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308 Castor

Discussion in 'Technical Q&A' started by seschroeder, Jan 15, 2004.

  1. seschroeder

    seschroeder Formula Junior

    Apr 25, 2002
    251
    Alexandria, VA
    Full Name:
    Steve Schroeder
    I am beginning to put the front suspension back togther now. I believe the 308 castor angle is set by "shims" betwee the upper/lower ball joints and the "A" frames. Prior to the front suspension rebuild the vehicle always felt as if once starting to turn it would go "over-center" (to much castor). It goes without saying that when done an alignment is in order. Is it best to start with equal shims on both sides of the ball joints or would it be best to remove some castor now by using two shims on on the (front) and one at the rear on the bottom. Then I assume one is shim is used at the top front and three at the top rear.

    Thanks in advance.

    Steve Schroeder
     
  2. jmillard308

    jmillard308 F1 Veteran
    Silver Subscribed Owner

    May 29, 2003
    5,931
    Perth West Oz
    Full Name:
    John Millard
    Steve
    I run max castor on my 308 - even though the book says it is "not adjustable"
    i.e all the top shims to the front, all the bottom shims to the rear.
    I dont find the steering feel a problem and the advantage is I get a little more camber on turn in.
    John
     
  3. Ferrari_tech

    Ferrari_tech Formula 3

    Jul 28, 2003
    1,527
    UK
    Full Name:
    Malcolm W
    Steve

    You shouldn't set the castor by guesswork, once the suspension is assembled your car should be put on an allignment machine to get accurate geometery figures. From new the shims on the top ball joint were spaced equally each side of the ball joint and the adjustment was done on the lower ball joint - the top shims were only moved if the castor angle could not be achieved by the lower shims.

    The castor angle for your car is 4°


    MW
     
  4. seschroeder

    seschroeder Formula Junior

    Apr 25, 2002
    251
    Alexandria, VA
    Full Name:
    Steve Schroeder
    Thanks for the information. Of course the vehicle will be aligned when the suspension rebuild is complete - have the rear to do yet. Actually I was looking for a starting point and that's the information you gave me. Looking at an alignment sheet of one year ago the castor was 4.9 degrees - too much as I suspected.

    Thanks again.

    Steve Schroeder
     
  5. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
    2,559
    Chicago
    Full Name:
    Philip
    Steve
    Agree with what has been said by Malcolm and others: 4 degrees is what you are looking for. When I had mine apart, I asked Tod (the master tech at Continental) how to put the spacers back in to get it close. His advice mirrored your first post (2 and 2 at the top; 1 and 3 at the bottom).
    Philip
     
  6. ferrarifixer

    ferrarifixer F1 Veteran
    BANNED

    Jul 22, 2003
    8,520
    Melbourne
    Full Name:
    Phil Hughes
    If camber is left at the std minimal levels, then std caster gives the best feel, however, if you want less understeer and better turn in, then you need more camber, this in turn means you can run more castor for greater feel and camber gain on turning.

    Millard is right, set the shims to give max caster, then fine tune it to be both maximum and symmetrical by swinging the camber adjustment.

    You can get up to 6 deg or more on most, but 5 is a good point for general use.
     

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