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tire pressure upgrade on 08 touring edition

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by fbret, Jul 9, 2008.

  1. fbret

    fbret New Member

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    I just filled up for the first time my prius :)
    I wanted to up the tire pressure to 42/40 as recommended on the board, but noticed the tires say "do not inflate over 40psi"...
    what to do?

    -Fred
     
  2. Sheepdog

    Sheepdog C'Mere Sheepie!

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    thats up to you fred but my tires are 42/40.
     
  3. eclipse3g

    eclipse3g Junior Member

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    My 08 Touring #6 is at 42/40 psi. Has been for the last 5000+ miles.
     
  4. richard schumacher

    richard schumacher shortbus driver

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    It is not advisable to inflate tires above the maximum rating given on the sidewall. The 42/40 PSI front/rear commonly reported here applies to the non-touring Goodyear Integrity tires, which have a maximum rating of 45 PSI.
     
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  5. hiremichaelreid

    hiremichaelreid New Member

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    The Touring tires are sidewall rated for 50 PSI.

    I've been running 50/48 for 4 weeks. I'm now trying 40/38 to see how handling improves and MPG deteriorates. I'm more concerned about traction and safety (and avoiding expensive collision repair bills) than a few pennies in my wallet today.
     
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  6. krmcg

    krmcg Lowered Blizzard Pearl Beauty

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    My 2008 Touring Package 6 has the 41 max tires. I inflated them to 41 all-around without a worry in the world.
     
  7. Sheepdog

    Sheepdog C'Mere Sheepie!

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    I believe the better formulation would be to drop the rears by "2psi" from the fronts. Handling and weight distribution will benefit.

    so 41/39 is a better way to go than 41 all.
     
  8. steve39

    steve39 New Member

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    Do you have fear any of using those fully inflated tires with a full load and/or on a hot day?
     
  9. carjon

    carjon New Member

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    Just a reminder especially for those whose pressure is on the edge or over limits, pressure will vary greatly with outside temperature. If you live in a cold area and haven't checked / adjusted lately you should. If you have when / if it gets warm again make sure you check them and let out air if needed.
     
  10. Celtic Blue

    Celtic Blue New Member

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    It's important to have the tire fully inflated for a full load. The lower the inflation pressure on a full load, the more likely the tire is to fail if I understand correctly. So in the case you named higher is better.

    Tires generate heat while running. The more pressure, the less heat they tend to generate because the sidewalls flex less. This is somewhat self regulating as higher rubber/air temp results in higher pressure. Internally generated heat is the enemy of the tire. If you run pressure too low the tire will get too hot and although the pressure will rise as a result, it will probably not be enough to save the tire from failure.

    Someone who did tire design work (or similar) posted about this a few months ago and if I remember correctly there is a lot of safety factor built into the sidewall maximum. I'm pretty certain the person stated that the operating temperature (versus cold inflation pressure) is factored into the design. This is probably done for the max speed rating as well (but I don't remember if that was addressed)...and that is well above where most of us operate our tires.
     
  11. jdel

    jdel New Member

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    Recommended tire pressures are always when cold. A hot (driven 4+ miles) tire pressure can increase by as much as 4 psi. A tire thats set to 42 psi cold will rise to 46 psi when hot. If you set your tires to the maximum on the side walls cold, you are in danger of exceeding this when the tire heats up.
     
  12. donee

    donee New Member

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    Hi All,

    I think the best pressure to run tires at, for everyday driving, is the pressure that results in an even wear across the whole width of the tire. In a US Prius with 165 sized tires thats somewhere between 40 and 44 PSI front, and 2 psi lower in the rears.

    For the touring guys, measure your tread depths with a caliper, write em down. Then run the car for 10K miles at one pressure. Then check the tread depths again. If its wearing more on the edges, a higher pressure is indicated. If more in the middle of the tread, a lower pressure should be set.
     
  13. josh2008

    josh2008 Active Member

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    I think some of you are confusing the "do not inflate above 40psi to seat bead" with the "maximum side wall pressure". You never want to exceed 40psi when mounting new tires on the wheels(seating the bead). However max sidewall is where you want to be, wellin my case i'm a little over. For example, my integrities say do not exceed 40psi while seating bead, but, if you look on around the side it says max 44 sidewall psi when cold. This means when the car hasn't been driven anywhere 44psi is ok, they take heat expansion while driving into consideration so need to worry. Just set your tires your tires at max sidewall and have you no worrys. =) Hope this helps clear things up some and for what its worth i've been running 54/52 for the past 7k or so and still noticw more outside wear so they are now at 60/58. Having owned a lowered car before a little roughness from increased psi is nothing compared to a lowered car.

    Happy motoring!
     
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  14. josh2008

    josh2008 Active Member

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    Sorry for the crappy grammer/spelling. There doesn't appear to be an "edit" button when your on PC mobile.
     
  15. Mochabuzz

    Mochabuzz Junior Member

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    I have falken ziex 912 tires. They are a few months old. I recently inflated them to 44/42psi. They seem to be okay. They were 35/33 before & my mileage suffered.
     
  16. theshark

    theshark Member

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    Unfortunately I don't see any improved fuel mileage when I ran 42/40, no increase at all. I run the door jam pressure 35/33 The mileage stayed the same.
     
  17. Britprius

    Britprius Senior Member

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    Surely the US touring version runs 195/55/16 tyres the same as UK/European Prius. The extra width allows slightly lower pressures without loosing MPG or stability. In fact going even wider to 205/55/16 shows even more benefit.

    John (Britprius)