Tire Pressure Poll - Where is Yours?

Discussion in 'Gen 2 Prius Fuel Economy' started by bigmahma, May 19, 2007.

?
  1. 36/38

    13.7%
  2. 38/40

    12.3%
  3. 40/42

    40.7%
  4. 42/44

    14.0%
  5. 44/46

    4.7%
  6. 46/48

    1.3%
  7. Higher

    9.0%
  8. I dont' know (be honest)

    4.3%
  1. bigmahma

    bigmahma New Member

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    I have mine up to 40/42 - but i'm hearing others go even more!

    Where is that 'sweet spot' for milage and handling?


    *edit*

    Yes the numbers are reversed - the first number is the BACK TIRE - the last number is the FRONT TIRE.

    Thanks!
     
  2. seasalsa

    seasalsa Active Member

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    Mine are 42/40, I think you have the front/rear reversed.
     
  3. jeremyandmelissa

    jeremyandmelissa New Member

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    I have mine at 42/42 is there a benefit to having the front or rear tires more inflated than the others?

    And is it written 42 (front)/42 (rear) or the other way around?

    Over-inflating probably cuts down on friction, but it must certainly also be more dangerous in terms of handling and emergencies right?
     
  4. seasalsa

    seasalsa Active Member

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    Factory recomendation due to more weight on front.

    Common practice on this site at least is F/R

    Depends on how you define over-inflation. There is a max inflation pressure listed on the tire. 42/40 does not exceed the max pressure for the tire and is not dangerous.
     
  5. priussoris

    priussoris New Member

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    ours are 40/38 we average 52-53 mpg combined city /hwy driving
     
  6. Rangerdavid

    Rangerdavid Senior Member

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    Yep, front should be 2 lbs. more than rear. Mine are also 42-40. I'm averaging 53 mpg.
     
  7. Darken

    Darken Active Member

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    Didn't want to go as high as 42/40 so mine sit at 40/38. Current tank is 60.1 MPG (558 miles)
     
  8. alexstarfire

    alexstarfire New Member

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    42/40 give or take, whether keeps changing a lot around here, and I'm sitting at 64.0 MPG with a little over 400 miles on the tank.I'd say that isn't too bad. I'd rather have my tires pumped up a little more, but I'm worried about going over the sidewall pressure ratings.
     
  9. tripp

    tripp Which it's a 'ybrid, ain't it?

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    42/40 for me. I started out at 40/38. I'm getting 51.1 MPG with a 5 mi one way commute over hilly terrain.
     
  10. Neicy

    Neicy Member

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    Just increased mine from 35/33 to 40/38 today. Hope to see a mileage improvement soon.
     
  11. Mary Snyder

    Mary Snyder New Member

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    Mary</span>

    <span style="font-family:Arial">
     
  12. nerfer

    nerfer A young senior member

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    <div class='quotetop'>QUOTE(bigmahma @ May 19 2007, 09:24 PM) [snapback]445931[/snapback]</div>
    You should've had two more options: "factory setting of 35/33", and "no idea/haven't checked".
     
  13. nerfer

    nerfer A young senior member

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    <div class='quotetop'>QUOTE(Masnyd @ May 20 2007, 03:49 PM) [snapback]446249[/snapback]</div>
    Gas stations may do this, particularly full-service ones if you live in a state that has those, but it's better to buy a $2 or $3 tire pressure gauge and then you can do it yourself whenever needed - pencil type gauge is fine, the round ones work well also, probably easier to read but can only be read while it's on the tire. You just unscrew the cap on the air filler nozzle (the black pencil-shaped thing sticking out about 1.5" from the tire, near the hubcap), and put the gauge on the end. Often the dealership or oil-change places leave the tire pressures low (gives a softer ride, but lowers the mpg and the life of the tire, if it's more than 10 psi low you risk having a blowout while driving). I've checked the tires after having them rotated, and the dealership didn't change the pressure, so now the tires were in the back had higher pressure than the ones in front.

    The tire pressure warning indicator you mention is only for the very low psi conditions where you risk imminent blowout of the tire. It won't tell you if you're just a little bit low and losing maybe 5-10% of your mpg. Of course, the people this poll is apparently targeted at are over-pressurizing the tires. The placard on the frame inside the driver's door recommends 35 psi for the front tires and 33 psi for the rear tires. However, the tires themselves are rated to safely operate up to 44 psi, so many Prius owners take advantage of that and pick some intermediate value. It does change the handling a bit, but the tires last longer and give better mpg.
     
