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Hot Rods Question about mounting rear shocks

Discussion in 'The Hokey Ass Message Board' started by Devin, Jun 26, 2016.

  1. Devin
    Joined: Dec 28, 2004
    Posts: 2,352

    Devin
    Member
    from Napa, CA

    I was getting ready to mount shocks in the rear this afternoon and during mockup, I came to the realization that my original game plan my not be ideal. My plan was to mount the shocks at a slight angle with the tops running towards the center. The bottom mounts are well outboard which is good, but in order to clear the other suspension components, I have to lean them in at a 30* angle. My suspension is adjustable, so my concern is that there may be some bind throughout the entire range of travel. The shocks I am using are Afcos with the heim style bearing ends so they can accept a fair amount of misalignment. I will never lay frame with my setup, so I plan on dropping only 2-3" below ride height and raising another 3-4" to clear obstacles so max 7-8" of travel. The shocks have 9" of range, so all should be good. I've noticed that some mount their shocks vertically with the shock mounting bolts running parallel to the axles. If I mounted the shocks in this fashion, I could achieve a more vertical shock angle however they would be mounted significantly more inboard than the current scenario. Attached are a couple photos pulled off the web (not my car) to help visualize what I'm talking about. Am I over thinking this? Any advice is greatly appreciated.
     

    Attached Files:

  2. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,284

    Kerrynzl
    Member

    Don't do them as in photo 1
    moving shocks inboard and laying them over will compromise any dampening during body roll.
    [It has almost the same effect as mounting 1 shock on the centre off the rear end.]
    Mount them as far apart as possible on the rear end
     
  3. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 8,344

    mgtstumpy
    Member

    I work on the premise of 20 degrees maximum rather than perpendicular.

    Shock absorber efficiency is directly related to shock angle, the further out they mount and closer to the wheel, the more effective they are. Canted shocks provide lateral stability. IT's all a bit of a compromise.

    Ideally a shock will be at 1/3 downwards travel at rest. Perpendicular is 100% efficient (Stiff), mount them at 45 degrees and they are only 50% efficient (Soft).

    Staggering shocks, fore and aft controls differential wrap and axle hop under acceleration and braking, one shock is compressing whilst the other is extending. 30 degrees is the practical maximum (Canted) angle.
    Shocks.jpg
     
  4. Devin
    Joined: Dec 28, 2004
    Posts: 2,352

    Devin
    Member
    from Napa, CA

    Thank you gents. Which in your opinion represents the least amount of compromise?
    1. Shocks mounted well outboard but at a 30* angle inclined towards the center.
    2. Mounting the shocks much more vertically with the mounting points about 7" more inboard than scenario 1.

    My suspension is based upon truck arms and a pan hard bar so I am not so much concerned with controlling wheel hop. I am looking for a supple, well controlled ride as opposed to outright performance as this car is a kustom.
     

  5. squirrel
    Joined: Sep 23, 2004
    Posts: 47,071

    squirrel
    Member

    you want a factory car ride, eh? How about mounting them like the factory did on cars in the 50s-60s, they were often canted in at the top around 20 to 30 degrees.
     
  6. Devin
    Joined: Dec 28, 2004
    Posts: 2,352

    Devin
    Member
    from Napa, CA

    Correct. I guess my concern is encountering bind as this is an adjustable suspension and will have a greater range of travel overall. The picture below is where I am currently at. ImageUploadedByH.A.M.B.1467035105.647306.jpg ImageUploadedByH.A.M.B.1467035120.453312.jpg
     
  7. squirrel
    Joined: Sep 23, 2004
    Posts: 47,071

    squirrel
    Member

    Might consider making a lower bracket that moves the lower mounting point inboard a couple inches, so you can have the shock a little bit more vertical. Lots of work, I know.
     
  8. Devin
    Joined: Dec 28, 2004
    Posts: 2,352

    Devin
    Member
    from Napa, CA

    Yeah, that's what I'm thinking too. I was hoping to capitalize on the serrated shock mounts on the ex-NASCAR trailing arms and keep it cleaner, but I think you are right. Thank you.
     
  9. PackardV8
    Joined: Jun 7, 2007
    Posts: 890

    PackardV8
    Member

    As mentioned as near the wheel and as near vertical as possible.

    FWIW, Studebaker trucks had the shocks going forward at a considerable angle. Not much control there. I added this second pair vertically and a couple of inches out closer to the wheels; it made a night-and-day difference.

    [​IMG]

    jack vines
     
  10. 19Fordy
    Joined: May 17, 2003
    Posts: 6,961

    19Fordy
    Member

    Devin, I'm no expert, but do you think that the cantilvered bracket for the Heim joint
    is strong enough so as not to flex and crack over time?
     
  11. Devin
    Joined: Dec 28, 2004
    Posts: 2,352

    Devin
    Member
    from Napa, CA

    You are correct, I am actually replacing the pan hard set up with a beefier unit . I'm just using this right now to locate the axle during mock up. Thank you for looking out.
     
  12. If it were me I would cant them in and mount them so that they are correct at normal ride height. if all you are doing is lifting to jump a curb or speed bump that should not hurt you unless you are racing across the speed bump which basically is a mid truck move not a custom move.
     
  13. Clik
    Joined: Jul 1, 2009
    Posts: 1,874

    Clik
    Member

    I'm no engineer but I would think many stock configurations canted them to offset side to side movement/sway. You have a panhard bar that has taken over that duty in a more positive manor.
     
  14. tfeverfred
    Joined: Nov 11, 2006
    Posts: 15,793

    tfeverfred
    Member

  15. Devin
    Joined: Dec 28, 2004
    Posts: 2,352

    Devin
    Member
    from Napa, CA

    If I rework the panhard bar and mounting, I think I'm able to get an acceptable angle. It's a tight fit but there's no rubbing, binding or interference. Thanks everyone for the advice. ImageUploadedByH.A.M.B.1467086988.847929.jpg ImageUploadedByH.A.M.B.1467087005.554254.jpg
     
    squirrel likes this.
  16. Happydaze
    Joined: Aug 21, 2009
    Posts: 1,026

    Happydaze
    ALLIANCE MEMBER

    Looks to me that the shocks may be too long - there doesn't appear to be enough travel for the bags to be deflated fully. Watch the scrub line if you lower the bottom mount.
     
  17. Devin
    Joined: Dec 28, 2004
    Posts: 2,352

    Devin
    Member
    from Napa, CA

    Thanks for looking out. These shocks have a 9" stroke, I may go to the 7" version once I have everything mocked up and can cycle the suspension with all parts in place. Scrub line is all good, it's just the camera angle.
     

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