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Technical Model A Caster

Discussion in 'The Hokey Ass Message Board' started by kevinwalshe, Nov 21, 2017.

  1. kevinwalshe
    Joined: Apr 22, 2010
    Posts: 429

    kevinwalshe
    Member

    Hey guys, tried the search function but no answers just yet. I split the wishbones on my car and it seems the axle is pulled back and under the front a bit too much. I understand that I can probably pie-cut the bones close to the axle, but should I wait to do this for when the motor is in and under its normal weight, or should I let the axle drop and have the spring basically center it in the stock crossmember? Any help getting it all dialed is appreciated. I'm not really sure how to properly measure caster to begin with. It's got a stock crossmember, spring, and a dropped axle. Thanks fellas.
     
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  2. Sheep Dip
    Joined: Dec 29, 2010
    Posts: 1,572

    Sheep Dip
    Member
    from Central Ca

  3. GordonC
    Joined: Mar 6, 2006
    Posts: 1,702

    GordonC
    ALLIANCE MEMBER

    If you can get the car down on the wheels and tires that you are going to run along with the motor in the chassis that would be best as it most resembles your finished ride height and angle. Using an angle finder like the one above you can set it on top of the king pin to get a reading and adjust from there. I believe they do make wedges to adjust the angle the spring sets in the pocket or you can cut and adjust the bones to suit your needs. As I understand it you need between 5 to 7 degrees of caster.
     
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  4. BJR
    Joined: Mar 11, 2005
    Posts: 6,007

    BJR
    Member

    Or drop the back end mounting point of the bones instead of pie cutting them to get the correct caster angle.
     
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  5. kevinwalshe
    Joined: Apr 22, 2010
    Posts: 429

    kevinwalshe
    Member

    Thanks guys, I will order up one of the degree markers and fab up the tool in the above mentioned link. So just to be clear, the axle must be forward 7 degrees, or back and under 7 degrees?
     
  6. PAracer
    Joined: May 21, 2007
    Posts: 91

    PAracer
    Member

    Top of the kingpin should lean back. If using side steer, when deciding pie-cut vs. lowering the rear mounting point of the wishbone consider bump steer. This can be corrected by moving the steering box, shortening the pitman arm, bending steering arm on spindle, or moving the wishbone rear mount. Goal is for the arc of the drag link to be as close to the arc of wishbone through the full suspension travel to reduce bump steer.

    Tex Smith’s book “How to Build Real Hot Rods” has a good section on this.
    Sent from my iPhone using H.A.M.B.
     
    Last edited: Nov 22, 2017
  7. kevinwalshe
    Joined: Apr 22, 2010
    Posts: 429

    kevinwalshe
    Member

  8. Marty Strode
    Joined: Apr 28, 2011
    Posts: 4,291

    Marty Strode
    Member

    I would buy a digital level from Home Depot, more accurate than the needle type. They have a magnet on the base.
     
  9. PAracer
    Joined: May 21, 2007
    Posts: 91

    PAracer
    Member

    Either tool will work. Come to think of it, so will the free level app for your iPhone.

    Just make sure to take into account any slope in the floor. If the floor isn’t level add or subtract floor level from caster measurement to determine actual caster angle.


    Sent from my iPhone using H.A.M.B.
     
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  10. 1946caddy
    Joined: Dec 18, 2013
    Posts: 1,510

    1946caddy
    Member
    from washington

    I don't know the cost of the Home Depot item but I got one from Harbor Freight and it's worked great for me for years. I also use a large socket thats fits over the end of the king pin for a flat base to set it on.
    https://www.harborfreight.com/digital-angle-gauge-95998.html
     
  11. If you end up with spring bind get some adjustable spring perch's
    .
     

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