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Must leaf springs be parallel?

Discussion in 'The Hokey Ass Message Board' started by creeder, Apr 1, 2011.

  1. creeder
    Joined: Mar 23, 2005
    Posts: 29

    from Pa

    I need about 1/2" to fit larger tires on my Falcon. If I use an offset 1" shackle, will it cause problems. I was going to move the front in also, but if I don't have to it would save alot of work. And if they can be unparallel, how much is too much?
  2. gnichols
    Joined: Mar 6, 2008
    Posts: 10,969

    from Tampa, FL

    Most aren't. Gary
  3. They don't have to be parallel BUT you can't just use an offset shackle in the rear without angling the front pivot or you will have massive bind in the bushing.
  4. slickhale
    Joined: Dec 19, 2010
    Posts: 770

    from Phoenix

    look under an '88-98 chevy truck, those things are like 3" closer at the back, you'll be fine with an offset shackle

  5. borntowrench
    Joined: Jan 7, 2009
    Posts: 28


    They must run parallel. As the spring flexes, the distance between the front fixed mount and the point where the axle mounts increases slightly (the spring is getting flatter). If the springs aren't parallel the distance between the axle mounts would want to change also, creating a bind situation.
  6. Ricci32
    Joined: Jul 30, 2010
    Posts: 416


    When we ran leaf springs in a race car the springs were always narrower in the front the whole chassis was tapered.
  7. With rubber bushings, no problem.
  8. 117harv
    Joined: Nov 12, 2009
    Posts: 6,590


    x 2.
  9. The_Forgotten
    Joined: May 6, 2009
    Posts: 83

    from WNY

    As long as the front and rear mounts are at the same angle, you can mount them at whatever angle you need. You can't, however, just kick out the front or back since the un-changed mount would bind.

    I'm using triangulated quarters on my current build (note, this picture is from the net from a '20 Chevy race car, not of my project.) Just to show you what I mean.

    Attached Files:

  10. storm king
    Joined: Oct 16, 2007
    Posts: 1,991

    storm king

    Most Mopars are not parallel. There's lots of good info in the Mopar Chassis Manual, available from many sources, Mancinni, and I'm sure Amazon, that will help anyone working with leafs, and wants a performance suspension.
  11. badshifter
    Joined: Apr 28, 2006
    Posts: 3,329


    Better not let the OEM's know that the billion cars and trucks out there with non-parallel leafs are in a bind.

    Yes, as answered you can run them non-parallel and the small offset you plan on should be more than absorbed by the bushing.
  12. stealthcruiser
    Joined: Dec 24, 2002
    Posts: 3,748


    What he said!!!!
  13. I went through this with my pickup.I bought a Posie's rear parallel leaf setup and it is 6 inches narrower in the front than the rear.Posie assured me this is the way it is designed.As long as you don't bind the mounts like previously stated.
  14. Engine man
    Joined: Jan 30, 2011
    Posts: 3,476

    Engine man
    from Wisconsin

    No problem as long as you have rubber bushings. The axle moves sideways in corners and doesn't bind. You could elongate a hole at the front mount if you are worried about it.
  15. X8, ditto, our race car springs were not parallel, my quarter elliptics are not.
  16. Mr48chev
    Joined: Dec 28, 2007
    Posts: 29,048


    He nailed it. as long as the mounts and shackles are lined up square with each other you are good to go. If you just swing the rear of the spring in 1/2 inch you will put the bushings in a bind and wear them out rather quickly along with creating other problems.
  17. creeder
    Joined: Mar 23, 2005
    Posts: 29

    from Pa

    I will just move the front in also so it is correct. Thanks for all the input.

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