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Speedometer calibration?

Discussion in 'CJ' started by 5oakseric, Dec 12, 2017.

  1. Dec 12, 2017 at 8:07 PM
    #1
    5oakseric

    #1
    5oakseric [OP] Member

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    I'm still figuring out what I've got with this CJ. Today I found out the speedo is wrong. It reads 63 when I'm going 70. No big deal but... I'm just curious why and how I can make it correct. I know tire size makes a difference but Its got 235s on it. Not huge tires. I want to put 31/10.5 15"s on it. Is there a way to calibrate the speedometer?
    I took your advice OFFGRID and ordered a HEI distributor (DUI) and a new set of wires. Between that and the Weber carb I hope to have it running a lot better soon.
     
    Last edited: Dec 13, 2017
    5oakseric, Dec 12, 2017
    #1
    JKBob 25 likes this.
  2. Dec 13, 2017 at 5:57 AM
    #2
    OFFGRID

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    OFFGRID Well-Known Member

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    Howell fuel injection, header, HEI distributor, TH350, NP208, SOA lift with YJ springs in the front & GW springs in the Rear. AMC20 with G2 1 piece chromos trussed, Dana 30 with G2 chromos and 760x ujoints and MM Stainless Hubs, Geared 4.56. Tom Woods shafts, Metal cloaks, Caged, 37" Toyo MTs.
    What is the whole number of your tire size? 235/??r?
     
    OFFGRID, Dec 13, 2017
    #2
    JKBob 25 likes this.
  3. Dec 13, 2017 at 6:00 AM
    #3
    5oakseric

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    5oakseric [OP] Member

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    235/75R 15
     
    5oakseric, Dec 13, 2017
    #3
  4. Dec 13, 2017 at 6:11 AM
    #4
    OFFGRID

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    OFFGRID Well-Known Member

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    Howell fuel injection, header, HEI distributor, TH350, NP208, SOA lift with YJ springs in the front & GW springs in the Rear. AMC20 with G2 1 piece chromos trussed, Dana 30 with G2 chromos and 760x ujoints and MM Stainless Hubs, Geared 4.56. Tom Woods shafts, Metal cloaks, Caged, 37" Toyo MTs.
    28.8 (29) inches tall, 9.25 inches wide, on 15 in wheel. The 31 inch tires you plan on installing should get your speedo pretty close to correct.
     
    OFFGRID, Dec 13, 2017
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    JKBob 25 and chris4x4 like this.
  5. Dec 13, 2017 at 10:38 AM
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    2oldjeeps

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    2oldjeeps Well-Known Member

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    98 lifted, 00 stock 99wj just beautiful
    sounds like he will go faster? bigger tires yet?
    am i wrong?
     
    2oldjeeps, Dec 13, 2017
    #5
  6. Dec 13, 2017 at 12:15 PM
    #6
    OFFGRID

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    OFFGRID Well-Known Member

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    Oh yes you are correct. My brain slipped. Once you have the larger tires on call quadratech they are good with helping you choose the right speedo gear you need.
     
    OFFGRID, Dec 13, 2017
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    JKBob 25 and aggrex like this.
  7. Dec 13, 2017 at 3:16 PM
    #7
    Prerunner1982

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    Prerunner1982 Well-Known Member

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    I would measure your 31s. I have owned a number of sets of 30"s and they all measure 28.5". I am sure the guy that decided to market them as 30" tires was probably the same guy that told girls he was 8"... fudge a few inches here and there and nobody will notice.

    As much as I hate metric size tires they seem more true to size, or at least the few sets I have had have been. My 245/75/16 tires were right at 30.5".
     
    Prerunner1982, Dec 13, 2017
    #7
    OFFGRID likes this.
  8. Dec 15, 2017 at 10:43 AM
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    GR1ND3R

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    GR1ND3R Member

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    GR1ND3R, Dec 15, 2017
    #8
    5oakseric[OP] likes this.
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