NTB put on wrong size tires... Need Advice!

Discussion in 'Gen 2 Prius Main Forum' started by newkbomb, Jan 23, 2007.

  1. newkbomb

    newkbomb New Member

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    I had some Michelin Hydroedges put on 4 days ago and just noticed that NTB actually put on 195/60/15's instead of the factory recommended 185/65/15. What will happen? I can tell they are wider and actually look better... but is it going to effect my MPG? Also, is this going to effect the accuracy of my spedometer? Should I get them swapped or stick with the 195's? Looking for some advice. Thanks!
     
  2. hobbit

    hobbit Senior Member

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    One reason I went with a local place instead of a Clueless
    Hulking Corporation...
    .
    A wider tread will generally produce more rolling resistance, yes.
    .
    To calculate odometer error, do you know the revs / mile figure,
    for starters? Compare that to the 855 of the OEMs. Then again,
    my "exactly correct" Hydroedges were 1.3% off from where I thought
    they'd be, with a measurably smaller circumference, so maybe the
    tire manufacturers just don't really know.
    .
    _H*
     
  3. newkbomb

    newkbomb New Member

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    revs/mile for the 185's is 850.3 and it's 859.1 for the 195's. So does this mean that if my speedometer reads 70 then I'm really only going like 68 or something? How much % do you think I should calculate for? Can I get a setting changed at the dealorship to account for 195's so my speedometer will read correct?
     
  4. JimN

    JimN Let the games begin!

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    <div class='quotetop'>QUOTE(newkbomb @ Jan 23 2007, 07:59 PM) [snapback]379789[/snapback]</div>
    The revs/mile are within about 1% of each other presuming both numbers are accurate. At 70mph the indicated difference in speed is 0.72mph, shouldn't be enough to notice.
     
  5. Allannde

    Allannde Just a Senior

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    <div class='quotetop'>QUOTE(newkbomb @ Jan 23 2007, 04:59 PM) [snapback]379789[/snapback]</div>
    That adds a 1.07% error to a similar error which comes from the factory for about a 2% error. In other words at 100 mph indicated you would actually be traveling about 98 mph. At slower speeds the error is less noticable. For example at an indicated 30 mph you are actually traveling at about 29.4 mph.

    Is that enough to worry about or is it just a little insurance against a traffic ticket?

    Of course when the odometer says 100,000 miles, you will have really travelled only 98,000 miles.

    I have never heard of adjustments to the speedometer/odometer to make up for different tire size.
     
  6. donee

    donee New Member

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    <div class='quotetop'>QUOTE(newkbomb @ Jan 23 2007, 09:59 PM) [snapback]379789[/snapback]</div>
    Hi Newkbomb,

    That 859.1/850.3 is 1 percent faster speed for the same speedometer reading (final drive revs) with the 195's. As speedometers are typically calibrated 2% low (ken1784 link to U.N. document), the 195's will probably give you a spedometer reading closer to your actual speed.

    In fact, a guy with a GPS confirmed this fact in an old thread.
     
  7. rfred

    rfred New Member

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    <div class='quotetop'>QUOTE(newkbomb @ Jan 23 2007, 05:07 PM) [snapback]379749[/snapback]</div>
    Enjoy the 195's and rest assured that you are driving on tires that are much more safe than the original tires that came with the car. Someone from Toyota owes us an explanation for why such a fantastic car is sold in the U.S. with such (insert derogatory adjective of your choice) tires. They would be fine if we all lived in Southern California or Florida and it never rained...
     
  8. dmckinstry

    dmckinstry New Member

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    <div class='quotetop'>QUOTE(rfred @ Jan 23 2007, 05:36 PM) [snapback]379803[/snapback]</div>
    And believe me. It rains in Florida. Haven't been there since I got the Prius though.

    Dave M.
     
  9. Beryl Octet

    Beryl Octet New Member

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    <div class='quotetop'>QUOTE(newkbomb @ Jan 23 2007, 06:07 PM) [snapback]379749[/snapback]</div>
    I'm going to switch to that size when the Integrities wear out. I don't think I'll notice the difference in the speedometer or odomoter. They might impact MPG slightly, but I think the improved grip would be worth it. If they sold them to you for the same price as the 185's then you got a bargain. The 195/60's are standard equipment in Europe or Japan, I think, too.
     
  10. newkbomb

    newkbomb New Member

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    Thanks for the help everyone... think I will definetely stick with the 195's. The really do look a TON better than the Integrity's and it sounds like they'll handle better too. :)

    Also... found this cool site that compares different sizes of tires. And you guys were correct... this website shows that if the speedometer reads 70 then I would actually be going 69.26 MPH.

    http://www.discounttire.com/dtcs/infoTireM...pnbgCp8TVg7PzGK
     
  11. JimboK

    JimboK One owner, low mileage

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    <div class='quotetop'>QUOTE(rfred @ Jan 23 2007, 08:36 PM) [snapback]379803[/snapback]</div>
    What makes them so much safer?
     
