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Anyone Know my actual Speedo reading??

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Boss, Jun 8, 2001.

  1. Boss

    Boss 1/2 ton status Author

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    I know after you put some larger tires under your speedo doesn't read right. I'm trying to figure out what my speedo is reading.
    36" tires. (35.5" is true reading)
    4.56 gears
    700R4 Tranny
    What how fast/slow am I really going at 65mph??

    I know this is the formula used to find it out, but only with stock gears.
    (New Tire Diameter / Old Tire Diameter) * Speedometer MPH = Actual MPH
    But my gears went from 3.42 to 4.56. Thanks for any help.
    I would think the gears are reading 5 mph too fast. That's my guess, so it reads 65mph, I'm actually goin 60mph (maybe).
    Boss


    <A target="_blank" HREF=http://www.boss.coloradok5.com>http://www.boss.coloradok5.com</A>
     
  2. rocko

    rocko 1/2 ton status

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    I've been wondering the same thing myself.. I went to 33 inch tires from 31's and from 3.08 gears to 3.73's..
    So I'm thinking I'm way off.. my truck says it's doing 60 and it feels like 'm going faster.. dunno.. guess I can have one of my cop friends clock me w/ their radar at 60 mph..and get a true reading...


    Experience is something you don't get until just after you need it. <A target="_blank" HREF=http://www.rocko.coloradok5.com>http://www.rocko.coloradok5.com</A>
     
  3. Boss

    Boss 1/2 ton status Author

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    Rocko,

    The wierd part is, when mine reads 75mph, I think I'm only going 65mph to 70mph. Usually, it's the other way around, but I think mine reads faster. I think I'll just follow a friend and ask him how fast he was going and figure it out then. Who knows.
    Boss

    <A target="_blank" HREF=http://www.boss.coloradok5.com>http://www.boss.coloradok5.com</A>
     
  4. newyorkin

    newyorkin 1 ton status

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    Did you guys try this speed calculator http://k5.8m.com What more is there to life?**
     
  5. Pugsley

    Pugsley 1/2 ton status

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  6. AMorris1

    AMorris1 Registered Member

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    The same formula would apply for gears as for tires. (new ratio/ old ratio) * speedometer = actual speed. For mine it worked out that 65mph reads as 77mph on my speedometer. I double checked it with my wife following me and a cell phone.
     
  7. rocko

    rocko 1/2 ton status

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    Great... thanks everyone...
    Boss.. my truck is weird period... lol.. sometimes things work.. sometimes they don't.. but I love her anyway !!!!!

    Experience is something you don't get until just after you need it. <A target="_blank" HREF=http://www.rocko.coloradok5.com>http://www.rocko.coloradok5.com</A>
     

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