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Speedometer: How fast??

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BLzr4x4ngkid, May 8, 2000.

  1. BLzr4x4ngkid

    BLzr4x4ngkid 1/2 ton status

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    With 35's, about how much is the speedometer off?? I figured mine is off by about 7-15mph. I haven't had much time to check it. How much is your guy's speedo off?? HAHAHA Thanks again.



    Alex
    Wichita, KS
    What me get stuck? NEVER!!(Famous last words)
     
  2. Blazer79

    Blazer79 1/2 ton status

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    There's a calculator at http://www.4lo.com that helps you with that and other stuff.

    <font color=black>//////
    What the heck!...Drive it like gas is $0.50/gal!!!
    </font color=black>[​IMG]
     
  3. 70jimmy

    70jimmy 3/4 ton status Premium Member GMOTM Winner

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    On speedometer change with larger tires you need to realize that there is no specific amount that a speedo is off. As your speed increases you amount of error increases. You need to check it at different speeds. Easiest is of course 60 seconds at 60 mph to go one mile. Use a stop watch or second hand and the milemarkers. Also remember that if speedo is off so is your odometer. To figure out how long it should take at a given speed to go one mile use the following: Speed times 1.466 then take 5280 divided by answer and that will give you number of seconds to travel one mile. Example 75 mph times 1.466 =109.95 5280 divided by 109.95 =48.0218281 or just over 48 seconds. The 1.466 changes mph to feet per second and the 5280 is the number of feet in a mile. I will make it easy: 30mph = 120 seconds
    35 mph= 102.90 seconds
    40 mph =90 seconds
    60 mph = 60 seconds
    65 mph = 55.4 seconds
    70 mph = 51.45 seconds
    75 mph = 48.02 seconds
    80 mph and up = you dont need to know
    Once you know this you can put a little note on the dash as a reminder, Keeps you out of hot water with your signifigant other. All those who are worried about how fast you are going please raise your right foot.
     
  4. BLzr4x4ngkid

    BLzr4x4ngkid 1/2 ton status

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    I'm not too worried about the speed. I was just kind of curious. Basically, I don't care how fast I'm going as long as I get there safely without incident.

    Alex
    Wichita, KS
    What me get stuck? NEVER!!(Famous last words)
     
  5. CrazeeBush

    CrazeeBush 1/2 ton status

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    Would this work?

    Take a trip down the interstate and go say 10 miles, and record the miles on your odomenter, then use the actual vs. error to set up a ratio? Like I went 10 miles and odometer says 9.6.

    Then 10/9.6=(Actual MPH)/(My Speedo Reeding)

    Then do some cross multiplying and you get:

    9.6*(Actual Speed you wanna go, say 80 MPH)=10*x

    where x would be the value your speedo would say.

    I dunno, I'm just rambling off stuff... I think that would work. Someone correct me if I'm wrong... That ould give you a percentage of error that would increase with speed.
     
  6. walrus101

    walrus101 Registered Member

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    easiest way to get a good guess is when you are driving down the highway look at the mile markers as you go by. look at your odometer and compare. for every 10 mi. my odometer is off .5mi so every 20 i am off 1mi. so at 20mph i am doing 21 at 40 doing 42 and so on. this is not completely accurate but it gives you an idea. plus it gives you something to do while you are driving.

    walrus101

    goo goo gaju
     
  7. Zack

    Zack 1/2 ton status

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    Actually the easiest way to do this is to find a cop on patrol or just sitting in his car and ask them nicely and tell them that you just put larger tires on and you would like them to radar you to see how fast you are going and then drive by when yours says 55 and then go back and see how fast the actual speed was.


    <font color=red>Zack Carlson</font color=red>
    <font color=yellow>Carlson@thestix.net</font color=yellow>
     

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