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Tire Pressure Increase

Discussion in 'Gen 2 Prius Main Forum' started by smartalec89, Apr 15, 2009.

  1. smartalec89

    smartalec89 The Official Alaskan

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    After a long time of debating whether or not I should increase the air pressure in my tires, I decided to go for it on my next fill up. I usually fill up every 280 miles and drive the exact same routes every week without much deviation. Prior to changing the pressure in my tires the best MPG I could get was 42.5 mpg for the 280 miles. At the nest fill up I drove over to the air and inflated my tires 44/f and 42/r. I decided I would see what kind of increase I could get out of the car. Well after filling up the tires I noticed a decrease in rolling resistance which made it much easier to accelerate in electric. I had expected this. What I didn't expect was a mpg improvement of so much. I went and filled up today at ~280mi as usual and I was getting 51mpg on screen and calulated. Is it typical to get this big of an improvement or do you think I changed my driving habits when I inflated the tires more? I would appreciate any comments on this.

    Thank you,
    Smartalec89
     
  2. blamy

    blamy Member

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    Thats pretty much what tire pressure will do for you. You did mean 44f and 42r right? Front tires should be two psi more than the rears. Enjoy!
     
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  3. KTPhil

    KTPhil Active Member

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    One tank isn't enough to measure the effect. Average four or five tankfuls and you can have ore confidence in the results. You will revert to yoru old driving habits by then and can get a fairer picture. Most report increases on ony a few mpg. The tires will wear more evenly with the higher pressure, too. Most wear out the outside edges long before the center.
     
  4. smartalec89

    smartalec89 The Official Alaskan

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    Yeah, oops I typed it in wrong. thanks
     
  5. smartalec89

    smartalec89 The Official Alaskan

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    I will see how it works out over the next couple of tanks. I will keep this post upto date with my mpg over time.
    Prior tanks from recent to oldest are:
    42.5, 41, 40.4, 38, 39.7, 40.1, 34, 36.3 - Avg. is 39.0mpg
    I have kept all my mpg info since the begining of this year. I purchased my 2009 package 2 in November. I do realize temp. is a factor for comparison. It is warming up so I assume I would continue to get better anyways.
     
  6. PA Prius

    PA Prius Active Member

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    Right, I'm guessing the increase in psi may have gotten you 3 or 4 mpg. Unless of course you were running very low before.

    PAP
     
  7. smartalec89

    smartalec89 The Official Alaskan

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    I would assume it was really low because I was driving with them all winter...No studs for me
     
  8. jyl

    jyl New Member

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    Also, if you measure pressure in a cool morning before tires have been driven on, then after tires have heated up by driving 70 mph in the midday heat, the pressure can be 2-4 psi higher.

    Exactly how much depends on how hot the tires get. This is what I've observed on my other car, that has a SmarTire remote pressure gauge.
     
  9. smartalec89

    smartalec89 The Official Alaskan

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    I understand that. I will check the pressure every couple of days. I don't take long trips in the car. My daily drive is about 25 miles. I would never drive 70 mph in Alaska. Since we have double fines along our highways. I think I will have to adjust the pressure as it gets warmer out. Usually we get 70-80 deg weather in the summer, but I have seen it in the 100's
     
  10. PA Prius

    PA Prius Active Member

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    Right, but don't fill your tires according to what they may become when warm. Both vehicle manufacturer suggested psi and sidewall max psi are cold psi. They are already figuring in that the psi will rise when they get warm as well as rise if you go over a 10,000' pass. Burst psi is about 4x that of the sidewall max.

    PA P
     
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  11. smartalec89

    smartalec89 The Official Alaskan

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    Sounds good to me... I guess I could just let it go then and not worry about it to much then. I just did a 64mi round trip and I averaged 49mpg the entire trip. When I did the same trip before it was only 39mpg so there is definetly some improvement over what I have had before. I will be posting some pics of my sweet 09 soon. Oh and as far as not doing any long trips I just got voluteered to do 400mi round trip next friday. I will log all my data from that trip to see what I can crank out of it. Thank you everyone for the advice.
     
  12. ETP

    ETP 2021 Prime(Limit),24 Venza Limit,B52-D,G,F,H

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    I have the 16" low profile tires on the 2009 package 6 touring edition. Anyone have any direct results on those. I have them at 38PSI and will crank the front up to 40PSI this weekend. I saw another forum where someones mileage went down at 44 PSI. Strange!

    PS/ very hard ride on those low profile tires at 40 PSI. I have my Civic and Dodge at 42 PSI and the ride is nice.
     
  13. smartalec89

    smartalec89 The Official Alaskan

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    Just filled up after running around all the past week. 340miles on tank and 49mpg on screen. This is a definite improvement from the past tanks. I assume my mileage would be higher but I just put a roof rack on the car. I expect that my trip friday to be about 350miles. I will fill the car up before I leave and drive highway speeds (55mph) most of the trip. I plan on pushing the limits of the mpg and hopefully will get 50+mpg. I am setting a goal so I can stay focused on my driving. I don't know if I will meet it, but its worth a shot. Any suggestions to achieve this would be appreciated.

    Smartalec89
     
  14. richard schumacher

    richard schumacher shortbus driver

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    Remove the roof rack :_>

    OK, seriously: going slower always helps.
     
  15. ETP

    ETP 2021 Prime(Limit),24 Venza Limit,B52-D,G,F,H

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    Remove the roof rack//it stole 7 MPG from my Civic hybrid.

    PS/ I am up to 42/40 with 53.5 MPG. Do I dare go to 46/44?
     
  16. PA Prius

    PA Prius Active Member

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    I ran my Integrities at 50/48. I am now at 54/52 with my new GY Assurance Fuel Max.

    PA P
     
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  17. ETP

    ETP 2021 Prime(Limit),24 Venza Limit,B52-D,G,F,H

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    What size tires do you have?
     
  18. JimN

    JimN Let the games begin!

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    Block your grill, install an EBH & get a ScanGauge so you can see what's happening.
     
  19. PA Prius

    PA Prius Active Member

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    185/65 x 15. I see you have touring, so yours are a bit larger.

    PA P
     
  20. smartalec89

    smartalec89 The Official Alaskan

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    I think I will remove it. I will keep tabs on this trip just to see. Don't go too high the pressure might cause for poor driving comfort.