  14. HTMLSpinnr

    HTMLSpinnr Moderator
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    When I had the OEM Integrity tires on the car, I ran 42/40. I tried that w/ the then new Allegras and they were WAY too squirrely on the freeway going over bumps/corners. I dropped to 40/38 and handling improved significantly.

    Nice thing about the Allegras is that they seem to hold pressure much longer than the Integritys did.
     
  15. brad34695

    brad34695 New Member

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    Wow! I can't believe this topic came up, becuase I was going to initiate a question regarding tire pressure. I bought an '07 two months ago. Being "old school" I thought 32 lbs for all four tires would be sufficent. When I checked my tire presuure last week, I made sure I had 36 lbs for all four tires and saw my MPG increase from 50 MPG to 54 MPG. I did not know that 2 lbs tire pressure difference between front and back is benefical.

    My Prius came with Goodyear P185/65R15 tires. The sidewall says I can fill them up to 44 lbs max tire pressure. Would everyone advise I go to 44/42 lbs? I live in Florida, and with summer approaching it will consistantly get 90 degrees here everyday. I don't want to be driving 70MPH on the interstate and cause a blow out. Any sugguestions??? Lastly, is it two lbs more in the front tires or back? Thanks in advance!

    Brad
    Tampa Bay Florida


    <div class='quotetop'>QUOTE(bigmahma @ May 19 2007, 09:24 PM) [snapback]445931[/snapback]</div>
     
  16. JimN

    JimN Let the games begin!

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    <div class='quotetop'>QUOTE(brad34695 @ May 20 2007, 04:42 PM) [snapback]446271[/snapback]</div>
    Brad, yes the front tires are generally inflated 2 psi more but I haven't noticed a difference. I'm running 45/45 now and have noticed the ABS kick in for a second or so when braking on dry pavement a few times. This did not happen at 42/40.
     
  17. brad34695

    brad34695 New Member

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    Jim,

    Thanks for the quick reply and the advice. One last question. How cold does it need to be to block your front grills? Living in Florida, I don't know if I can often take advantage of that, as the high tempeture rarely gets below 50 degrees here in the winter time. Evenings can get in the 30's and 40's, so maybe I could block the grills during winter night driving. Again thanks for the tire pressure sugguestion.

    Brad
    Tampa Bay Florida

    <div class='quotetop'>QUOTE(JimN @ May 20 2007, 05:17 PM) [snapback]446284[/snapback]</div>
     
  18. nerfer

    nerfer A young senior member

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    <div class='quotetop'>QUOTE(brad34695 @ May 20 2007, 04:42 PM) [snapback]446271[/snapback]</div>
    Being underinflated while driving high speeds in hot temperatures is the surest way to a blow-out (remember the infamous Ford Explorer/Goodyear recall?). Underinflation and high speeds independently cause the tire to heat up, add in hot temperatures and they can overheat. That said, I'm not sure if going to extra-high psi will help the heat issue or not, there's probably a point of maximum safety. As JimN and htmlspinner imply, there are other handling issues with extra-high psi. I keep it about 39-37 myself, somewhere middle-of-the-road.

    It's 2 more psi in front compared to back, when in the mid-30's psi. Whether that difference needs to be preserved (absolute difference), increased (percentage difference) or decreased (doesn't affect anything) at higher psi has not been scientifically validated, AFAIK.
     
  19. Mary Snyder

    Mary Snyder New Member

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    <div class='quotetop'>QUOTE(nerfer @ May 20 2007, 05:26 PM) [snapback]446261[/snapback]</div>


    Thanks Nerfer for the clear explanation and directions for filling the tires. I have copied your message and I think I will study it and learn to do it as there are hardly any full service gas stations in Florida any more. The one thing I don't understand though is in the manual it says to reset the pressure warning indicator after you fill the tires. Do you not do this, or do you mean you don't have to?.

    Sincerely,

    Mary
     
  20. Graz

    Graz Member

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    Hey Everyone,

    Long time no post. As you can see from my sig, I use a higher pressure than any of you have admitted. I replaced the OEM Integrities, with a set that "supposedly" can handle much higher pressures. However... At the MAX pressure, these tires wander all over the freeway, and feel unstable at higher speeds. I do now average 48.5 MPG per tank on my daily commutes. I believe that this is a worthy reason to inflate the tires higher than the door plate recommends. I can tellyou though that th ride is noticeably harder and there are now more little squeeks in the interior. Probably because the car isn't put together strong enough to handle this kind of vibration.

    YMMV
     
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