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Technical Alignment information.

Discussion in 'Traditional Hot Rods' started by hardtimesainit, Nov 30, 2017.

  1. hardtimesainit
    Joined: Jan 24, 2009
    Posts: 158

    hardtimesainit
    Member

    Changed tires to 'big/littles'. To your knowledge, does this change from end geometry and need new alignment ? What are your experiences/thoughts ?
     
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  2. alchemy
    Joined: Sep 27, 2002
    Posts: 11,112

    alchemy
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    It will change caster for sure.
     
  3. DdoubleD
    Joined: Nov 18, 2009
    Posts: 194

    DdoubleD
    Member
    from Michigan

    Pics? Caster, slightly depending on wheelbase. Drive it first before you worry about.
     
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  4. hardtimesainit
    Joined: Jan 24, 2009
    Posts: 158

    hardtimesainit
    Member

    Thanks much. I kind of thought as much, but guess is not good enough. Situation is that I had all four 600x16s and all seemed ok. Then I switched to the B&Ls and I have the front end wondering around the road...with every piss-ant that gets in the way. What's up with that ? Maybe switch back and see if something has changed/worn ?
     
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  5. BJR
    Joined: Mar 11, 2005
    Posts: 3,384

    BJR
    Member
    from Wisconsin

    With the nose down you have less caster then it was when level. It makes it more likely to wander around on the road.
     
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  6. sunbeam
    Joined: Oct 22, 2010
    Posts: 2,939

    sunbeam
    Member

    If you changed the tire 4" it would only move the axle 2" the caster change in degrees would not be much.
     
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  7. dana barlow
    Joined: May 30, 2006
    Posts: 2,767

    dana barlow
    Member
    from Miami Fla.

    Caster,if having any prob. should be checked ,an if it's less then 6* now,it can wonder/ so go up to 6*{ if car is very lite{less then 2200lbs} an short WB,go to 7*.
    ****Now there is one more thing that happens a lot when guys go to Big/little=rims get changed and often have off-sets that are too far out from center of car=on front end with lots of out side offset,the rim/tire now has exter big lever,so every bump feels bigger an steering feels ruffer. That also adds scrub to front end. If you added front rims with wrong off set,you need to replace them. @ 75years old ,I've herd a lot of BS about"I like the look of front wheels sticking out that way and the wide track is cool=Don't be that stupid,it looks like some fool that dosen't know cars or what a good driving car feels like.
     
    Last edited: Nov 30, 2017
  8. squirrel
    Joined: Sep 23, 2004
    Posts: 37,415

    squirrel
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    Did you change the wheels? or only the tires? Different wheels can affect things.

    But also tires are not all made the same

    And tire inflation can make a big difference, make sure the pressure is as low as it ought to be on a light car.
     
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  9. s55mercury66
    Joined: Jul 6, 2009
    Posts: 1,568

    s55mercury66
    Member
    from SW Wyoming

    If the caster was marginal to begin with, yes it can cause this problem.
     
  10. hardtimesainit
    Joined: Jan 24, 2009
    Posts: 158

    hardtimesainit
    Member

    Hey Dana,
    Well, @ nearly same age. Maybe that's why you make good sense to me !
    I took a set of 600-16 Kelsey Hayes rims/tires off. Then put B&Ls , also mounted on 16" Kelsey Hayes rims back on: 550x16 front; 700x16 rear Good tires all and air pressure regularly set to 32lbs.
    The car is a '30 ford roadster, full fendered w/32 banger, in the less than 2200lbs range and short wheel base (stock).
    So, per your input, I will tell the shop to put 7* caster on my 4" dropped front axle...is that correct ?
    I never realized that changing out the front tire size made such caster (change/need) difference. So, if changing front tire size like I did....or any large change (to smaller) to front tires makes it necessary to correct caster ?
    I just put an Okie Joe front 4" dropped model A axle under it. Guess I'll have to have it adjusted/bent for proper caster.
     
    Last edited: Dec 1, 2017
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  11. squirrel
    Joined: Sep 23, 2004
    Posts: 37,415

    squirrel
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    drop the tire pressure first, don't cost nothin to try it....to around 24 psi. Maybe go down to 20 if it seems to be getting better.

    You can do the math to figure out the caster change from the tire swap. The caster will change by the arcsine of the tire radius change, divided by the wheelbase.

    If the tire diameters are 5" different, and you have a 104" wheelbase, then the caster angle changed about 1.37 degrees.
     
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  12. alchemy
    Joined: Sep 27, 2002
    Posts: 11,112

    alchemy
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    Bending an axle to correct the caster is not the preferred method. Old Ford axles are supposed to be flat, not bent. Do you have Ford wishbones holding the axle, or hairpins? Many guys will cut and reweld the wishbones to correct caster problems, but that is probably not something your alignment shop would do. I guess since you have a forged axle it would be doable to bend the axle.....
     
  13. dana barlow
    Joined: May 30, 2006
    Posts: 2,767

    dana barlow
    Member
    from Miami Fla.

    Note if even needed ?
    Do not bend any axle for any prob,if its not been wrecked an bent or even then better to replace it if bent. Dropped axles done by a pro are fine,but there camber is set right by pro an not to be messed with{Camber is not adjustible} but caster is by arms,not part of axle its self. The bone's {arms}is were adjustmints for caster is done. Not axle. The're two ways;The "V" of arm if stock "A" set up, has a ball mount back at center of car,lower spacer mounts are made for adding caster,{some home}. /The others is bending or pie cutting arms to add caster. If arms are split out to each side of frame? Then the mount points on rear of arms can be lowered.
    Always good shocks are needed.
     
