Speedometer Is Out of Sync

Discussion in 'Lifted & Offroad Suspension' started by moosetags, Aug 13, 2009.

  1. moosetags

    moosetags Rockstar 100 Posts

    I recently upsized the tires on my '04 Suburban 2500. I went from the stock 245's to 265's. This increased the circumference by about 1.5" to 31". This change put my speedometer/odometer off by about 5%. At 70mph on the GPS, my speedo is showing 67mph. I have also done a couple of measured miles on the highway, and the odometer is also shy by about 5%.

    I have been to the GMC dealer twice and asked the to make the proper adjustment. They said that it was done, but the speedo is still off.

    Are there any suggestions out there as I am about ready to go to 265's on my '05 Yuk XL 2500.

    Thanx.
     
  2. willbradfan

    willbradfan Rockstar 100 Posts

    I am not sure if you can really do much other than getting the computer adjusted for the right tire size. I have 285s on my suburban and I have gotten my computer adjusted to the tire size and the speedometer is exact until i start going past 50mph, once i get past that there tends to be a 3-4mph difference in actual speed.
     
  3. azdrtdog

    azdrtdog Epic Member 5+ Years 100 Posts

    Ya i had mine calibrated for 35's and mine has a sweet spot also past 65 on gps it starts to lose track and get behind by a couple i think its the syntrifical force thing as the tires grow DONT know that for sure just one of many guesses
     

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