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Speedo off due to larger tires and gas milage

Discussion in '2nd Gen. Tacomas (2005-2015)' started by Carlo, Mar 4, 2011.

  1. Mar 4, 2011 at 7:39 AM
    #1
    Carlo

    Carlo [OP] Well-Known Member

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    So, I calculate my milage and get pissed off all the time because I get about 14 to 15 in town and 17 on the highway. But, I just started to think that maybe my change in tires from the stock 245's to 265/75/16's may be effecting my milage calculation. I figured out the my speedo is off about 4% so does that mean that I am actually getting about 4% more miles to the gallon? Not that it's that much difference, but, around town I am only getting about 250 miles to a tank.
     
  2. Mar 4, 2011 at 7:44 AM
    #2
    snowgod06

    snowgod06 UG legend wannabe

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    You correct. I had to increase to 8-9.x% for mine(dont really remember). I get about 275 tank with my 33's. If you have the money you could get an ultragauge or scangauge and input the % difference and track your MPG.
     
  3. Mar 4, 2011 at 8:31 AM
    #3
    Bama_TACO

    Bama_TACO ROLL TIDE!!!!!!!

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  4. Mar 4, 2011 at 8:45 AM
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    tacoman007

    tacoman007 ignorance is bliss,

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    i bought a hypertech to fix the tire size problem. really easy to install
     
  5. Mar 4, 2011 at 8:50 AM
    #5
    05Moose

    05Moose Middle-Aged Member

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    First of all, separate your thinking from the speedo and odo. The speedo was off before you switched. It read about 4% fast with the stock tires and should be accurate with your new tire size.

    The odo is another matter. It was accurate before and with the new size will now read about 4% slow (3.9% according to the above post). So you need to multiply your miles by 1.039 to get your true miles, then divide that by the gallons to get your actual MPG.
     
  6. Mar 4, 2011 at 9:42 AM
    #6
    skytower

    skytower Well-Known Member

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    Dealer can change the tire size settings with the scan tool. Usually 1hr labor.
     
  7. Mar 4, 2011 at 9:43 AM
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    Marioso

    Marioso El Pitufo

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    chris4x4 once told me, for 33s you have to multiply your speedometer by .0743 in order to get the correct mileage
     
  8. Mar 4, 2011 at 9:49 AM
    #8
    macgyver

    macgyver Well-Known Member

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    The miata.net one posted above is a good calculator. I think it has been around since the beginning of the interwebz.

    According to that site, I'm off 6.9% going from 265/70/16 to 285/70/17's.

    I guess I should slow down a little bit then...
     
  9. Mar 4, 2011 at 10:01 AM
    #9
    Toyota Truck

    Toyota Truck Well-Known Member

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    I heard that the dealer can reflash your ECU to correct your speedo. Try using www.fuelly.com to track your MPG.
     
  10. Mar 4, 2011 at 10:07 AM
    #10
    jhodge83

    jhodge83 Any dog under 50# is a cat and cats are useless... Moderator

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    wat?
    multiplying speedo to get your mileage makes no sense...
     
  11. Mar 4, 2011 at 10:12 AM
    #11
    T@co_Pr3runn3r

    T@co_Pr3runn3r XXXXXXXXXXXXXXXXXXX

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    Neither does speedo being correct but odometer being off.
     
  12. Mar 4, 2011 at 10:14 AM
    #12
    jhodge83

    jhodge83 Any dog under 50# is a cat and cats are useless... Moderator

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    wat?
    that has to do w/ the digital/analog conversion....

    stock, the ODO will be correct and the speedo will be off. it's been covered in other threads.
     
  13. Mar 4, 2011 at 10:19 AM
    #13
    Superx2

    Superx2 Well-Known Member

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    If that's the case, then why am I getting 14.5 or less with my stock tires. This tank im on, I have kept it under 2500rpms. I will fill it up and see. I hear all these tacomas kicking my ass with the fuel mileage they are getting... im jealous.
     
  14. Mar 4, 2011 at 10:21 AM
    #14
    jhodge83

    jhodge83 Any dog under 50# is a cat and cats are useless... Moderator

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    wat?
    2k rpms is the magic number on the 4.0 autos
     
  15. Mar 4, 2011 at 7:40 PM
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    Superx2

    Superx2 Well-Known Member

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    so i filled my tank up after work tonight and did the mileage. 14.6 wtf? my wife thinks its great. that is using 89, average temp was prolly 35 degrees. guess it is what it is.
     
  16. Mar 4, 2011 at 7:46 PM
    #16
    jhodge83

    jhodge83 Any dog under 50# is a cat and cats are useless... Moderator

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    wat?
    i get better than that on 35s
     
  17. Mar 5, 2011 at 8:41 AM
    #17
    05Moose

    05Moose Middle-Aged Member

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    I'd say something is wrong then. Is it all highway miles or short trips. If short trips, I can see it happening in the cold. I've been driving all week to a training class that's 60 miles each way. A lot of stop and go on the freeway in the mornings. I've been getting anywhere from 20 to just over 21 mpg...and that's running 265/70-16 Michelin LTX AT2 tires. Wider than stock for an SR5. Now if I travel just 20 miles to the bus, then I get around 18 mpg. Big difference on the short trips.
     
  18. Mar 5, 2011 at 8:49 AM
    #18
    David K

    David K Well-Known Member

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    I would like to hear how the odometer and speedometer are not connected...

    If you travel 60 MPH on your speedometer (that is reading true per your GPS with the 32" tires [265/75-16]) then in exactly one hour your odometer should read 60.0 miles... yes???
     
  19. Mar 5, 2011 at 9:52 AM
    #19
    jhodge83

    jhodge83 Any dog under 50# is a cat and cats are useless... Moderator

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    wat?
    no. the easiest way to test this is to clear a trip meter while stopped with the nose of your truck at a mile marker, then drive to the next mile marker with your nose stopping at the same point. your ODO wioll read slightly slower. it can be better seen through a SG2 or UG as it will break it down into the hundredths of a mile.

    the ODO is spot on, but because of the digital to analog conversion to the speedo, that's why it's off. they are on seperate feeds. one goes digital to digital to the ODO, the other goes digital to analog to the speedo. anyone knows that if you put on a larger tire, the ODO and speedo will read slower if there hasnt been a recalibration to correct the size difference.
     
  20. Mar 5, 2011 at 10:08 PM
    #20
    David K

    David K Well-Known Member

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    So Toyota on purpose fixes the speedometer to read too fast with 265/70-16 (31") tires... but the odometer is spot on. Is there some adjustment for each model that has different size tires so they all have perfect odometers?

    Now, with the new 265/75-16 (32") tires my speedometer is spot on... but you say the odometer will read slower than the speedometer because they are not connected? If they are not connected, what turns the odometer if not the speedometer/ tires/ transmission???

    Any easy fix if I want the odometer to be as good as the speedometer with accuracy?


    Thank you!
     
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