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Allowable tire sizes

Discussion in 'Gen 2 Prius Main Forum' started by derohanes, May 22, 2011.

  1. derohanes

    derohanes New Member

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    I have a 2006 Prius with the standard rims. A few years ago I read an article about changing tire sizes. I can seem to find that article, which cautions against going over a certain size due to excessive speedometer error and tire rubbing. I wasn't in the market for tires then, but I am now and can't seem to locate that thread. I found others, but they don't address the rubbing issue.

    Can anyone lend some guidance here?
     
  2. jdenenberg

    jdenenberg EE Professor

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    The standard Prius (non-touring) used 185/65R15 tires. You can alternatively use 195/60R15 since they basically have the same circumference, but are a bit wider. using 195/65R15 will work, but will change the calibration of your Odometer and Speedometer by about 2% (speedo will read lower).

    JeffD
     
  3. Hal W

    Hal W New Member

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    I put 195/65/R15 tires on mine. Next time I will go back to 185/65/R15. Runs about 3 mph low and the steering does not feel as precise! Hal
     
  4. F8L

    F8L Protecting Habitat & AG Lands

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  5. markaw

    markaw Junior Member

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    I'm thinking about getting Hankook Optimo H727 for my 2009 Prius (live in NY & VT).
    They don't make 185 65 15s, but do make 195 60 15.
    What might I expect by changing to this size from my OEM 185 65 15's
    Many thanks
    Mark Williams
     
  6. F8L

    F8L Protecting Habitat & AG Lands

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    Because the tire is shorter you can expect to throw your speedometer off a bit more than it is stock. So you may read 3mph too fast rather than 2mph too fast. Your MPG indicator might also be off a little more as well. It may read higher than actual (the gauge is already about 2% optimistic). Other than that there should be no issues. You will not harm the car.

    Use this calculator to figure out what to expect when changing tire sizes.
    Tire Size Calculator - tire & wheel plus sizing
     
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  7. LIPriusFreak

    LIPriusFreak Can I haz JDM?

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    you can expect better handling and a better footprint. they also seem to fill out the wheel wells better.
     
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  8. F8L

    F8L Protecting Habitat & AG Lands

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    Except that it is a slightly shorter tire which will result in more wheel well gap. I doubt it would be noticeable though. :) Thanks for adding the other benefits. I sometimes forget to do that. lol
     
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  9. LIPriusFreak

    LIPriusFreak Can I haz JDM?

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    I actually find my prius with less gap if u can believe it.....but 82k saggy springs help my wheel gap issue :D
     
  10. F8L

    F8L Protecting Habitat & AG Lands

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    I believe it. My 134,000 mile springs were sagging worse than Kriss Kross!

    [​IMG]
     
  11. LIPriusFreak

    LIPriusFreak Can I haz JDM?

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    don't hate....I still have warm it up on my ipod :cool:
     
  12. F8L

    F8L Protecting Habitat & AG Lands

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    It's on my flashdrive... Believe it or not they made it on a 250 Hits of the 90s CD. lol
     
  13. sktn77a

    sktn77a Member

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    I used 205/60x15 on my 05 Prius standard for a few years. Handled and braked better but the ride quality and mileage took a hit.
     
  14. calin8a

    calin8a New Member

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    New to the site and to the hybrid world in general but was curious if there are any concerns with mpg by changing tire sizes from factory: p195/65r15 to a bit wider style such as p215/60r15... any feedback is appreciated.
     
  15. F8L

    F8L Protecting Habitat & AG Lands

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    Yes, the wider the tire the more rolling resistance. Higher rolling resistance will cause a reduction in mpg. Some people do go wider for various reasons but I believe they go with a 205/60/15 but this size is actually smaller than an identical tire in the oem size. The 215/60/15 would be a tad larger than oem but may help correct the speedo error at higher speeds. It's off by 1-2 mph above 50mph. Expect to take a mpg hit with such a wide tire though.

    My 215/45/17s drop my mpg by at least 6 mpg compared to my 185/65/15s. Wheels weight the same as stock 15s.
     
  16. calin8a

    calin8a New Member

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    Thanks for the reply. I was also under the impression that Prius V comes with 17" wheels, and also wider tires... does that mean that particular model is less efficient than the others? I was just curious. Thanks again.
     
  17. F8L

    F8L Protecting Habitat & AG Lands

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    The V does come with 17s and yes it's less efficient. In every case where someone has upsized their wheels they have taken an approx 4+/-mpg hit. Those who claim otherwise usually do not track their mpg as accurately as those who observe the loss. I'm still waiting for a knowledgeable and reliable person to swap out the 17s on a V for a set of 15s and do a mpg test and not unreliable casual observations.
     
  18. calin8a

    calin8a New Member

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    hmm... that should be a very interesting test to perform. I would be quite interested as well if those results are actually published to learn from real world experience. Anyway, the information was very helpful!
     
  19. uart

    uart Senior Member

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    Hi Calin. The factory standard size in the US is 185/65. Going to 195/60 is a slightly wider upgrade tire that has approximately the same (though very slightly higher) revs per mile.

    BTW. 195/60 is actually the standard size tire in some countries, including Australia.
     
  20. sidecar

    sidecar Member

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    Its possible that there are a few colluding factors that make this more cloudy than it should be.

    1/ The thing that disturbs me most is the possibility that someone moves from 15" equipment to 17" equipment, and doesnt allow for the new rubber to be broken in.

    2/ The next thing would be poor choices in tyre diamters that effect speedometer and mileage readout.

    3/ The quality of the test regime overall, and consistency of application.

    one sure way of sorting this out is to get a co-pilot aboard with a good stop watch. Run some 1/4 or 1/8th mile times, say around 10 to even out reaction times, remove any flyers in the data. That removes any dependence on readout data

    With the usual caveats on equipment selection, if it takes longer with bigger wheel equipment then we know with certainty a performance difference in mileage to account for.