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Flipped Uprights. Possible Caster Issue..

Discussion in 'The Hokey Ass Message Board' started by redequity, Aug 24, 2013.

  1. redequity
    Joined: Oct 13, 2011
    Posts: 6

    redequity
    Member

    Hello all. I'm new to the Hamb and recently started building up a 1949 Ford Convertible. I'm in the process of flipping my uprights and have a question regarding caster. I've read many discussions regarding this topic and most say to swap the driver and passenger uprights during the flip process. I have a background with building long travel off road cars and somewhat versed with bump steer, etc. that effect ride quality. I see that if the uprights are swapped from side to side, the caster becomes negative, or reversed. This can't be good as the car will not self center and track correctly..

    Question: Why are so many people advising to swap uprights? Why not just flip the upright and keep it on its original side. (Obviously the spindle will not get flipped in this process).

    By not swapping the spindle, the caster remains the exact same as it was originally. The only real change I see it that king pin location simply gets moved back about 3/4 to 7/8 back thereby shorting the cars wheelbase by the same amount.

    Please help give some insight and let my know why I need to swap from side to side.. Thank you in advance!! Danny

    PS I know one can purchase dropped uprights.. and their benefits... I'm hoping this thread stays directly on the topic of distorted/changed geometry caused by flipping spindles. For example, flipping the uprights pushes the spindle out slightly while increasing the scrub radius.
     
    Last edited: Nov 23, 2013
  2. Russco
    Joined: Nov 27, 2005
    Posts: 4,187

    Russco
    Member
    from Central IL

    Doesn't it change the camber a bunch when you flip the uprights? I thought that was the issue when flipping them.
     
  3. CoolHand
    Joined: Aug 31, 2007
    Posts: 1,926

    CoolHand
    Alliance Vendor

    I'd say it would depend almost entirely if the kingpin angle matches the stock camber angle and whether the upper and lower bushings are the same type and size.

    In other words, if at ride height the long axes of your kingpin and your upright are exactly (and I mean exactly) parallel and the upper and lower pivot bushings on the upright are both the exact same type and size, you should be OK to just flip the upright and go.

    The trouble is, I don't think I've ever seen one of these types of front ends that I would swear actually had parallel kingpin/upright axes OR had the same size bushings top and bottom.

    The caster angle should be the same regardless of upright orientation (the diagonally opposite angles in two right triangles connected at the hypotenuse are equal), but the camber/kingpin angle thing might cause trouble.
     
  4. redequity
    Joined: Oct 13, 2011
    Posts: 6

    redequity
    Member

    Yes it does change the camber but that's fixable by heating and bending. The issue I'm perplexed about is caster. Why are so many people stating to swop sides when doing so causes reversed caster, negative rather than positive?? Please see my photos coming ahead.. Thanks for the reply!! Danny
     

  5. redequity
    Joined: Oct 13, 2011
    Posts: 6

    redequity
    Member

    Hi Ryan.. I'm with you all the way and in this case, like you projected, the kingpin caster is not parallel with the A arm pivot points. please check out the photos I'm going to post. The series of photos help clarify the reversed caster when swapping the uprights from driver to passenger and so on.. Thanks for you input!!!!! Danny
     
  6. mikes51
    Joined: Oct 4, 2001
    Posts: 2,195

    mikes51
    Member

    People are erroneously swapping the upright and spindle together. You are correct this is wrong for the caster/kingpin motion. Imagine the axle (spindle) never leaving the wheel, then the upright from the other side is put in place. Then next required is a major heating and bending of the upright to get your kingpin angle right. Just as you suspected.

    On some uprights I believe the caster is in line with the a arm pivot points so no change there.

    Here is an old thread with a picture.
    http://www.jalopyjournal.com/forum/showthread.php?p=950259#post950259

    scroll down to post 7 for my sketch
     
    Last edited: Aug 24, 2013
  7. redequity
    Joined: Oct 13, 2011
    Posts: 6

    redequity
    Member

    The first photo shows the upright simply flipped. Notice line B is not parallel with line A due to built in turning caster. Shoebox fords caster is adjusted the entire upright (line B) by moving the pivot points on the a-arm forward or back.

    Notice how line B is tilted back in relationship to line A. The second photo shows how simply flipping the uprights (NOT SWAPPING FROM SIDE TO SIDE) keeps the correct positive caster. The only thing that does happen is the spindle kingpin (with built in caster) gets shifted from one side of line A to the other side of line A. This shift shortens the cars wheelbase by about 3/4 to 7/8 which might cause or shift rubbing problems.

    The last photo shows how the uprights are FLIPPED AND SWAPPED FROM SIDE TO SIDE (this was done in ms paint so the evidance can be seen in the red letters.. flipped and reversed). This is where sh@#t hits the fan. The caster is now reversed which will keep the car from naturally seeking a streight line while driving. Notice how flipping/swapping keeps line B on the same side of A when comparing the third photo with the first (UNflipped/UNswapped). Only good news I can see in this situation is that the wheel base is not changed..

    I simply can't find the reason why anyone would want to swap. Especially on a Shoebox or Merc...

    Thanks!! Danny
     

    Attached Files:

    Last edited: Aug 25, 2013
  8. redequity
    Joined: Oct 13, 2011
    Posts: 6

    redequity
    Member

    Hmmm. I might have figured out why everyone swaps sides when flipping uprights... Must be because brakes have clearance issues if not swapped side to side. If not swapped, the kingpins new location behind the upright center line (line A in the photos) will cause brakes to hit upper A arm/upright pivot bolt. I'm going to be running disc brakes behind the spindle to cure this issue. I have to modify my disc brake conversion to run caliper behind spindles. This is the only reason I can figure people would make such a huge sacrifice (reversed caster) to make flipping possible???? Danny
     
  9. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,578

    Rusty O'Toole
    Member

    It depends on the car. Some spindle supports have mountings or bolt holes in a certain position, when you flip them over the mountings are on the wrong side. Swapping them from side to side corrects this.
     

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