Register now to get rid of these ads!

Hot Rods Model A front end steering issues

Discussion in 'The Hokey Ass Message Board' started by bdave_mcc, Jul 28, 2014.

  1. bdave_mcc
    Joined: Feb 6, 2013
    Posts: 50

    bdave_mcc
    Member

    Ok, so i started doing some modifications on my A roadster on the way to a traditional Hot rod build. I have an F1 steering box, used a drop stretched axle to keep mechanical brakes, reverse eye main leaf, and split wishbones. I pie cut the bones to achieve 7 degrees caster and set the front toe in at 1/19-1/8 as recommended my Joe from joes hot rod shop. Over 40 mph the car is all over the road and has serious bump steer issues. I know my drag link is probably at too steep of an angle causing some bump steer, but on smooth straight roads it still wanders all over the place. I know there are probably some other mods i will have to do, but im not sure what is causing the majority of my issue. Wishbone angle to frame? Drag link? or something else. My first go at this, any help appreciated.
     
  2. spinout
    Joined: Jan 15, 2008
    Posts: 333

    spinout
    Member
    from Dallas, TX

    Ackerman angle?
     
  3. Pictures of your set-up?
     
  4. R Pope
    Joined: Jan 23, 2006
    Posts: 3,309

    R Pope
    Member

    Yep, pics would help. Lots of pics!
     

  5. bdave_mcc
    Joined: Feb 6, 2013
    Posts: 50

    bdave_mcc
    Member

    I'll get pics tonight. Stay posted please

    Posted using the Full Custom H.A.M.B. App!
     
  6. A
    Ackerman angle is important at maximum turning radius. the further from max turning the less , less and less important it becomes.
     
  7. You'll basically need to suspect and test/inspect/eliminate every part as contributing to the problem. A Little slop here goes a long way towards the problem.
     
  8. flthd31
    Joined: Aug 5, 2007
    Posts: 584

    flthd31
    Member

  9. bdave_mcc
    Joined: Feb 6, 2013
    Posts: 50

    bdave_mcc
    Member

    I am still going to get pictures so we can figure out whats going on, but for now...essentially every wearing part has been replaced to reduce slop.
    The way i measure toe in is this...First i raise one of the wheels off the ground just enough to spin, then take a marker or something that will make a mark on the tire and attach it to something stationary and slide it up to the wheel. Then spin the wheel making a mark around the circumference of the tire. Do this on both front tires. This way you know you have a true point to measure from reguardless of any out of roundness or wobble in the tire or wheel. Use these lines to take your toe in measurements from. This is probably one of the most acurate ways to measure toe in without an actual alignment machine. It basically works the same as when hooking up an alignment machine, the wheels have to be raised up and spun so the machine can compensate for runout in the tire or rim.
     
  10. SASROD
    Joined: Feb 7, 2007
    Posts: 149

    SASROD
    Member


    Shouldn't you raise both tire equally at the same time to mark the circumference on the tires? If you just raise one at a time it seems that the tire would angle in at the top and the centerline mark you made would not give you the a true vertical line as when the tire was on the ground.
     
  11. I hear what you are saying, I do.
    But if all wearing or moving parts are assumed good, and there is no slop, and the tires are marked and toe measured correctly then your car really is driving fine. Here lies the problem - its not driving fine so ,,,,,,,,,
    That means something stated above is not true & Something is wrong.
     
  12. TANNERGANG
    Joined: Jan 18, 2011
    Posts: 1,277

    TANNERGANG
    BANNED
    from alabama

    Check Caster..........I had a friend that had this problem in his race car...if you hit a bump or when you let off the gas it would dart all over the track....I drove it one lap and came in...put the Caster/Camber gauge on it and he had the Caster set just the opposite way it was supposed to be.....and he is one of those guys that had raced for years .......we all make mistakes.......If I have a steering problem...first check toe, cause it is the easiest.....then check Caster...........usually one or the other are the Culprit..........Sometimes we get in a hurry and think ourselves into a lot of misery.....................
     
  13. bdave_mcc
    Joined: Feb 6, 2013
    Posts: 50

    bdave_mcc
    Member

    As long as the point that is doing the marking is stationary, the angle of the wheel doesn't matter. Here's a mockup pic of the method an old fellow showed me years ago when learning to set up a drag car. Here this is just an old hacksaw blade with a sharpened end to make a mark. I'm not saying that my setup is perfect because I use this method. I just added this in case people were interested image.jpg
     
  14. bdave_mcc
    Joined: Feb 6, 2013
    Posts: 50

    bdave_mcc
    Member

    Front end pics as promised image.jpg image.jpg image.jpg
     
  15. bdave_mcc
    Joined: Feb 6, 2013
    Posts: 50

    bdave_mcc
    Member

  16. One of the first things I see here is the shackles are at the wrong angle and appear too long or the spring is just a tad too long. Also that the spring is nearly touching the axle being static, I'm sure there is witness marks from the motion.

    The shackles at that angle allow the front axle to wag.
     
  17. Baron
    Joined: Aug 13, 2004
    Posts: 3,636

    Baron
    ALLIANCE MEMBER

    Some front shock absorbers would slow down some of the axle movement, and make the steering feel a bit steadier. And as 31Vicky said, the front spring main leaf looks too long.
     
  18. bdave_mcc
    Joined: Feb 6, 2013
    Posts: 50

    bdave_mcc
    Member

    What can be done about the front spring? They are close to the axle but with new bushings they don't touch...yet. It is a stock A spring rearched. I have seen reverse leaf springs for sale that are 29 inches long, I figured they would be too short but maybe one of those would work.
     
