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Caster Question?

Discussion in 'Intermediate CJ-5/6/7/8' started by 1974Sixer, May 7, 2017.

  1. May 7, 2017
    1974Sixer

    1974Sixer Member

    Eureka, Tx
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    IMG_2089.JPG I need advice on what to do next. First off here's where I'm at, 1974 CJ 6. I just replaced the upper and lower ball joints, new wheel bearings on both sides, all tie rod ends and a new drag link along with a remanufactured manual steering box with a Borgenson u-joint steering shaft. New BDS springs with 2 and 1/2" lift as well.

    My problem is it wants to jump around on me when on the less than perfect country roads around here. Everything is tight but it just sort of has a mind of it's own on were it wants to go.

    I just got it aligned and my numbers show 2.04 and 2.13 degrees. I'm not sure how to interprete the numbers and what to do next. Spring shims? If so what degree?

    I've uploaded my alignment print out. Also, it appears my bottom ball joint is out ahead of my top ball joint. Is that normal? It's a factory spring under axle setup.
     
  2. May 7, 2017
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    What about the toe-in? That's the red measurement. There should be some toe-in. I'd puit the toe to the middle of the range.

    Pretty sure these numbers are in the TSM. As I recall, 2 degrees caster is within the factory spec, but typically you run like 4-6 degrees with lift springs.

    A solid rear axle doesn't have a camber or toe-in adjustment, so that goves you an idea of the precision of the measurement. Possibly that's how it can say the toe is ok and still come up red - rounded off it's zero but the measurement is actually slightly negative.
     
  3. May 7, 2017
    Dave B

    Dave B Frankenjeep '67

    Northern Minnesota
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    I don't have the answers, just the questions--others will chime in. Does "jump around" mean "wander left to/or right erratically/unpredictably" and is "a mind of its own" emphasizing the same problem?

    It will be helpful to know what tires you are running---bias or radial, size, type, etc.

    I run slight front toe-in even with radials.
     
  4. May 7, 2017
    Patrick

    Patrick Super Moderator Staff Member

    Los Alamos, NM
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    With manual steering I'd run 5-7 degrees caster.
     
  5. May 7, 2017
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
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    "Jump around?" Like Death-Wobble, an uncontrollable shaking?

    No point to considering anything else until you get some toe-in on it. That will bias the tires to self-center. Without it, they may be hunting left and right, and getting into a self-reinforcing harmonic. =Death-wobble.

    Tire balance can be a big factor too. Shocks also.
     
  6. May 7, 2017
    1974Sixer

    1974Sixer Member

    Eureka, Tx
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    I have 31 inch radial tires on it that were recently balanced and rotated.

    Tim, I'm not sure why they set the toe there. I would if I should take it back and say readjust to a 1/8th toe in?

    No death wobble, more like dart off to one direction or the other. It also doesn't return to center after a turn like it use to before I replaced everything.

    If I were to order shims would I want 4 degree shims to get a 6 degree caster? I'm confused if the 2 degrees I have now are negative?
     
  7. May 7, 2017
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
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    Toe in.
    Take it back, make 'em do it right.
     
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  8. May 7, 2017
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Yep, I would take it back and ask them to put the toe in the middle of the range. Easy.

    Re the caster, you probably had more caster before you installed the BDS springs. This matches my experience with the BDS springs. Yes, you have 2 degrees now - if you add a 4 degree shim you should have about 6 degrees positive. My local tire store offered to measure the caster again after adding some of Mike's shims - I have not taken them up on the offer ... yet.
     
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  9. May 8, 2017
    1974Sixer

    1974Sixer Member

    Eureka, Tx
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    I'll take it back.

    Ok, just to make sure I've got this. It appears to me that the bottom ball joint is closer to the front of the jeep than the top ball joint. Which is what I suppose is the 2° measturement. It appears to me that if I add the 4° shim with the thick part of the shim wedge towards the back of the jeep, I will bring the upper ball joint back and the lower ball joint forward. So my thinking is, I will be back to 2° but in the opposite direction.

    What is positive and what is negative? I want my top ball joint ahead of my lower right? 6° ahead to be precise for a 6° positive caster?

    Sorry if I'm repeating the same question but I'm having trouble understanding this.
     
  10. May 8, 2017
    supertrooper

    supertrooper Member

    moreno valley, ca
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    you want the thicker part of the shim facing forward for positive caster.
    [​IMG]
     
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  11. May 8, 2017
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
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    Think of the forks on a motorcycle or bicycle (or for that matter the casters on a grocery cart)- you want the patch of tire contacting the road to be behind where an imaginary line continuing down the forks would hit the surface of the road.

    How far behind is measured in degrees of offset that the forks/imaginary line depart from vertical.

    So I'd say your lower ball joint should look a little bit closer to the front of the jeep.

    H.
     
  12. May 8, 2017
    1974Sixer

    1974Sixer Member

    Eureka, Tx
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    Thank you guys...I got it now. For some reason I thought I needed the top ball joint out ahead of the lower. ( I was literally thinking of a shopping cart caster but I wasn't computing the lines like in the above diagram.)

    I'll order a 4° shim wedge and apply it with the think part facing the front of the jeep.

    Any opinions on the best/safest wedge to get?
     
  13. May 8, 2017
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
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    Honestly I think you're way too stuck on the caster- get your toe in set properly, take it for a drive see if you still have issues.

    If so then it's time to start thinking about shims.

    If not- enjoy the drive. :)

    H.
     
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  14. May 8, 2017
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    Extreme positive caster -

    [​IMG]
     
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  15. May 8, 2017
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
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    OK Tim, now post a pic showing extreme negative caster :D

    H.
     
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  16. May 8, 2017
    jzeber

    jzeber Well-Known Member 2022 Sponsor

    Morgan Hill, Ca
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    I am playing with this right now on my 71'. I replaced the D27 with a narrow track D30. Mine was doing the exact same thing. The toe was way too much and is now about 1/8". It helped but my caster is between 0 & 1 degrees. From what I have been told you want between 3-5 degrees positive. I am looking at a 4 degree shim, made of steel (forget aluminum) from Rubicon Express.
     
  17. May 8, 2017
    supertrooper

    supertrooper Member

    moreno valley, ca
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    get the shims from mcruff on this forum.
     
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  18. May 8, 2017
    1974Sixer

    1974Sixer Member

    Eureka, Tx
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    Is Mike and Mcruff the same person?
     
  19. May 8, 2017
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Yes. My shims are installed, I just have not been back to the tire store.

    Mike's work is exemplary.
     
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  20. May 8, 2017
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Yeah, but is it any good? :rofl:
     
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