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  1. #1
    Member StoreKeeper99Z28's Avatar
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    Pacific Beach //San Diego,Ca,U
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    White with Black Top
    1999/ Z28

    Question Speedometer Change

    I had 4:10 installed on my M6 Z28 Camero and the Tire size was then 275x35x18 they changed my computer to the new gears.

    I now put on New Rims and Tires ( 255x45ZRX17)

    My question is how much is my speedometer off since I went to the the Rim and Tire size?


    Any input would be greatly appreciated

    Thanks in advance

    Bruce/StoreKeeper99Z28
    __________________
    99Z28/M6/ Pro 5 and Lou's "Short Stick"/ AAP Custom Y Pipe 3"/ 4:10 Gears CMS/MMS Aggressor Cam 233/233/578/578/113 lsa/Mac Mid-Lenth Headers/Don lee Auto Ported Throttle Body and Ported LS6 Oil Pump/AAP 6.0L Heads/SLP Dual Cam Roller Chain/MMS Mike Morgan e-Tune,Dyno Tuning.

    Dyno: Sept 9,2007

    439 RWHP/398 Torque

  2. #2
    Junior Member
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    Apr 2008
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    Orlando, FL
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    2000 Z28

    http://www.1010tires.com/TireSizeCal...mp;vehicle=yes

    Let me know if that link works. If you put in your old tire/wheel size and new tire/wheel size, it will tell you the difference.

  3. #3
    Member StoreKeeper99Z28's Avatar
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    White with Black Top
    1999/ Z28

    Stock Tire - 275/35R18 >Search Tires Tire 1 - 255/45R17 >Search Tires
    Section Width: 10.82 in 275 mm Section Width: 10.03 in 255 mm

    Rim Diameter: 18 in 457.2 mm Rim Diameter: 17 in 431.8 mm

    Rim Width Range: 9 - 11 in Rim Width Range: 8 - 9.5 in

    Overall Diameter: 25.57 in 649.47 mm Overall Diameter: 26.03 in 661.16 mm

    Sidewall Height: 3.78 in 96.012 mm Sidewall Height: 4.51 in 114.55 mm

    Radius: 12.78 in 324.61 mm Radius: 13.01 in 330.45 mm

    Circumference: 80.33 in 2040.3 mm Circumference: 81.77 in 2076.9 mm

    Revs per Mile: 813.4 Revs per Mile: 799.0

    Actual Speed: 60 mph 100 km/h Speedometer1: 58.9 mph 98.2 km/h

    Speedometer Difference: - Speedometer Difference: 1.802% too slow
    Diameter Difference: - Diameter Difference: 1.77%

  4. #4
    Junior Member
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    2000 Z28

    So your speedo is like 1.1mph off. Not even worth getting calibrated.

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