Tire pressure question

Discussion in 'Prius c Fuel Economy' started by dunston, Oct 14, 2012.

  1. steveoknievo

    steveoknievo Member

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    In your Prius C? :eek:
     
  2. RocMills

    RocMills Active Member

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    I noticed recently that our mileage had decreased, even when I drive sans a/c. Then I was sure I heard the tires squeaking in the parking lot (hubby thought it was another car, not ours). Yesterday, I had the tires inflated to 42 ... and I have already noticed a decent increase in mileage. A trip that last week I had to struggle and hypermile to get 58, today got 72 with no special effort at all.
     
  3. johnhlong

    johnhlong Junior Member

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    My new Prius C2 came from the dealer with 50/50 psi.

    I called them and they checked and said that that is what they ship them with on the train or truck from the factory.

    He apologized and said the service person should have adjusted them to 35/35 psi before delivering the vehicle.
    He further checked the service record on my car and a certain service person is in for a long talk tomorrow:rolleyes:

    I'm going to adjust them to 42/40 as I saw some posting on here.

    So for me maybe I'll get a smother ride?


    John
    2013 Prius C2
     
  4. Skylis A

    Skylis A Senior Member

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    Yes... I've noticed that the ride can be a little rough when my tire pressure is above 42 psi.
     
  5. Andyprius1

    Andyprius1 Senior Member

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    that sidewall pressure is simply the pressure at which the tire will seat on the rim, only the tire mounter is interested in that pressure rating. Although in actuality the tire mounter must use higher pressures than that to usually get the tire to seat on the rim. On my 2005 Prius I ran recommended car door pressures and had to replace them at about 25000 miles. My second set, I kept at 40 - 55 until I sold the car at 105,000. My Pip, I keep at 55 and when the pressure reaches 40, the low Pressure warning goes off and they get reinflated to. 55 again. I plan to keep the C pressures up around 50. The sidewall pressure is a good starting point and can later be reevaluated to individual taste. The car recommendations will definitely lead to quick wear.
     
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  6. xraydoug

    xraydoug Active Member

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    On my tires it states max psi to mount tires on rims at 40, it also states max air psi for tire at 44. I have no doubt that the tires will perform well at stated max pressure. and are safe at that. (y) Tires usually wear out on the sides and use extra gas if inflated to the car reccomended pressure. :(

    I believe you do increase your risk of road hazard tire failure with a tire inflated to max rated pressure, or even above that as stated in your post.:unsure: I keep mine at or just above the max pressure on sidewall, I only have 600 miles on my prius c, but have used these pressures on other cars for years. Some people say you lose traction ect. but IMO my cars seem to have great traction except in sand or snow in that case lower them to car reccomentded pressuer.

    PS great choice in cars I think it is the same color as mine:)
     
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  7. mahout

    mahout Active Member

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    The max pressure molded in the sidewall is the maxiumum cold tire pressure you should inflate the tire to. While it is true increasing te pressure to 40 psig will yield better mpg it is also true you should not inflate to 50 psig because at higher speeds the tire will gain added pressure and will reduce the traction of the tire; its a good rule for street and highway driving to inflate the tires to no more than 10 psig less than the max pressure.
     
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  8. xraydoug

    xraydoug Active Member

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    In our camry hybrid the tires ar inflated to the max rated pressure, using the tire pressure monitor they have never gained over 3 psi. on trips traveling at 65-75mph and I have been running tires at rated tire pressure for many years. the only tire failure I have had was a tire on our fifth wheel that was under inflated it got hot on the freeway and failed.(y)
     
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  9. Andyprius1

    Andyprius1 Senior Member

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    Underinflation, that is really the major problem.
     
  10. Priusxrs

    Priusxrs Junior Member

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    100mph...unless u dont mean with a full battery ive been over 110mph in my c with heavy 17s at 50psi

    SGH-T889 ? 2
     
  11. mahout

    mahout Active Member

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    Interesting. What 17" tires ? Verified how ? ours verified by track measuring devices aka radar and electronic timing strps.
     
  12. Priusxrs

    Priusxrs Junior Member

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    Pendot state trooper is one 2 would be the speedo and 3 would be my gps on my phone the tires are 205 40 17 nexus if I remember right my cars in the shop atm for a new axle

    SGH-T889 ? 2
     
  13. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    My take: the sidewall pressure is the maximum pressure the consumer should set them at, when the tire's in use. Isn't there a proviso with that pressure label, something along the lines of " with max load..."?

    You can likely go higher, there's a healthy buffer in that value, but that's the intent of the label I think.
     
  14. xraydoug

    xraydoug Active Member

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    I think that max sidewall pressure is stated on tire. and the tire is made to work with that pressure. It may work fine with higher pressure but that is not the classification. tires seem to have certain numbers. like some say 44 psi but I havent seen any 47, 48, 49, psi ? then there are some that say 51 but no 52-65 I think. so I am pretty sure there are certain guidelines that determine max pressure rateing for tires.

    The less pressure a tire has in it the more heat it will gain while driving. due to friction caused by sidewall flex. this heat is the most common cause of sudden failure. ie blow out, alos low pressure will always cause a tire to wear on the edges.

    over inflation can cause a tire to wear on the middle, or more likely to fail due to road hazard like sharp rocks or pick up a nail ect...

    So I won't run a tire under car makers suguest pressure, and am cautious of going over max sidewall pressure. my prius c stays in town almost all the time, and I am at 50 psi and my mpg is great. (y)
     
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  15. mahout

    mahout Active Member

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    The diameter of a Nexus 205/40x17 is slightly smaller than OEM so the combination of better gear and revs per mile could show more mph; the gps should be good but if the run had any downhill at all 110 is entirely doable. In any case you should do a up/back average to find out what you're max speed is.
     
  16. Larry Greenwald

    Larry Greenwald Junior Member

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    Look, any pressure above factory spec is good. Tires do lose air from micro leaks, so if you have it higher all around, you're better off. I had my Toyota dealer set it at 40 PSI all around during the 5K service and all's well. My MPG overall has gone up too.
     
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  17. jack520

    jack520 Member

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    Rolling resistance is rolling resistance.

    You have to burn energy to overcome it.

    From my understanding of physics, the same mpg impact is there at high speeds as it is at low speeds.

    So you would loose the same MPG reguardless of the speed.
     
  18. xraydoug

    xraydoug Active Member

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    I agree, higher psi always gives better mpg in my car. You should not go over the max psi listed on sidewall of tire.(y) That way you know the tire is designed to run with that psi
     
  19. benkhanobi

    benkhanobi Member

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    I wouldn't want to increase the tire pressure more than a couple psi, as I don't want to put extra stress on the suspension. Higher tire pressure causes higher G force loads and can cause oversteer- none of that is good.
     
  20. james cook

    james cook Member

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    I could hardly get 50 mpg at 40/38, 42/40.

    I put 44 in my front and 40 in my back (44/40)and now I'm getting 57 mpg
     
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