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new tires = 20 mpg drop?!

Discussion in 'Gen 3 Prius Fuel Economy' started by M K K, Jul 18, 2013.

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  1. M K K

    M K K Junior Member

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    Two days ago, I got Cooper CS4 tires to replace OEM on my 2011 Prius Three. Leaving the dealership my mpg went down to low 30's, about 35mpg. Prior to that I was getting 54-56mpg! Two days later, I'm still getting 32-33-35mpg around town. Called Toyota dealership and they said they'll take a look at it but that doesn't seem normal. I know it's not normal, jeez. What gives. Nothing is on, not the brake, not the ECO mode, not the power mode, so can tires cause such an enormous drop? No way am I driving a Prius that gets 30'smpg.
     
    #1 M K K, Jul 18, 2013
  2. Dan Cathy

    Dan Cathy Junior Member

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    Are those Cooper tires LRR? Also, check the tire pressure to make sure it's at 40 psi when the tires are cool
     
    #2 Dan Cathy, Jul 18, 2013
  3. ewxlt66

    ewxlt66 Active Member

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    Have you recently refueled?
     
    #3 ewxlt66, Jul 18, 2013
  4. sisharp

    sisharp Member

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    Check the visual alignment of the wheels. Do they generally seem straight? They could have got knocked out of alignment by a sloppy mechanic. I'd put the steering wheel straight and see where the wheels are pointing.

    Do you know if they rebalanced the wheels when they put the tires on?
     
    #4 sisharp, Jul 18, 2013
  5. Madduck

    Madduck New Member

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    Can having non-LRR tires make the much of a difference? My new-to-me Prius has Pepboys Futura HR Touring tires and I am getting 50 MPG.
     
    #5 Madduck, Jul 18, 2013
  6. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    #6 JimboPalmer, Jul 18, 2013
  7. M K K

    M K K Junior Member

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    JimboPalmer, thanks for the link! and the advice.

    Not LRR, but shouldn't be such a major drop, I wouldn't think. Alignment is good as far as eyes can tell. They did an alignment and balanced tires. Can't check pressure bc gage cannot be located at the moment.

    I'll update Monday after they check it out.
     
    #7 M K K, Jul 18, 2013
  8. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    I would expect a 5% drop with any new tire, as the diameter changes. 5% for LRR would not be impossible.

    After that, I am unsure where the MPG is going.
     
    #8 JimboPalmer, Jul 19, 2013
  9. sisharp

    sisharp Member

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    Any update? I'm interested in seeing what this was. It is so weird.
     
    #9 sisharp, Jul 23, 2013
  10. GrumpyCabbie

    GrumpyCabbie Senior Member

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    A big time YES.

    I had some fitted in error and my mpg's bombed. I'll always use LLR tyres in future. Worth the extra money, esp here with petrol over $8 a US gallon.
     
    #10 GrumpyCabbie, Jul 23, 2013
  11. theotherone

    theotherone Junior Member

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    I would recommend that you check tire pressures & get a tire alignment. They should be at a least 40psi (Front) and 38psi (Rear). I personally never trust the people at tire shops or dealerships to check my tire pressure, there are too many inconsistencies!

    Always check your cold tire pressure at least every 2 weeks or once a month (minimum), with a good tire pressure gauge.
     
    #11 theotherone, Jul 23, 2013
    M K K likes this.
  12. M K K

    M K K Junior Member

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    Update: I switched the Coopers with the Michelin Defender LLR. I consistently stayed in the 40mpg range with the Coopers. My mpg was at 42 the first day after switching, 47 the second and third, and by the end of the week, I'm sitting pretty up at 56-57, much better than pre-tire replacement!
     
    #12 M K K, Aug 2, 2013
    jgilliam1955 likes this.
  13. Former Member 68813

    Former Member 68813 Senior Member

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    This is a bizarre story. Does anyone have any plausible explanations? There is no way tires themselves would create so much resistance. Don't tires account for only 7% of energy loses?
     
    #13 Former Member 68813, Aug 2, 2013
  14. bwilson4web

    bwilson4web BMW i3 and Model 3

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    My tire gauge:
    [​IMG]

    Bob Wilson
     
    #14 bwilson4web, Aug 2, 2013
  15. M K K

    M K K Junior Member

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    Nice!
     
    #15 M K K, Aug 2, 2013
  16. M K K

    M K K Junior Member

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    Nope, no plausible explanation. No one can figure it out. I'm just glad it's all over; it was like an awful nightmare come true - kinda like sitting in a Starbucks drive-thru and wrecking your car ;) I paid an extra $25 per tire and another mount & glance fee equaling another $160 but I don't care. I will never try a non-LLR tire again.
     
    #16 M K K, Aug 2, 2013
    bwilson4web likes this.
  17. Kevine64

    Kevine64 Junior Member

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    Well crap, didnt know about lrr tir Goodrich Advantage T/A tires on it which I dont beleive are LRR tires..... Guess Ill see how well or crappy these things do. If I had known i would have tired to negotiate LRR tires into the deal..
     
    #17 Kevine64, Aug 9, 2013
  18. Kevine64

    Kevine64 Junior Member

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    I meant to say I just bought my car from the dealer and those are the tires it had on it in above post, they are brand new though so Dont really wanna pay for new ones already....
     
    #18 Kevine64, Aug 9, 2013
  19. Drdiesel

    Drdiesel Active Member

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    Non LRR tires will kill your MPG. The weight alone will make a huge difference.
    I took my stock 175/65/15 GY tires off and put on a set of new rims with new 195/65/15 Michelin Hydro Edge tires off my Civic. My MPG data showed the same as the OP's. After my new Kumho EcoWing 185/65/15 tires came in, it came right back up to normal.
    The Michelin tires added almost 10 lbs per wheel compared to the stock tires and wheels.
    Weight is as much a factor as LRR :eek:
     
    #19 Drdiesel, Aug 9, 2013
  20. Kevine64

    Kevine64 Junior Member

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    I do not know, maybe selling these off on craigslist and getting new ones. But then Ill have to get alignment and all. Not gonna be cheap at all :(
     
    #20 Kevine64, Aug 9, 2013
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