  12. jdenenberg

    jdenenberg EE Professor

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    <div class='quotetop'>QUOTE(JimboK @ Jan 24 2007, 07:21 AM) [snapback]379968[/snapback]</div>
    Jim,

    The Michelin Hydroedges have much better traction in wet weather than the OEM Goodyear Integrity tires (the Integrities really are not very good tires). The downside is a drop in MPG.

    I use the Michelin MXV4+ " Energy Saving" tires which actually improved my MPG somewhat over the OEMs, improve the handling (as will the Hydroedges), and are only a little less capable than the Hydroedges in wet/snow conditions.

    JeffD
     
  13. JimboK

    JimboK One owner, low mileage

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    <div class='quotetop'>QUOTE(jdenenberg @ Jan 24 2007, 09:42 AM) [snapback]380010[/snapback]</div>
    Thanks. It looks like I mis-interpreted his post. I first read it (probably too hastily) as saying 195s are much safer than 185s, which I question. On the issue of the tire brand and model, I have seen enough on the forums to convince me there's a better tire than the Integrity. "Much safer" may be a stretch, but certainly one that has better bad weather traction, lasts longer, and rides and handles better.

    In fact, the Energy MXV4+ is my top candidate at the moment for when I replace my Integritys, probably before next winter. (I have 20K on them now.) Can I assume you're pleased? How many miles do you have on them?
     
  14. kn6vv

    kn6vv Junior Member

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    <div class='quotetop'>QUOTE(jdenenberg @ Jan 24 2007, 07:42 AM) [snapback]380010[/snapback]</div>

    JeffD,

    I have been planning for a while to replace my OEMs with the MXV4 for the same reasons you mentioned. My question is what size did you go with and how it compares to the 855 revs/mile the OEMs are? I wish to keep my speedometer error to a minimum. Thanks!

    Tom - KN6VV
     
  15. David Beale

    David Beale Senior Member

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    The 195s may be safer than the 185s just due to load carrying capacity, but you'd have to look those numbers up in a manufacturers book to be sure. Usually (but not always) larger tires have a higher load carrying capacity, which also translates to less flex on cornering, and less chance of damage when hitting road "irregularities". Larger tires can also allow you a greater range of running tire pressure, as you can safely run them at a lower pressure. Load carrying capacity is proportional to tire pressure, hence you read on the sidewall "max. load carrying capacity XXXX lbs at XX PSI."

    As far as running resistance, you can't be sure a larger tire will have a higher running resistance. It depands on many factors besides size, including tire rubber compound, tire shape, tire design (placement of belts etc). The size difference in this case is small (1 cm width with lower sidewalls), so they may have close to the same running resistance anyway.
     
  16. Beryl Octet

    Beryl Octet New Member

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    <div class='quotetop'>QUOTE(kn6vv @ Jan 24 2007, 10:13 AM) [snapback]380023[/snapback]</div>
    tirerack.com shows the 195/60 15's at 862 revs per mile. Within 1%, not noticeable I'd expect. I'm going for these when the Integrities get a little more worn.
     
  17. koa

    koa Active Member

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    I put 205/60 15 Michelin Pilot Exalto A/S on my Prius. Other than the hit in mileage I noticed there is a lot more road grime that gets thrown on the side of the car by the wider tires, and that is with the mud guards installed.
     
  18. FreshAirGuy

    FreshAirGuy New Member

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    I deliberately put 4% larger tires and 17in chrome wheels on my 2005.
    The car handles a lot better. The ride is a little stiffer.
    In six months my MPG av dropped from 45 to 44.
    I get a lot of compliments on how the car looks.
     
  19. cobra94563

    cobra94563 Junior Member

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    MXV4's.....check tirerack.com for reviews.
    They were oem on our honda. good wear but not terrible in wet and overpriced. There is a lot of choices of better tires, IMO.
    (But it your $ to spend.)
     
  20. Beryl Octet

    Beryl Octet New Member

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    <div class='quotetop'>QUOTE(cobra9 @ Jan 24 2007, 12:01 PM) [snapback]380103[/snapback]</div>
    Any specific suggestions? I was looking at the MXV4's because of the low rolling resistance, and I had put a set on my previous car and really liked them. I'm not wanting to impact mileage too much, would like better wet handling (I think anything would be a step up from the Integrities), and maybe better dry handling, assuming wet handling and mileage are not traded off.
     
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