  14. Happydaze
    Joined: Aug 21, 2009
    Posts: 408

    Happydaze
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    My very rough calc says that raising the rear tire diameter by 4" (thus raising the rear axle centerline by 2") will decrease caster by a little over 2 degrees. If you originally had a nice 7 you've now got a poor 5-. If you had a marginal 6 you've now got a very poor 4- and so on.

    You appear to have camber adjustment (fixable by axle bending) confused with caster adjustment (not fixable by axle bending (well twisting really) as far as i know, but yes it could be possible!) - caster adjustment has already been explained (dropping the pivot point (ball?), or pie cutting the bone).

    There isn't any caster in the axle as such. The caster is determined by the way the axle is mounted to the frame - and the caster angle is a real measure, not a relative to the frame measure.

    Chris
     
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  15. sunbeam
    Joined: Oct 22, 2010
    Posts: 2,939

    sunbeam
    Member

    As an experiment I took a stick of square tubing and a machinist level and at 100" raised it 2" it changed the reading 1.3 degrees which is more than I expected.
     
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  16. squirrel
    Joined: Sep 23, 2004
    Posts: 37,415

    squirrel
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    Me too, I would have expected it to be 1.14 degrees.

    (the arcsine of 0.020)
     
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  17. hardtimesainit
    Joined: Jan 24, 2009
    Posts: 158

    hardtimesainit
    Member

    Hey Jim,
    Thanks for your input. Pressure change is easy and I'll try that first to see wha
    Thanks much for ALL you guys 002.JPG 003.JPG 004.JPG 006.JPG 008.JPG 009.JPG input, so far , easy to grasp/helpful !
    Here are some pics of car. Hope they are what is needed for your scrutiny. More if needed.
     
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  18. BJR
    Joined: Mar 11, 2005
    Posts: 3,384

    BJR
    Member
    from Wisconsin

    Space the wishbone ball mount down to add caster, way easier then pie cutting the bones. Just don't space it so far as it gets into the scrub line.
     
  19. hardtimesainit
    Joined: Jan 24, 2009
    Posts: 158

    hardtimesainit
    Member

    Hey Chris,
    Caster and king pin inclination...same ?
     
  20. jaw22w
    Joined: Mar 2, 2013
    Posts: 342

    jaw22w
    Member
    from Indiana

    No. Caster is the angle of the king pin as viewed from the side. KPI is the angle of the king pin as viewed from the front.
     
  21. 550-16 = 27.36 diameter - ( published info)
    600-16 = 28.30 diameter
    700-16 = 30.60

    That's 2.3 up in the rear plus the 0.94 down in the front.
     
  22. King pin inclination is fabricated into the spindle.
     
  23. squirrel
    Joined: Sep 23, 2004
    Posts: 37,415

    squirrel
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    that's at the top of the tire, right? the car moves half that far.
     
  24. True dat. More caster is almost always the cure for a wandering car.
     
  25. pitman
    Joined: May 14, 2006
    Posts: 4,093

    pitman
    Member
    from Hampsha

    Seems 'Toe' is a second contributer, when too little may cause wanderin'.
     
  26. hardtimesainit
    Joined: Jan 24, 2009
    Posts: 158

    hardtimesainit
    Member

    Ok, I got the picture, so two different angles involved on one spindle...i.e., caster =front or backward slant (from side view); KPI+in or out slant from front view , eh . Proper caster + good tracking; Proper KPI = good toe ??

    Question : if a guy were to reverse the B&Ls front to back (same tires) what will occur ?
    Back in 50s (?) was called (Spanish ?) rake ? can't remember back that far..lol
     
  27. Fordors
    Joined: Sep 22, 2016
    Posts: 697

    Fordors
    Member

    KPI is used to lessen the amount of camber needed. A line drawn through the center line of the k/p should meet the c/l of the tire at the pavement, and that is called zero scrub. As suspension systems (when k/p’s were vertical) evolved it was realized that proper KPI would aid in the wheels returning to straight ahead coming out if a turn with the added benefit of less tire wear that was common when a lot of camber was used.
    This is what Dana referred to in his post Thursday, when the wrong wheels are used to show off those finned aluminum Buick drums then more tire scrub is the result. The KPI/wheel combo and resulting scrub radius is not a concern on your car, unlike those guys with a lot of positive scrub who either don’t know any better or don’t drive enough to notice anything odd about the way their car handles.
     
  28. Mr48chev
    Joined: Dec 28, 2007
    Posts: 21,595

    Mr48chev
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    I've read through this a couple of times and most of the suggestions are pretty good along with most of the info being right. If you haven't had it on an alignment rack since you changed the front axle I would go have it checked out and see what the caster and toe in are. I'd think the camber would be spot on as that is set when they drop the axle, That is one reason guys send their Ford axles to Okie Joe's to be done.
    I'm wondering about that drag link angle. How much did the angle on that change after you installed the dropped axle? The extreme difference between the angle of the drag link and the bones might be causing bump steer or throwing the steering feel off from where it used to be.
    Looking at the photos again, that is the first Ford with bones outside of a rat rod I saw a while back that I remember having the tie rod above the wishbones. Proper mounting would be on the bottom bolts on the spindle with dropped steering arms. That would let you drop the end of the hairpin down a ways to lessen the drag link angle.
     
    Last edited: Dec 2, 2017
  29. Fordors
    Joined: Sep 22, 2016
    Posts: 697

    Fordors
    Member

    Your concern about the angle is well place, but those look to be original Model A spindles and steering arms.
    I’m not real familiar with that A stuff but I think if an attempt was made to bend the arm for the d/l the axle gets in the way of connecting things.
     
  30. Did you do the drop axle change and the B&L tire change at the same time ?
    Or did you do the axle and it drove fine with four 600-16 tires?
     

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