Correct me if I'm wrong on tire pressure.

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by FishHawk, Apr 12, 2007.

  1. FishHawk

    FishHawk New Member

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    So here is what I have concluded from reading most of the threads on tire pressure and mileage. Most people over inflate their tires to get the great mileage . However, when the tires heat up the pressure increases by at least a couple of pounds which will put the tires at or near the max specs for that particular tire.
    The premium tires can handle the higher pressures but the OEM tires will not hence the poor and often dangerous handling with the OEM's.
    My dilemma is when my OEM"s wear out what tires to get. I will probably get the tire that is close to the OEM'S . Looks like the Comfort Treat tire is closest. Thanks for your input. FishHawk
     
  2. morpheusx

    morpheusx Professor Chaos

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    <div class='quotetop'>QUOTE(FishHawk @ Apr 12 2007, 07:27 AM) [snapback]421958[/snapback]</div>


    I just picked up my '07 about 2 weeks ago and I checked the PSI and they were inflated to 38.5 on all four wheels, I went ahead and left them where they were at and drove it down to Virginia Beach and North Carolina from Akron, OH and was able to pull down 50 MPG on the way down and felt the handling was pretty good too, even on that horribly twisty PA turnpike.
     
  3. Betelgeuse

    Betelgeuse Active Member

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    <div class='quotetop'>QUOTE(FishHawk @ Apr 12 2007, 06:27 AM) [snapback]421958[/snapback]</div>
    I believe that your fact is right, but I take issue with your interpretation and conclusions. Many people here do inflate their tires to beyond what Toyota recommends. However, very few (if any) inflate their tires to beyond what the tire is rated for. It is also important to realize that the pressures quoted (both in the manual and on the tire sidewalls) are cold tire pressures; the pressure is meant to be measured while cold. Of course, the tire manufacturers realize that the tire will heat up while driving, and that's accounted for in the "max pressure" notated on the tire sidewall. I've never noticed any poor or dangerous handling with my tires at 42/40. From what I can tell, the claims of "dangerous" freeway handling that a small fraction of Prius owners have experienced seem to be independent of tire pressures.
     
  4. jdenenberg

    jdenenberg EE Professor

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    <div class='quotetop'>QUOTE(FishHawk @ Apr 12 2007, 07:27 AM) [snapback]421958[/snapback]</div>
    Betelgeuse is correct in his analysis. Your Goodyear Integrity tires are rated at 44 PSI max COLD so what most of us do (42/40 in my case) is safe. I replaced my GYs with Michelin MXV4+ "Energy Saving" tires and had very good results. The "Comfort Treads" are fine tires but will impact your MPG somewhat (2-3 MPG lower than the GYs). The MXV4+ tires will improve your MPG a little in cold weather and do about the same MPG as the GYs in warm weather.

    The MXV4+s are not great in snow, so if that is a concern, take a look at the Nokian WR tires to get good snow traction as well as good MPG.

    JeffD
     
  5. aaf709

    aaf709 Ravenpaw of ThunderClan

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    <div class='quotetop'>QUOTE(FishHawk @ Apr 12 2007, 03:27 AM) [snapback]421958[/snapback]</div>
    I have the ComforTreds and am happy with them, but there are other tire choices. Take a look at this topic for other ideas.
     
  6. darelldd

    darelldd Prius is our Gas Guzzler

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    Also, a harder tire will heat up less than a softer one.

    As others have said - the pressure rating is a COLD rating. Doesn't matter if pressure increases over the "limit" when warm.
     
  7. amacd

    amacd Junior Member

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    <div class='quotetop'>QUOTE(FishHawk @ Apr 12 2007, 04:27 AM) [snapback]421958[/snapback]</div>
    Yes, you are wrong in that the specified tire pressure is measured COLD. The rise in pressure is taken into account by the manufacturer and if you lower the pressure because you are driving on hot pavement at high speeds, then you have the WRONG pressure. The Prius OEM tires can stand the 100 MPH that the car can go, but I am not going there, even on a track.
     
