Prius Prime and spare tire

Discussion in 'Prime Main Forum (2017-Current)' started by gvp1995, May 22, 2016.

  1. ct89

    ct89 Active Member

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    This was actually an issue with the Gen2 and is documented in a number of threads in that forum. Toyota put 185/65/15 tires on the Gen2, my belief is to reduce cost and make the mileage look better. Those tires are about 2% smaller than the 195/65/15 tires they put on the Gen3.

    Toyota only did this in the US. European Gen2 models had the 195/65/15 tires and people eventually noticed that if you actually put the 195/65/15 tires on a Gen2, your speedometer was now accurate vs. a GPS. As I recall, the car was actually calibrated to accommodate a 25" diameter tire and apparently Toyota never changed those calibrations when they chose to put the smaller tire on the US versions. I ran with 195/65/15's for years on my old Gen2 with no issues.

    Using the smaller 185/65/15 tire will result in a 2% error (you will actually be going slower than the speedometer indicates and getting fewer MPG than the display shows) but it will otherwise work fine...
     
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  2. Mendel Leisk

    Mendel Leisk Senior Member

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    The speedometers are intentionally meant to read high (by mandate I think?), the object being to err on the side of slowing down.

    How about the odometer? I would suspect it would be calibrated to be as accurate as practical, with the stock tire size.

    The displayed mpg is another matter, acknowledged by all (except the liar in the room) to be grossly optimistic.
     
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  3. Lee Jay

    Lee Jay Senior Member

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    On long trips, I've compared the computer estimate to that measured at the pump. Average is within 1.5%. Since the pump accuracy is only guaranteed to 3%, this is within the error bars of the test.
     
  4. Mendel Leisk

    Mendel Leisk Senior Member

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    Maybe 4th gen and Prime is more accurate? My 3rd gen, with 142 tanks tracked for mpg (virtually since the car was new), the disparity between displaced and calculated is 7.4%, optimistic of course.

    Also, I would think gas station pump accuracy would fall on either side of spot-on. And I don't see the point in using that, to justify Toyota's (very likely intentional) inaccuracy.
     
  5. Andyprius1

    Andyprius1 Senior Member

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    The displayed MPG is really MPGe, to include ICE and ev operation. It’s especially fanciful in the beginning with its 199.9 reading. Whatever is calculated at the pump is most accurate, but even that’s subject to large errors.
     
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  6. Mendel Leisk

    Mendel Leisk Senior Member

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    I've seen only modest errors. That's while managing to be sole person tanking up, using similar technique. Any errors tend to be on a single tank, due to a pump's automatic shut-off activating a bit earlier or later, and balance out with the next tank.

    The main spanner in the works tends to be when someone borrows the car and tops it up for you. As long as they've retained the receipt, you can at least just lump it in with the next tank.
     
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  7. Andyprius1

    Andyprius1 Senior Member

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    Agree
     
  8. Dudley1030

    Dudley1030 Active Member

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    Just bought 15x7 American Racing AR919 BLACK MACHINED wheel for my spare. Putting a 195/65R-15 Michelin Energy Saver A/S tire on it. The wheel weighs 15.75 lbs. The tire weighs 18 lbs. So adding 33.75 lbs to the car. If I like it, I might buy 4 more and run them all the time! Pic below. Click it and go to the site. To make up for the additional weight;), I'll only be able to put 1/2 tank of gas in my Prime.;)
    wheel 2.jpg
     
  9. Lee Jay

    Lee Jay Senior Member

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    No, that displays a total misunderstanding of what both MPG and MPGe are.
     
  10. benagi

    benagi Active Member

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    Nice looking wheel. Have you mounted the tire and wheel on your Prime yet to make sure it is a proper fit? I’m looking a purchasing a spare for road trips.
     
  11. Dudley1030

    Dudley1030 Active Member

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    Not yet. Tire Rack assured me it would fit.
     
  12. mahpham

    mahpham New Member

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    Can someone recommend a spare tire for Prius Prime 2017 Plus that is not too big and heavy?

    I saw one post mentioned 2016 Prius compact spare wheel (Toyota Part Number: 42611-47630) or Yokohama Y870C. Anybody else got these?

    Thanks!
     
  13. Andyprius1

    Andyprius1 Senior Member

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    I did end up using this spare after the accident, traveling about 35 miles to home, 50% freeway. Remember, top speed is 50 mph with doughnut spare. When I got home, I put my full size spare on...........So I do know, the DOUGHNUT from 2005 WORKS and.....
    I suspect, that, to date: that doughnut works on any other Prius Hybrid. All the doughnuts are the same!

    THE DEALERS DO NOT KNOW THIS.
    all they could tell me upon purchase, was Toyota doesn’t make a spare for the Prime. Schmucks!
     
    #273 Andyprius1, Jun 25, 2018
    Last edited: Jun 25, 2018
  14. bisco

    bisco cookie crumbler

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    schmucks should always get a like.
     
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  15. schja01

    schja01 One of very few in Chicagoland

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    Are compact “donut spares” typically factory balanced?
     
  16. Salamander_King

    Salamander_King Senior Member

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    You resurrected the longest thread on our favorite topic on PRIME. LOL
    I think if a donut spares comes originally with a car, it would have been balanced, but not sure. If not, any tire shop can check and balance it, I think. But would it be that important? Having 50 miles at 50mph max speed limitation and donut being not identical to the rest of tires on the car, maybe even slightly unbalanced donut spare is still acceptable? IDN.o_O
     
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  17. Mendel Leisk

    Mendel Leisk Senior Member

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    You realize this means I have to drag mine out, and look for weights...

    I'm just gonna wing it (for now, but I'll probably snap and go check): I don't recall seeing weights. Anyone else?
     
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  18. schja01

    schja01 One of very few in Chicagoland

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    I purchased a rim and tire from the dealer and it wasn't balanced. I questioned it and was told basically the same thing: 50 mph/50 miles wouldn't require balancing.
    So I just got off my lazy arse and after cleaning out 10 tons of junk checked the donut in my wife's Venza.

    No weights.

    Thanks for the replies.
    J
     
  19. Salamander_King

    Salamander_King Senior Member

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    How are you securely storing the compact spare in your Prime? Have anyone come up with good idea to tie (bolt) it down? After reading @HPrimeAdvanced having third flat on his PRIME without spare tire on board, I decided to bring a full size spare in a car which had been safely stored in the garage. It fits perfectly behind front passenger seat. By folding down rear seat with headrest removed, it is so tightly wedged in, so that it is not likely to move out of the place except in severe side impact and/or rollover accident. I still would like to have it secured down, if there is any good idea.
    IMG_20180920_175807.jpg
     
    #279 Salamander_King, Sep 21, 2018
    Last edited: Sep 21, 2018
  20. Mendel Leisk

    Mendel Leisk Senior Member

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    The only thing that sucks: now it's a three seater. :(
     
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