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Speedo calibration?

Discussion in '2nd Gen. Tacomas (2005-2015)' started by Jetman1979, May 9, 2013.

  1. May 9, 2013 at 8:57 AM
    #1
    Jetman1979

    Jetman1979 [OP] Well-Known Member

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    Drove my truck from Texas to California nice long ride. I noticed my speedo was off by 5 mph truck would say 85 mph and the gps showed 80. Running stock 245/75/16 tires. If I go up to 265s it wouuld get worse. Can the speedo we adjusted by the dealer with his computer?
    Pretty sure the Garmin is spot on because I used it as my speedo the whole trip and got no tickets.
     
  2. May 9, 2013 at 9:09 AM
    #2
    BamaToy1997

    BamaToy1997 Wheel Bearing Master

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    Some manufacturers can program specific tire sizes into the ABS computer, which in turn will adapt the speedometer. Although I have seen some GPSs notoriously inaccurate on speed. Best way is to use a stop watch, set cruise at 60 on a flat road, and time yourself between mile markers.
     
  3. May 9, 2013 at 10:34 AM
    #3
    spithead051

    spithead051 Well-Known Member

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    With your truck being a manual, I believe they put the speed sensor somewhere on the driveline, the end of the transmission I believe.

    Tire size changes won't have an affect on that and I believe the only way to "calibrate" our speedos is with an in-line corrector.

    I'm probably wrong somewhere so anyone can correct me :D
     
  4. May 9, 2013 at 1:36 PM
    #4
    sportsguy

    sportsguy searchgeek

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    Bustin' dreams... ;)

    Yesterday I installed 265/75/16 Duratracs on my otherwise stock 2011 reg. can 4x4, 5spd (with cupholders!).

    Before I went in, the speedo was generally a few mph optimistic at 60 mph, with the GPS suggesting I was 1 - 2 mph slower than the speedo suggested. That'd be about right with manufacturers setting things this way from the factory.

    Now, after the slightly larger tires, I'm close to 60 mph on the dash (just over) when the GPS says 60 mph.

    Getting up to 70 mph on my speedo and the GPR is telling me 74 in the real world now. This tracks with what tire size calculators suggested would happen.

    ...which smokes the theory of the speed sensor on the tranny feeding the speedo, methinks... :(

    That, or I'm totally confused, in which case I don't give a f*ck any more and will simply slow down to "retirement" speed... ;)
     
  5. May 9, 2013 at 2:36 PM
    #5
    moondeath

    moondeath Well-Known Member

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    I don't think there is a whole lot that can be done. Aside from buying different electronic devices to monitor your speed. As for going to a size 265, that won't change your speedo as that is the width of the tire. Perhaps you were meaning 265/75, then you would notice a big difference. Mine changed by 3.3% when changing my size. I just try go slower than what my speedo says.
     
  6. May 9, 2013 at 2:41 PM
    #6
    sportsguy

    sportsguy searchgeek

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    Actually, that width plays a role, unless you adjust the aspect ration. 70% of 265 is a different result than 75% of 265. If you overlay the actual tires, the actual differences may not appear to be much, but a speedo that's off by 3 - 4 mph will get you a ticket just as easily as one that's accurate with your lead foot prodding it along. Johnny Law cares not for our tire size related issues... ;)
     
  7. May 9, 2013 at 3:08 PM
    #7
    moondeath

    moondeath Well-Known Member

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    That's what I was getting at. Maybe what I said didn't sound right. The width alone won't change your speedo. The side wall percentage is the determining factor of what your speedo will display.
     
  8. May 9, 2013 at 3:26 PM
    #8
    gtrplr

    gtrplr Member

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    3" revtek front, 1.5 aal trailmaster rear, 265 70R16 Toyos, K&N filter, rubber between rear springs.
    Same exact tire size, same spedo/gps readings.
    Badass tires btw, better in snow than the toyo mt's although about 1/2"shorter. I got 72K miles out of the toyos though but they were scary bald at the end. But made me a better driver.
     
  9. May 9, 2013 at 6:21 PM
    #9
    BamaToy1997

    BamaToy1997 Wheel Bearing Master

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    The speedometer sensor for all 4WD Tacoma trucks is located at the output shaft of the transfer case. If it were at the transmission, then your speedometer would be VERY inaccurate when you put the transfer case into 4LOW.

    Tire size changes have a DIRECT effect on the speedometer, as it changes the rotational speed of the driveshaft.
     
  10. May 9, 2013 at 8:38 PM
    #10
    DueNorth

    DueNorth Well-Known Member

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    You can adjust your speedo from using larger tires or regearing...
    Simply buy a hypertech inline speedometer calibrator and all your problems go away ;)
     
  11. Apr 5, 2021 at 8:02 PM
    #11
    Phil61s

    Phil61s Well-Known Member

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    I just signed up on this site today, first off for this reason. I see this thread is 8yrs old, but maybe someone found more info?
    First mod after purchase was 265/75/16's, at 40 miles on odo. When I calculated fuel mileage after first tank, I thought it was a bit low (16mpg) But did get on the throttle a bit on the test drive, and some up-hills. But then remembered I had to swap-out the speedo gear on my 04 Jeep Wrangler, so figured would be the same issue here.
    The over-size tires is going throw off the odometer, and the on dash display reading real time fuel mileage.....any one? Just noticed I an in the "2nd gen" forum, this is 3rd gen.
     

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