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Technical Front coilovers with straight axle, caster?

Discussion in 'Traditional Hot Rods' started by Omarsvette, Sep 30, 2020.

  1. Omarsvette
    Joined: Dec 7, 2013
    Posts: 516

    Omarsvette
    Member
    from Arizona

    If caster is set with the front crossmember and no spring is used but instead coilovers, and a panhard bar is used in place of spring to control lateral move. How is caster set?
     
  2. Marty Strode
    Joined: Apr 28, 2011
    Posts: 5,530

    Marty Strode
    Member

    It is set during the build process, with ride angle and height figured in. Minor adjustments can be made when finished.
     
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  3. dana barlow
    Joined: May 30, 2006
    Posts: 4,225

    dana barlow
    Member
    from Miami Fla.
    1. Y-blocks

    No matter what type of springs an shocks,you'll still need 6 to 7* of caster on under 2500lbs,an a little less on car that are more lbs. so 5 to 6*caster.
     
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  4. bchctybob
    Joined: Sep 18, 2011
    Posts: 2,839

    bchctybob
    ALLIANCE MEMBER

    Assuming that you are removing a cross spring and installing coil-overs, there must be some kind of hair pin, four bar or split wishbones locating the axle. With luck you will have enough adjustment to get the correct caster. With split wishbones you will have to raise or lower the wishbone-to-frame mounting point, if it's too low you may have to pie-cut the wishbone near the axle, adjust and reweld it. With hairpins or 4 bar be careful that you have enough thread engagement on the adjusters when you are done. All of this is best done by a competent chassis guy.
     
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  5. lake_harley
    Joined: Jun 4, 2017
    Posts: 1,289

    lake_harley
    Member

    ^^^^ Yes, caster is set by wishbones, 4-bar, or hairpins (tube wishbones). As far as thread engagement on rod ends, I've always gone with a minimum of 1.5 X diameter of the rod end as a good rule of thumb (ie: 3/4" rod end, minimum 1 1/8" threaded in).

    Lynn
     
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  6. Omarsvette
    Joined: Dec 7, 2013
    Posts: 516

    Omarsvette
    Member
    from Arizona

    Gotcha, that’s what I was looking for. I’m using split bones. That’s going to give me the caster.
     
  7. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,903

    gimpyshotrods
    ALLIANCE MEMBER

    It is a common misconception that caster is set by the crossmember. It is not.

    The spring pad on the crossmember needs to be perpendicular to the swing of the arc of suspension movement, not to the caster angle. That angle is required to minimize attempting to flex the leaf spring the "wrong" way, as in bending it fore and aft, rather than up and down. Getting this angle wrong is the reason why so many people think that hot rods are supposed to ride like crap.

    Caster, as others have correctly mentioned, is set by the relationship between the suspension link, or links, and the axle itself.

    If you have links, you set caster by changing the length of the links. If you have wishbones, it's much the same.

    If you have a set of split original, or original style split bones, you set caster by pie-cutting, and welding up the bones, or altering their mounting point on the frame end.
     
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  8. Mr48chev
    Joined: Dec 28, 2007
    Posts: 28,373

    Mr48chev
    ALLIANCE MEMBER

    You only modify a crossmember for increased caster to compensate for the increased caster that we as hot rodders tend to like to help the rods track at speed. The reason is spring bind if you don't. Bchctybob nailed it and Lake-Harley gave great explanations on setting the caster.

    One thing, coil overs usually go hand in hand with a tube axle and split bones don't work the best with tube axles. If you have a tube axle that is.
     
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  9. Omarsvette
    Joined: Dec 7, 2013
    Posts: 516

    Omarsvette
    Member
    from Arizona

    Thanks so much guys, it makes sense. The front crossmember is degrees to match to swing of suspension travel to prevent bind. More sense that caster is set to the bones.
     
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  10. Marty Strode
    Joined: Apr 28, 2011
    Posts: 5,530

    Marty Strode
    Member

    In your original post, you mentioned "no spring is used, instead coil-overs" , the front crossmember doesn't have any relationship to caster. If you are using bones, set the chassis height, check the caster, correct the caster by wedge cutting and welding the bones. Mount coil-overs last.
     
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  11. THE FRENCHTOWN FLYER
    Joined: Jun 6, 2007
    Posts: 3,386

    THE FRENCHTOWN FLYER
    Member
    from FRENCHTOWN

    Re: The amount of caster needed

    When I built my '33 Willys coupe (2350# with me in it) I set it up with 10 degrees of caster. THAT WAS TOO MUCH. It gave me wheel shimmy ("death wobble"). I backed off on the heim ends to end up with 7 degrees - the most adjustment I could do - and added a Fiero steering damper. Now it steers, drives, and tracks great.

    https://www.fierostore.com/Product/Detail.aspx?s=58026&d=324&p=1
     
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  12. Armand J Cote
    Joined: Sep 22, 2020
    Posts: 8

    Armand J Cote
    Member

    I have a 4 springer Nash and just bought 3* shims hope thats enough with tube axle 3800* car
     
  13. Omarsvette
    Joined: Dec 7, 2013
    Posts: 516

    Omarsvette
    Member
    from Arizona

    I’m getting ready soon to weld in my flat crossmember( no spring pad, maybe some tilt to prevent spring bind, but how much). My car is set at ride height. The bones I’m looking to buy have 10* caster built it. To adjust that shorten the hiems? I’m using trans spring, bones, 4” I beam.
     
    Last edited: Feb 1, 2021
    Kevin Ardinger likes this.

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