inboard of the plastic rocker panels with their fasteners. That rear drivers-side wheel in the pic:

    Capture.JPG

    If you lower tire pressures yourself, you should reset the tpms threshold, it should be in the Owner's Manual how to do that. There's a button under the dash typically.
     
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  13. Lucifer

    Lucifer Senior Member

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    Ah, the tires were at least four pound high because of road heat, and get an accurate gauge, not a friction device.
     
  14. ATHiker

    ATHiker Senior Member

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    Agreed that a good gauge is in order.

    The Car Talk Guy(s) were rather effusive in their praise for the one I used first:

    Car Talk Analog Dial Tire Gauge – NPR Shop

    But certainly ther are better, and I could have a defective one.

    That said, the measurements were very close to the pencil Guage I used to double check. The pencil gauge has always been close to the reading on gas station pumps.

    The delta from standard is 17 or 18 lbs.
     
  15. ATHiker

    ATHiker Senior Member

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    Thanks for the picture -- it helped.

    I did find the locking pin hole and it had the rubbery gasket. After your report, I had visions of my rusty 1973 mustang that collected salt in nooks and crannies, so I was relieved that he plug was not forgotten.

    image.jpeg

    I tried the 2 pressure gauges again and they both registered 49 Lbs on my car, and 35 on my wife's 2010 (as expected). At this point a simple correction.

    Thanks to all.
     
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  16. KennyGS

    KennyGS Senior Member

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    I've learned to anticipate disappointment from the dealership.
     
  17. Blizzard_Persona

    Blizzard_Persona Senior Member

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    Hyper milers run the Psi at max.....
     
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  18. Mendel Leisk

    Mendel Leisk Senior Member

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    But 50 psi with the 17" is for masochists. :ROFLMAO:
     
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  19. Grus

    Grus Member

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    Yes, and there should be a Pre-Delivery-Inspection checklist or report, every dealer should have each item on the list done one by one.
    I would check the list again myself.
     
  20. ericbecky

    ericbecky Hybrid Battery Hero

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    For the most part air pressure in tires is a personal preference
    I have plenty of customers who would love to have their dealership put their tires at 50psi.

    Why do you feel the need to lower the pressure?
    Other than the number on the gauge, we're you in some way unhappy with the ride or the fuel economy at 50psi?

    It is much more dangerous to have then under inflated than over inflated.

    The tire manufacturers build in a very large safety margin when putting max sidewall numbers in the tire. Not just a few psi. Think 2x, 3x, 4x, more than your current pressure.

    .
     
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