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Technical Suspension/ caster / radius rods????

Discussion in 'Traditional Hot Rods' started by foxforcefive, Apr 30, 2016.

  1. foxforcefive
    Joined: Apr 26, 2016
    Posts: 24

    foxforcefive

    So the frame I have was put together by someone else and the mounting brackets for the radius rods / wishbones are tacked in place and one broke loose I am going to weld both in fully but I am wondering where should the brackets be welded? Also where do I measure the caster angle? I ask because when I push or pull the loose rod it moves the axle is this enough to mess with the geometry? Here are some pictures thanks for the advice
     
  2. foxforcefive
    Joined: Apr 26, 2016
    Posts: 24

    foxforcefive

  3. F&J
    Joined: Apr 5, 2007
    Posts: 13,223

    F&J
    Member

    If the top of the king pin is perfectly machined flat, use that, not the center of the beam, make sure the angle finder is facing straight ahead, dead nuts.

    The caster needs to be the same as the angle of the spring center mount, so the spring is not in a bind during movement. If there is not enough angle on the mount, to get your caster, then it needs to be changed, by angle shim, or rewelding it back on.

    Before welding rear bone brackets on, check to see if the wheels can steer all the way in both directions to hit the axle stops on each king pin crossbolt nut....without tires hitting the bones. If the tires hit, you need to move the end plates to the inside of frame rails...and if it still hits, swap plates around backwards to have the tie rod end of the bone, coming into the plate from the backside.

    Caster is guesstimated by many things, not the half ass wives tale of 7 for every build. if you have correct scrub radius (offset on wheels) and have a very wide ratio steering box (lots of turns), and smallish tire width up front, then you should do 5 plus. If you had a super fast box, heavy motor and wider tires, you should go with less caster.


    Old repair manual alignment specs in 1940s books, show 4.5 to 9 working range on Ford caster.
     
  4. F&J
    Joined: Apr 5, 2007
    Posts: 13,223

    F&J
    Member

    I see you don't have a tie rod on it. You cannot check the full turn on the wheels correctly without a tie rod, and the toe setting needs to be close to check the axle stops. Toe in at 1/8" or 3/16"
     

  5. badshifter
    Joined: Apr 28, 2006
    Posts: 3,344

    badshifter
    Member

    And the axle caster should be set while frame and axles are at ride height both front and rear. You don't need all the springs in the packs to do that you can remove all but the main spring and use spacers to make up the difference. The radius rod bracket should not be made permanent until that is set. If you weld the radius rod brackets at your current height when there is weight on the car the caster will change. Not to pile on, but you really should mock up spindles, arms and steering box at the very least to make sure there is no interference. Side steer the drag link may interfere with the radius rod.
    But to go back to what F & J said above, the spring mount angle needs to Match the axle caster angle at ride height. You should recheck that angle before you go any further because that is your built-in caster angle
     
    Last edited: May 1, 2016
  6. foxforcefive
    Joined: Apr 26, 2016
    Posts: 24

    foxforcefive

    Thanks f&j I will measure from the king pins but the radius scrub will be off as I am using disc brakes with 35 spoke wheels and have wheel adapters
     
  7. foxforcefive
    Joined: Apr 26, 2016
    Posts: 24

    foxforcefive

    Thanks badshifter I will just tack them for now and will be getting tires tie rod and steering before the full weld
     
  8. F&J
    Joined: Apr 5, 2007
    Posts: 13,223

    F&J
    Member

    I should never post at midnight ... the side steer is what I really was thinking about when I said he needed the tie rod...

    On a side steer only, the drag link actually moves more in one direction full lock, than full lock to the other opposite turn, and that is due to ackerman. It's very confusing until you watch it when assembled. Having the tie rod installed and toe set, lets you test the side steer for full turns both directions, to see if the box can push it that far.

    and a side steer with a straight drag link can also hit the tire, and that is another reason to have all components in place before welding anything. It's a balancing act to get everything to clear, and things need to be tweaked sometimes.
     
  9. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,319

    gimpyshotrods
    ALLIANCE MEMBER

    Is it me, or does the engine setback make it look like you are going to be sitting in the trunk?

    What is the wheelbase on that chassis?
     

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