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Help!!! Horrible Death Wobble

Discussion in 'The Hokey Ass Message Board' started by telecaster_6, Apr 21, 2007.

  1. telecaster_6
    Joined: Dec 8, 2001
    Posts: 484

    telecaster_6
    Member
    from Dorr, Mi

    So i take my hot rod out for the first few test drives and it has a horrific death wobble when you let off the gas hard or hit a decent bump. Its the kind that doesnt stop till you have the car ablsolutely stopped. I've reset my kingpin inclination (positive caster) to 6 degrees, and reset my toe in (bias ply front runners) to 1/4". The front end was on the car before i rebuilt this time and didnt have a single hint of a wobble before. The only things i've really changed are the steering box and the tires this time around. One tire has a decent flat spot in it from sitting but i havent even got the tires warm enough to see if that will correct itself. The rims are brand new and i dont see any bend or runout on them. I just had the tires all mounted and balanced and i wouldnt see a balance problem cause this horrific of a shake.
    The steering box, an F1, seems decent with a little amout of play in the steering shaft that the pitman arm attaches to, but again, i wouldnt forsee this little amount of wear causing something this bad. Any ideas?
     

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  2. rattlecanrods
    Joined: Apr 24, 2005
    Posts: 352

    rattlecanrods
    Member

    Is it possible to change the location of your damper linkages?

    In the current setup vertical movement of the axle does not create much rotation of the damper. I think you would get more dampening if the linkage was more vertical.
     
  3. telecaster_6
    Joined: Dec 8, 2001
    Posts: 484

    telecaster_6
    Member
    from Dorr, Mi

    i could change the mounts to the back of the axle and run the links to the lever arms straight up, it might gain a half inch of shock travel. I dont see/understand how shock rate could cause the front end wobble like that? The front tires move side to side through the whole range of the turning radius....almost broke my thumb the first time it did it.
     
  4. Could the reverse Ackerman be adding to the problem ? Perhaps you should try toe-out with that setup.
     
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  5. telecaster_6
    Joined: Dec 8, 2001
    Posts: 484

    telecaster_6
    Member
    from Dorr, Mi

    I'll try adjusting for a little toe-out, but i dont understand how it worked fine before with toe-in on the same set-up before.
     
  6. Model A Vette
    Joined: Mar 8, 2002
    Posts: 1,055

    Model A Vette
    Member

    I vote for the play in the steering box. Re-read your first post: you only changed the tires and box.
     
  7. Is it bouncing each wheel alternately, or grabby and tracking steering?

    If it's bumpsteer, I'd look at your new steering's geometry. There are posts here with diagrams about proper side steer setup with hairpins or split bones.

    I use 1/8" toe in, 6-7 degrees caster.

    correcting the ackerman couldn't hurt, it is a steering issue, and you did say you changed the box and the tires, both are steering components.

    I have a buddy with friction shocks (can't quite tell if that's what yours are) he has to snug them up every time he drives the car, or he gets the death wobble at high speed. He's going to tube shocks soon.

    what air pressure are you running in your front tires? put 2psi in a basketball and try to bounce it, then put 30 psi in it and try again. Same thing for your tires. Max rated tire psi isn't always good for a hot rod.
     
  8. Brad54
    Joined: Apr 15, 2004
    Posts: 6,006

    Brad54
    Member
    from Atl Ga

    Did you take it apart and clean/degrease everything before putting it all back together?
    I once did that with my '54 Buick front end, and forgot to regrease everything. You'd be surprised what a little grease will do...with the king pins and a-arms dry, the car was all over the road. I couldn't go half a mile. Add grease, drove straight as an arrow.
    just a thought...
    -Brad
     
  9. roddinron
    Joined: May 24, 2006
    Posts: 2,677

    roddinron
    Member

    Where's the old tires and rims? If you still have them, bolt them on and see if that fixes it. If you don't have them, try to find some that will fit and try them. That "flat spot" makes me wonder.
     
