Recommend which tire pressures to run on my v:

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by El Cuajinais, Dec 11, 2012.

  1. El Cuajinais

    El Cuajinais Junior Member

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    Everywhere I read says increasing pressure improves MPG and handling. Increased MPG makes sense to me, however increased handling… this doesn’t seem like an intuitive conclusion. To begin with, I’m not even sure what is meant by “handling”. I would expect that having less tread on the road means less traction; and shouldn’t this play into the “handling”? I would expect the higher pressure you put into the tire, the more treacherous it becomes to drive on a wet road or in snow. However I’ve read that high pressures are better for snow, but I don’t know if people who say are simply suggesting this to offset the pressure reduction that occurs when you’re putting air into the tires at a comfy 70ºF garage and then drive your car at 20ºF outside. I’ve also read that more pressure makes for a stiffer ride because the tires do not absorb the bumps as well. This also makes intuitive sense. I would expect the shock absorbers to need replacement sooner in this scenario correct?

    So, getting to the Prius v: Sticker on the car says 35 front, 33 rear. Tire side walls says 40 max. Out of the dealer mine came with 36 on all four (all pressures in psig). I’ve increased the front tires to 38 so I’m running 38F, 36R. Not sure I’ve noticed a difference. Which pressures would you recommend I run at given that:
    a. I live Puerto Rico where the typical outside temp ranges only from 88ºF to 70ºF all year round.
    b. The roads here are in considerably poorer shape than US, Canada, and Europe. (More bumps and potholes)
    c. 85% of my mileage will consist of city driving.
     
    #1 El Cuajinais, Dec 11, 2012
  2. Cristino

    Cristino Junior Member

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    Hello,

    Mine is set at 38/36, it was 32/32 from the dealer. I've noticed steering is a bit more precise with the higher pressure (not as precise as my 'old' Mazda3 though but they're in different categories).

    Regarding the potholes, I just leave enough distance from the car in front to react to road hazards.
     
    #2 Cristino, Dec 11, 2012
  3. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    This is my take on tire pressure, it is just one man's opinion. Let me start with an exaggerated picture.

    [​IMG]
    In real life, the differences are not this clear cut.

    The under inflated tire will ride smoother, as the side wall of the tire has more flex, but will wear out on the edges long before the center wears out. All that side wall flexing will reduce MPG. Both sidewall flex and odd contact patch reduce handling and braking.

    The correctly inflated tire will last the longest as the more rubber touches the road, so less stress per square inch. It will not flex the side wall as much which helps MPG but allows more of the bump to come through the tire. Handling and braking improve with the larger contact patch, and the tread will wear evenly across the tire.

    An over inflated tire may get even better gas mileage, but at several costs. The small contact patch reduces handling and braking, reason enough for me not to over inflate. Tire wear is in the center of the tire only, and the sidewalls are rigid, so the tire offers no comfort compliance.

    My goal is to inflate my tires to get even wear, this varies by tire model and brand so you can't use a cookie cutter approach. However, on my gen 2, Toyota was about 5 pounds too low. The Integritys 'liked' 42/40, The Fuel Maxxs liked 37/35, and I never found the sweet spot on the Energy Saver A/Ss before it was run into by a semi trailer.

    Under no circumstance, inflate the tires beyond the limit printed on the tire! Anytime you feel the ride is too rough, lower the air pressure, this does not have to be torture. Toyota's specification really does provide the best ride.
     
    #3 JimboPalmer, Dec 11, 2012
    ewxlt66 likes this.
  4. jzchen

    jzchen Newbie!

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    I'd run factory pressure. The pressure is supposed to be set cold, ie in the winter conditions you mention it should be set at 20 degrees. If you are setting it at 70 and it is 20 degrees out, it is each 10 degrees is 1 PSI as I recall, so 5 PSI higher for the 50 degree difference. Higher pressure is more likely to develop a bubble in the tire when you hit these road imperfections as you mention about where you live....
     
    #4 jzchen, Dec 16, 2012
  5. skwcrj

    skwcrj Member

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    Checkout the Gen III Forum. There are pages covering this subject.

    A lot of old wife's tales are debunked there. Tire technology is completely different that it was 40 years ago. Check it out.
     
    #5 skwcrj, Dec 16, 2012
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