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New Tires will probably show lower MPG's...

Discussion in 'Gen 2 Prius Main Forum' started by tom1l21, Nov 3, 2009.

  1. tom1l21

    tom1l21 Member

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    Currently, I am running on Goodyear integrity's which came with my Prius. I have added an additional 11k on top of whatever miles were previously added to the current set. The tires are very worn, in some spots, flush with the wear bars. I have been running them at 45f/43r psi. I am having a set of WR-G2's put on thursday. Because these tires are worn, they are probably fooling the computer into believing that I am traveling a further distance, thus displaying better MPG's than I probably am actually getting.

    When I put on my new WR-G2's, which I will run at the same pressure (is this ok pressure for these tires?), I will most likely see a decline in MPG's simply because the wheel radius is larger, correct?

    Since the WR-G2's are a LRR tire, will that be a wash with my current integrity's (not LRR) in terms of the impact of rolling resistance on my MPG's?
     
    #1 tom1l21, Nov 3, 2009
  2. F8L

    F8L Protecting Habitat & AG Lands

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    I doubt it will be a wash. I think you will still see a milage drop because of the compound/tread difference in the Nokian and the fact they are new and sticky. After 3,000 miles or so you may even back out.
     
    #2 F8L, Nov 3, 2009
  3. tom1l21

    tom1l21 Member

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    So initially I will be hit with both the losses from the larger radius as well as the new tread. I wonder what that will be, its so hard to get a definitive answer because of all the variables, but I'll try to get some results over the next 3k. I dont' have last years winter performance since I got my Prius in the Spring, but I'll see if I can interpolate or look for similiar temperature conditions.
     
    #3 tom1l21, Nov 4, 2009
  4. jdenenberg

    jdenenberg EE Professor

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    My WRg2s made good MPG from the start. Yes you do need to correct for the different revolutions/mile (the WRg2s are actually a little larger than the Integriy tires were when new 851/m vs 855/mile), but this effect is not a real change in MPG, just a change in the calibration of your ODO/MFD/Speedo.

    The "sticky" tread is a wives tale, don't believe it (Only affects MPG if tire alignment is off)

    The biggest improvement you will see with the Nokians is in cold weather. The rubber compound doesn't stiffen in the cold so the MPG (and traction) will be better than with the Integrity tires.

    I am on my fourth set of tires on my 2004 Prius at 161,500 miles.

    1. GY Integrity - Terrible tires, replaced at 44.5k miles
    2. Michelin MVX4+ "Energy Savers" - better tires, slightly better MPG, replaced after 55k miles (99.5k total)
    3. Nokian WR - Great tires, still better MPG and safe in winter weather, but a little noisy, Replaced after 48k miles - 147.4k total
    4. Nokian WRg2 - about same MPG as WRs, Quieter then WRs, but may not be quite as good in snow (no winter driving yet so we'll see)
    See the attached spreadsheet for details.

    JeffD
     

    Attached Files:

    #4 jdenenberg, Nov 5, 2009
  5. tom1l21

    tom1l21 Member

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    Jeff, thanks for the info. I can't look at the spreadaheet since its compressed and I'm replying from my BlackBerry. Is there a way to calibrate my Prius for different Rev/mi? Is there some setting that can be accessed on the MFD to do so?
     
    #5 tom1l21, Nov 5, 2009
  6. F8L

    F8L Protecting Habitat & AG Lands

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    My swap from Integritys to Nokian i3s took an inital hit and the i3 supposedly has a lower RR than the WRs. Milage seemed to have leveled out after break in though.
     
    #6 F8L, Nov 5, 2009
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