  10. Rootie Kazoootie
    Joined: Nov 27, 2006
    Posts: 7,735

    Rootie Kazoootie
    Member
    from Colorado

    The first place I would check......
     

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  11. hanginlow58
    Joined: Sep 16, 2003
    Posts: 364

    hanginlow58
    Member

    sounds like the same thing my 34 truck did, mine would do it slowing up for a stop sign and if there was a little bump ,front wheels would violently go back and forth, I bought a $ 35.00 steering dampner from socal speed shop and it never has done it again.
     
  12. F&J
    Joined: Apr 5, 2007
    Posts: 13,213

    F&J
    ALLIANCE MEMBER

    I bought a an old mopar roadster in 1971 that was built in the 50s. It had bias tires & stock steel wheels. It was fine until I put mags on the front that had a deeper dish. If I hit a bump with both front wheels it went nuts. Hit the brakes and got worse. Last time it ripped the hood loose & both doors opened & one hinge broke. Scared to drive it at all. The above post about the steering damper would have cured it, I'll bet.

    I ended up putting that car back to stock restored antique, then built another exact same model rod, but with "cross-steer" and never had the problem. Also, old VWs have a stock damper and when the oil leaks out, they do the exact same shake.
     
  13. If your "death wobble" is that bad, it could be that you need a Panhard rod--It sounds like you may be suffering from the dreaded "shackle rock", whereby the natural resonance of your front end is causing the body to sway violently back and forth on the spring shackles. I see that your shackles are tilted in slightly at the bottoms, which is correct, although for comparison I have included a pic of the front end under my roadster pickup which rides perfectly.---Notice that the angle of my shackle is closer to a true 45 degrees than yours. I have always fabricated a panhard rod for my cars which is anchored to the frame on the drivers side behind the axle, and to the passenger side batwing. My caster angle is set at 6 degrees (kingpins tilted towards the rear at the top) and 1/8" toe-in.
     

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  14. Did you install larger in diameter tires on the back?
    A big change will pull some caster out of the front end.

    Did you measure the caster against the frame or against the ground?
    On a level floor is how it's supposed to be done.

    Looking from here it looks like a combination of things are going on.
    Too much tire pressure.
    Not enough caster.
    A loose steering component.
    Lack of adequate damping capability.

    I know the panhards are not usually installed on side steer cars, but it looks like it would help here.

    A steering damper could help, but that's just masking the true problem.

    If the car is coming up in back when braking or simply decelerating that would affect the caster as well.

    What's the backspacing on your new wheels?
    And on the old ones?
    A shallow backspace wheel will have a bit more leverage on the steering system - the steering wheel will be harder to turn.
    The opposite is true, but your wheels look about right backspace-wise.

    This first pic is my 32 with 5 1/2" x 14" wheel.
    Backspacing on it is 2 7/8".
    Granted,a fat radial, but it steers and handles well.

    The other two pics, my 31 on 32 rail project with 5" x 15" wheel and skinnier radial tire.
    Wheel backspace is 3".
    Your wheels look to have similar backspace.
    The rotor on the 32 sticks out further, but that's a function of the Mustang caliper & rotor.
    The 31 has Camaro calipers and rotors.

    First thing I'd try would be to get the play out of the pitman arm area.
    There shouldn't be any play in any steering component, period.

    Next would be an increase in caster, 6 degrees although some guys go as high as 8 and do ok.
    In some cars excessive caster makes for additional effort at the steereing wheel, but yours is light enough that it probably won't affect it too much.

    If caster doesn't do it, install tube shocks.

    I think it was the HAMB a few months back where a guy had similar problems.
    After a lot of posts we find he has no front shocks.
    Adding shocks cured the problem.

    Front end components are heavy and need good control in the damping area.
    I don't think the small friction shocks I see are doing the job.
     