  8. philmcneal

    philmcneal Taxi!

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    i've been running over 50 psi cold in my tires for over 6000 km, I had one small screw into my tires but by the time it was time for me to use my car again the tires had no more air left. So if I were to imagine my tires were at 30 psi and I ran over that same screw, I highly doubt I'll make it back home with any air left.


    Some food for thought about high tire pressure, I've been a 50 60 psi guy for YEARS.

    At this point of my life 40 psi is "low" in my terms believe it or not.

    If you do decide to flame me for my high psi about safety you can simply hear the last of me.
     
  9. cc9150

    cc9150 New Member

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    Are you putting others on the road in any danger by running such high pressures?
     
  10. FireEngineer

    FireEngineer Active Member

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    A lot less than all the people running with low pressures.

    Wayne
     
  11. qbee42

    qbee42 My other car is a boat

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    I think you are missing the point about the OEM tires. The OEMs give good mileage, even at Toyota's recommended pressures, but they are crappy tires. That's the point: Goodyear Integrities just plain suck, that's why people switch them out for better tires. I ran my OEMs at Toyota's recommended pressures, and I run my new Michelin MXV4+ Energies at the same pressures. I'm not sure it's safe to assume that most of us run at higher pressures. You will see a lot of posts from people that use higher pressures, but that's because they are a self-selected group that is trying for the best possible mileage. The rest of us are happy with merely great mileage. I average 55-56 mpg in the summer, with stock tire pressures.

    Tom
     
  12. priusFTW

    priusFTW Gen III JBL non Nav

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    <div class='quotetop'>QUOTE(FishHawk @ Apr 12 2007, 07:27 AM) [snapback]421958[/snapback]</div>
    Seeing that you are from Holliston MA, you probably experience some snow like I do to the north of you in New Hampshire. You may wish to look into the Nokian WR's, a very good all season tire. I swapped out my OEM tires for them very soon after delivery. The salesman gave me credit towards the Nokian's. The Nokian WR's btw come in the exact same size as the original OEM tires.

    Oh and I didn't notice any MPG drop, I average about 54-57 MPG and I have them inflated 42/40.
     
  13. andyprius

    andyprius Senior Member

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    <div class='quotetop'>QUOTE(philmcneal @ Apr 13 2007, 11:36 AM) [snapback]422711[/snapback]</div>
    It's difficult to critisize your success at driving your cars at 50-60lbs pressure. However most Prius/ Honda sidewall pressure warnings are at 40-44lbs. I suppose larger cars and trucks are rated at higher pressures. My RV bead pressure is at 60lbs so I keep the tires at that pressure. The only reason car companies recommend lower pressures is for a soft ride. They are not concerned about higher loads, higher speeds or mileage. Bead pressure will not assure higher mileage, but will add to safety. Have you ever measured the center tread as compared to the outer tread when driving on a long term basis at 50-60lbs?, after 20,000 to 30,000 miles. 6000KM (3600 miles) is not an adequate test. :rolleyes:
     
  14. andyprius

    andyprius Senior Member

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    <div class='quotetop'>QUOTE(cc9150 @ Apr 13 2007, 01:01 PM) [snapback]422816[/snapback]</div>
    What is high pressure? The sidewall (bead) pressure is the highest pressure you should use. That pressure is basically recommended for the tire installer. ( putting tires on rims ) He's working at ambient temperatures. A driver running with overbead pressure (cold) runs the risk of instability, skidding, a blowout, tires getting so hot they literally melt and last but not least you have a ballon tire and your center tread wear will be excessive. BOTH overinflation and underinflation are dangerous.
     
  15. Mr.Vanvandenburg

    Mr.Vanvandenburg New Member

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    Mine were also 38 lbs from factory. I decided to put them back to the 35/33 yesterday. Seems to ride better and handle better on highway, to me anyway, no problem in wind so far. One thing is that 35 is already a very hard tire in my book, I normally run 30 in the other car(s). It seems to me a too hard tire will be harsher on the suspension, and the back.
     
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