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Thread: 07 F-150 5.4 Auto Speedo/Tire Recalibration

  1. 10-15-2007 #1
    86LT1MCSS
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    07 F-150 5.4 Auto Speedo/Tire Recalibration

    What is the correct way to calibrate the speedo and scale the shift points for 305 45 22 tires?
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  2. 10-16-2007 #2
    86LT1MCSS
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    OK after doing some math it looks like to me that the value I need to put for tire revs per mile is slightly larger than is allowed in that value.
    A 305/45-22 tire has 103.07 inches of rollout and there is 63360 inches in a mile.That comes to 614.72 tire revs per mile which is larger than the 559.23 that I can put in that cell.
    Also the stock tire revs per mile value is 424.4.If I do the math backwards 63360 divided by 424.4 is 149.29.The stock tire that came on this truck can't have 149 inches of rollout.
    What am I missing???
    Last edited by 86LT1MCSS; 10-16-2007 at 01:02 PM.
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  3. 10-24-2007 #3
    86LT1MCSS
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    BUMP
    Cmon people no one is changing speedo calibrations on these!!!!
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