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Technical Ladder bar travel question

Discussion in 'Traditional Hot Rods' started by Ratspit, Aug 4, 2019.

  1. Ratspit
    Joined: Dec 6, 2017
    Posts: 287

    Ratspit
    Member

    I just got my perimeter frame done for my 34 pickup and jumped right in to mocking up a few things up. The frame has been pinched, kicked, and sectioned. First up was the quick change and ladder bar setup. My question is how much travel can I expect on the 48" ladder bars? Maybe the better question is how much spring travel can I expect with the "A" spring? The back end of this truck should be light. I figured 3" of travel at the axle equates to about 1.25" travel on the ladder bar where I have a clearance issue. As you can see from the pictures, I sectioned the frame so the floor will actually sits 2" lower. With a little work I should be able to get 2" of clearance but is that enough? 20190801_103333_resized.jpg 20190801_132246_resized.jpg
     
  2. s55mercury66
    Joined: Jul 6, 2009
    Posts: 4,335

    s55mercury66
    Member
    from SW Wyoming

    It looks like your frame is sitting on the axle, and that will definitely be the limit of your suspension travel.
     
  3. The bars will go into the plane of the floor if you set the bars up correctly. Just make the floor go up and over the bars. The top bar should be at least relatively parallel with the ground.
    That frame sets far far far below the rear axle centerline.

    3” travel is good. The amount your spring moves is going to vary
     
  4. DDDenny
    Joined: Feb 6, 2015
    Posts: 19,144

    DDDenny
    Member
    from oregon

    The reinforced ends on your bars are quite different, any chance of some closeup shots.
    I like them, are they machined or welded and detailed?
     

  5. That looks like “est 1946” stuff.
    I had some bad experience that left a bad taste
     
  6. Tim
    Joined: Mar 2, 2001
    Posts: 17,098

    Tim
    Member
    from KCMO

    If you jumped that thing dukes of hazard style you might get 3 inches on landing. If it clears until 3” I’d say your likely fine. Just don’t mount brake lines or anything where it’s gonna crush if it does hit at some point.

    These cross spring set ups don’t move a whole lot but I’d assumed 2” is cutting it close
     
  7. HotRod33
    Joined: Oct 5, 2008
    Posts: 2,570

    HotRod33
    Member

    If you're bars going to mount where they are right now your clearance sound be okay..... your suspension travel is maxed out as you rear axle has the frame sitting on it
     
  8. HotRod33
    Joined: Oct 5, 2008
    Posts: 2,570

    HotRod33
    Member

  9. HotRod33
    Joined: Oct 5, 2008
    Posts: 2,570

    HotRod33
    Member

    My setup has 4 inches of travel on the rearend ... But that doesn't mean it will move that much
     
  10. lostone
    Joined: Oct 13, 2013
    Posts: 2,820

    lostone
    Member
    from kansas

    When I build systems like this for customers I follow these guidelines.

    1_ I put the frame at ride height where I want it to sit when the car is finished.

    2_ I put the suspension under the frame and decide on tire heights. Once tire heights are known I set the rear end at half height minus about an inch for side wall flex, example: 30" tall tire I set the housing center at 14" to 14 1/2" from floor.

    3_ build rear suspension to that height, my lower bars are always parallel to the ground be it ladder bars or 4 link.

    4_ now I worry about springs, coil overs etc. Leaf springs I build to what I want, coil overs I just buy some to fit my needs.

    This way I always end up with a vehicle sitting exactly where I want it and not fighting or trying to figure out how to get a car to desired height once it's together.
     
    31Vicky with a hemi likes this.
  11. Ratspit
    Joined: Dec 6, 2017
    Posts: 287

    Ratspit
    Member

    Yes the bars are from SoCal. I think the ends are forged. 20190804_204639_resized.jpg
     
  12. Ratspit
    Joined: Dec 6, 2017
    Posts: 287

    Ratspit
    Member

    Right now I set a block under the frame just in front of the rear wheels. That has the frame at 6.5" off the ground. I put 2 degrees of rake in the frame for now. The rear axle has 2" of travel in this configuration. I can "C" notch the frame if necessary or raise the ride height. 20190804_204507_resized.jpg 20190804_204559_resized.jpg Once I get the cab back from being dipped I can chop and channel. then It should be easier to finalize ride height and rake. I just wanted to do a rough layout and find any glaring issues. The ladder bars posed the most obvious issue to start thinking about.

    Thank you for the Pete & Jakes info.
     
  13. rooman
    Joined: Sep 20, 2006
    Posts: 4,045

    rooman
    Member

    Figuring the clearance is pretty simple. If the rear end travel is 3", at the midway point on the ladder bar you will need 1.5". One third of the way back from the front pivot it will be 1" and two thirds of the way back 2". These numbers are based on the ladder bar being basically parallel to the ground but are close enough even if the bar runs up or down relative to the ground plane.

    Roo
     

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