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Thread: speedo still off?

  1. #1

    speedo still off?

    hey after putting my 4.10's and going to a 255/50/17 my speedo was obviously off. so i disabled that vdc thing, changed the ratio to 4.10 and changed the rev's per mile to match my new tire size and my speedo is still off by about 5mph, any ideas?

  2. #2
    Senior Tuner
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    Hmmm, are you positive you got a set of 4.10s in the rear, and not say some 3.90s or 4.30s (depending on which way it's off)?

    Post up your stock tune and your current tune, bud.
    Formerly known as RWTD

    Toys: '22 Tesla Model S Plaid / '20 Chevy Duramax / ?20 Sea-Doo RXT-X (2)

  3. #3
    Senior Tuner edcmat-l1's Avatar
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    Quote Originally Posted by 02GTP View Post
    hey after putting my 4.10's and going to a 255/50/17 my speedo was obviously off. so i disabled that vdc thing, changed the ratio to 4.10 and changed the rev's per mile to match my new tire size and my speedo is still off by about 5mph, any ideas?
    Same problem here.

    Edit: Disabled VID, set gears to 4.10, and set the tire revs back to stock. Now it's dead nuts on.
    Last edited by edcmat-l1; 07-22-2009 at 10:54 AM.

  4. #4
    i think i figured it out. my tire calculates to a 27.0X inch. but i run 26 to 28psi for better traction and today i measured it with a tape measure and it was barely 26.5 so i will correct it for the new measured size and i think that should do the trick.

  5. #5
    Senior Tuner
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    Hmmm, what tire are you running, bud? When moving your tires will "grow", keep in mind.
    Formerly known as RWTD

    Toys: '22 Tesla Model S Plaid / '20 Chevy Duramax / ?20 Sea-Doo RXT-X (2)

  6. #6
    im running 255/50/17 Fuzion ZRi's. n like i said i run about 26psi becuase thats where they grip the best. ill re calculate it and go try it and let u know if it works.

  7. #7
    i recalculated the rev per mile to 761 instead of 742 and the speedo is spot on.