  19. TANNERGANG
    Joined: Jan 18, 2011
    Posts: 1,277

    TANNERGANG
    BANNED
    from alabama

    I noticed how the steering arm is bent around and is facing forward...never seen this done before, but I think this could cause the steering to be twitchy....I'd also think the angle of the drag link magnifies the problem ...also you will eventually need a shorter spring....just looking at the pictures, I'd still check the caster with a good gauge...also the drag link looks real close to the frame...it wouldn't take much of a bump to make it bottom out....bottoming out while going around a curve could have REAL NASTY results..........The 7 degrees made into the wishbones is fine as long as it fits the rake of the car.....the higher the rear is, the more caster you will need........

    [​IMG]
     
    Luke stone likes this.
  20. bdave_mcc
    Joined: Feb 6, 2013
    Posts: 50

    bdave_mcc
    Member

     
  21. Rex_A_Lott
    Joined: Feb 5, 2007
    Posts: 1,148

    Rex_A_Lott
    Member

    Wandering on a smooth straight road says slop to me. Kingpin bushings, tie rods, especially. Try tightening up the preload on all the joints where there is a spring. Tie rods, drag link etc.
    I know everybody in the world says " toe in", but we used to set our dirt cars with a little "toe out" to keep them from darting down the straightaway. Try it to see if it makes a difference. If its worse , go the other way. In my experience, you just want a little tension, one way or another, to keep that slop out of the middle.
    Good luck to you!
     
  22. bdave_mcc
    Joined: Feb 6, 2013
    Posts: 50

    bdave_mcc
    Member

    Yeah I have wondered about that as well. I always heard about setting up dirt cars with toe out, a good amount of it actually. Okie joe, who I got my axle from explained to me the reason for toe in is so when the car is traveling down the road any play in the tie rods will basically be pulled rearward and should end up with zero toe when driving. Or something to that effect. Thanks! It's worth a try
     
  23. 53 ford
    Joined: Apr 8, 2012
    Posts: 144

    53 ford
    Member

    The radius rod is too long for that set up. The pitman arm needs to be closer to the end of the radius rod. The farther the pitman arm is from the end of the radius rod the worst the bump steer will be. A good cross steer, a pan hard bar, shocks will cure your ills. Harley
     
  24. Bumpsteer? that Drag Link angle looks pretty severe...

    Posted using the Full Custom H.A.M.B. App!
     
  25. Reversing the stock main leaf can make it grow a tad. Counter intuitive but it does happen. There was a Rod & Custom article on this a couple of years ago. No one really understood it (the article) but it sure had some convincing drawings.

    I think Pete & Jake's offers a reversed eye main leaf for about $40.

    Is your F1 box tight.
     
  26. Hot Rod Rodney
    Joined: Jun 20, 2014
    Posts: 159

    Hot Rod Rodney
    Member
    from USA

    Every time I've thought I had steering geometry issues, it turned out to be just bad tires (even new ones). Try mounting another set of tires and see if things change.

    And yeah, the bump steer is being caused by the difference in angle between the drag link and wishbone. They pivot on different arcs, meaning your wheel has to move to compensate. You can just learn to live with it as part of the "charm" of driving an old car.
     
  27. As you see everyone will notice something first, not always the same thing.

    The spring being re arched is too flat now. That does a bunch of things against you. Makes it too long, changes the rate, decreased clearance at the frame, and the tension in the shackles is off.

    These springs work because they are mounted in tension. The shackles tell the story of the tension being in balance with the weight. 45* is balanced, 0* is too much tension and 90* as your pictures show is not enough tension (or too much weight) It looks like the spring is way to tight on the frame too.
    The tension keeps everything where its supposed to be, and you are way short in the tension.

    Manipulating the ride height by changing/flattening the arch in the spring also changes eye to eye measurements. Flatter equals longer and taller arch makes it shorter.
    Putting some arch back into the spring will do a bunch of things for you, some you will like and some you won't. It will tighten up the front wag, balance the weight/ rate, correct tge shackles, increase the clearance at the spring/frame, correct the clearance at the spring/perch and axle, increas the clearance at the frame/tierod and of course raise the ride height.

    Looks like that drag link violates the scrub line too.
     
    Last edited: Jul 29, 2014
  28. bdave_mcc
    Joined: Feb 6, 2013
    Posts: 50

    bdave_mcc
    Member

    All that sounds great except for the ride height part, ha!
    I was wanting to get this thing low without cutting up the frame...guess that's just not gonna be that easy.

    Posted using the Full Custom H.A.M.B. App!
     
    31Vicky with a hemi likes this.
  29. Not easy without cutting.
    Put a flat crossmember and spring notches with a correct arch and you should be real close in ride height.
    That will fix everything but the tierod to frame issue. For that one the frame needs to come up (aka ride height) , or get cut and boxed so the tierod can be in that space , or the steering arms or tierods need bent down away from frame.
     
  30. verde742
    Joined: Aug 11, 2010
    Posts: 6,267

    verde742
    Member

    Have u cut the ends off of the second leaf, also, did you re-arc the second leaf? seems to me the second leaf is pushing the arc out of the main leaf, making it longer. Also listen to the guys telling you about that drag link angle, its just horrible. Tape a piece of string to outside middle the length of radius rod, leave plenty of extra string, NOW, tie other string end to where front of the drag link connects to steering arm, pull "V" part of string so there is a straight line on radius rod, and a straight line from steering arm to where the "V" meets, That is the angle you want for the drag link.. that will be the pivot of the radius rod and the drag link. No more bump steer..
    HOPE I told this correctly, I know what I mean, hope you get it..

    just another thought the circle racer Always had a huge tire on the right side front where we lived. Go with 1/8th toe in on the street.
     
    Last edited: Jul 29, 2014

Share This Page

Register now to get rid of these ads!

Archive

Copyright © 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.