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Finally Got Axles Back Under Her! Need Shackle Help! LONG!

Discussion in 'The Garage' started by Batmanjr, Jul 26, 2003.

  1. Batmanjr

    Batmanjr 1/2 ton status

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    Alright! Finally got the axles back under her after regearing and adding lockers front and rear.. While they were out, I put 52s up front and 63s in the rear.... The front looks SWEET! Sits very nicely and couldn't be happier! The rear sits Sweet also, but the rear shackle is FUBAR! I never moved the front hanger and now I have too... The rear hanger was moved back 6" and the rear shackle was replaced with an 8" one from Borrego! Now that the truck is sitting on them, the rear shackle is HORIZONTAL! The spring is hitting the center tube on the rear shackle... I know I can't run it this way, so what I need to know is How far to move the front hanger forward... The truck is sitting perfectly level right now, I really don't want to add too much lift to the rear... I have zero rates on the springs, so it looks like those are going to go... That will give me an inch to work with there, and I will probably add an inch more... Thus giving me 2 more inches to add by moving the front hanger forward..... Now for the big question.......... How far forward do I move the front hanger to move the rear hanger down two inches? I'm thinking in the 2-3" range.... But according to good ol Algebra, I would only need to move it .25"......... Here is a picture of what I'm talking about:
    [​IMG]

    And for reference, here are some pics of my current shackle situation:
    [​IMG]
    [​IMG]

    Thanks for all your help. I really apreciate it all! /forums/images/graemlins/thumb.gif
     
  2. 55Willy

    55Willy 3/4 ton status

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    heres my 2 cents...

    1) remove the zero rate, you'll need all the fudge factor you can get to work with.

    2) measure the spring right now eye to eye straight across, that is your loaded spring length. (unless the spring is actually resting on it then you have other probs)

    3) jack the truck up and remove the lower shackle bolt.

    4)swing the skackle forward til you get a 30* angle on it or so (others will post thier fav angle for a shackle)

    5) measure from the shackle eye forward your loaded spring length distance, thats where the new front bolt should go.

    6) move the mount to line up. bolt everything back up

    7) FLEX THE MUTHA OUT

    /forums/images/graemlins/smile.gif
     
  3. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    I like puzzles like this......but those red "x"s make it really tough....! /forums/images/graemlins/thumb.gif


    I think Jeremy has the right idea. The main problem is you can't just jack up the truck and reset the hanger....once you put weight back on the suspension all the measurements change!!!

    I like the idea of taking a "static loaded" measurement of the leafspring as it sits now. That is side "A" of your triangle. The next side of the triangle is the shackle (call that Side B) and the final side (Side C) is the imaginary line from the upper shackle bolt to the frontmost spring eye bolt.

    Once you get a meaurement for each of those three sides posted, I'm sure we can all double-check your math to make sure you only have to move those hangers ONCE! /forums/images/graemlins/rotfl.gif /forums/images/graemlins/thumb.gif
     
  4. Batmanjr

    Batmanjr 1/2 ton status

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    This should fix the problem!! Here are the pics, no more red x's! Sorry, but those are as big as they getr with webshots! /forums/images/graemlins/thumb.gif
     
  5. m j

    m j 1/2 ton status

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    if the wheel is centre'd in the wheelwell just move the rear hanger back a few inches

    can you post a link to the images? those are way to small to see what the issue is (found link in your sig)

    fab new hangers that are higher up
     
  6. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    OK,

    Now post up those measurements (Side A, B, & C) and we can start "doing the math".......


    /forums/images/graemlins/thumb.gif
     
  7. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Oh yuck.....

    m j's got a point there.....I forgot, one of the ugly things about moving the FRONT spring hanger is that your axle is going to be relocated also. Moving the REAR hanger would be wiser unless you have some specific limitations there.....



    /forums/images/graemlins/eek.gif
     
  8. BorregoK5

    BorregoK5 1/2 ton status

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    Your math was right on. Theoreticly, a 6" rear hanger relocation should have put you where you needed to be, but the loaded length of the spring and small tollereances here and there in the real world added up to a loss. Take a look below, each grid line equals 1". Value X equals the distance from the shackle hanger mount, value Y equals the resulting height. The blue curve reperesents the 8" shackle arc of travel. If we start with X as 8" (same as the shackle and close to what you have now) the the shackle would sit horizontal or zero degrees). Take 1" from X at this point and the 8" shackle arc of travel will pull Y to +4" (height) and a near 30 degrees of shackle angle as shown in RED above. Taking yet another inch from X yeilds half of the initial result as shown in purple due to the shackle arc. I think where your math is biting you is your assumption that your X is 8" as you sit now, gaining 2" in Y would only require 1/2 of loss on X to acheive this but would also result in a poor shackle angle.

    [​IMG]

    As stated above, springs are generally measured from eye to eye under load. But changing the load could in effect result in a loss of arch and effectively lengthen the spring. You can see from the chart above how 1" gain could take you from a 30 degree shackle angle to zero and a loss of 4" in height. I would suggest measuring the spring eye to eye under the amount of weight you intend to put on it, then measure the true length of the spring, along the spring (not horitontally eye to eye). Set your shackle angle to be 1" less then Horizontal with the springs TRUE flattened length so as never to over extend, and adjust the rear hanger height to give you your desired lift at the loaded length and resulting angle.
     
  9. Batmanjr

    Batmanjr 1/2 ton status

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    Alright,
    I would love to move the back hanger back more, but it's as back as it gets structurely! If I move it back ANY further(which I only have about and inch) I will be running into the large holes the factory put into the frame to run wires and the frame is a lot less structurely intact back there! Also, the axle is about 4" behind where it normally sits! There's no way to mount a 63" spring without moving the front hanger and have the tire in the center of the wheelwell... I've decided it is mandatory for me to move the front one to suck up some of this extraordinary length! I agree with the arch diagram and so forth with Borrego... If I read that right, Would I be safe to say that if I measured the leaf along the spring and used that as full stuff length and set that length to 1" below where I have it now, I would have the correct setup to limit stuffing and to make full use of droop.... THe measurements are as follows:
    A) distance from spring eye to spring eye: 64"
    B) distance from hanger eye to hanger eye: 6"
    C) distance from top hanger eye to front spring eye: 58.25"
    ....All measurements were taken from the center of the bolt right at the grease fitting!

    It looks to me like the spring is almost at full stuff, it can't get much longer! If it gets stuffed any higher, it's going to go into negative arch!
    Here is a link to all the photos of the suspension: Photos
    I'll be back on Sun. to read all this great input, thanks guys!
     

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