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  15. telecaster_6
    Joined: Dec 8, 2001
    Posts: 484

    telecaster_6
    Member
    from Dorr, Mi

    The wheels are the same as were on the car before, i just changed the actuall tires. There considerably larger diameter, 27" vs. 24" and wider so my track width has changed. I'm gonna yank out the steering box today and try to tighten everything up inside that and try it again with less tire pressure.

    Wish me luck
     
  16. Hackerbilt
    Joined: Aug 13, 2001
    Posts: 6,231

    Hackerbilt
    Member

    When you installed the box did you set it up to be centered?
    Boxes are designed to have a tight spot right on center and thats where it should be when the wheels are straight ahead.
    This is done so any normal wear will be on the tight spot...thus adjustable.
    If there was no tight spot to adjust on, then the worn part would be "below" the surrounding teeth and tightening the box clearances would result in the box being too tight anywhere "off center", resulting in binding and possible breakage.
    Hope thats understandable...

    Anyway...set it up on center and adjust the box correctly when you do your recheck.
    The only time I ever experienced "death wobble" was in a stock van and it was because of a worn part. Replaced the part and all was well.

    Don't like those shocks either though...LoL ;)
     
  17. fab32
    Joined: May 14, 2002
    Posts: 13,988

    fab32
    Member Emeritus

    I posted right after this thread was started and deleted it. Since my solution has already been posted I'll try again. put a So-Cal steering dampner on it and watch some true magic. It's been said that it just masks the REAL problem. What kind of REAL problem do you suppose VW was trying to mask when they put them on EVERY VW that left the factory? Ever try driving one of those little jewels WO the dampner? Hang on.
    Now, I suggest you don't put one on for at least a month. that will give you a chance to chase your tail with every POSSIBLE cause and will make driving just that much more enjoyable when you do try one. BTW, So-Cal doesn't let a car go out of their shop with out one. Probably just a marketing ploy.:rolleyes: Carry on men.

    Frank
     
  18. pasadenahotrod
    Joined: Feb 13, 2007
    Posts: 11,776

    pasadenahotrod
    Member
    from Texas

    Every car I have experienced the "death wobble" in was cured by a new set of kingpins with bushings properly installed and fitted and/or a correct factory adjustment of the steering box done as all correct adjustemnts are done, with the steering linkage disconnected.

    I note,as another did, that your shackles are slightly more angled than 45 as is ideal, but since you had no other problems before I wouldn't worry about that too much.

    Did you install NEW kingpins or at least NEW bushings and have them pin-fitted to a thumb press fit when you built the front end originally?
     
  19. FORD FAN
    Joined: Feb 17, 2003
    Posts: 183

    FORD FAN
    Member

    I run an F1 box on my 30 on 32 rails and had the death shake the very first time I had it on the road. That time it was caused by not having the backing plates tightened very well. Some time later I disassembled the car to do some frame work and a minor death shake reappeared but only at around 50 mph.??? This time it was solved by rebalancing the tires and adding a So Cal steering damper. One thing I would check is to make sure your king pins have no play in them. One time I decided to delete the front shocks becaue they kept ripping loose from the frame. This caused a shake also. It turned out the used shocks from a buddy were the culpret. I got a set of Pete and Jakes chrome shocks and mounts. problem solved.

    Right now my car rolls straight as an arrow( 10 degrees caster) at any speed. Even hitting bumps causes no problems.
     
  20. telecaster_6
    Joined: Dec 8, 2001
    Posts: 484

    telecaster_6
    Member
    from Dorr, Mi

    kingpins were properly installed and have a total of maybe 200 miles on them at this point. I've gone through everything in the front end and everything checks out fine except the gearbox. The shaft bushing is wore pretty bad so i have a new one and a few bearings for the box on the way from macs. i also went ahead and ordered a so-cal damper (only 35 bucks plus shipping) just to be sure. Hopefully i'll have it put back together by next weekend and try to drive it again.
     
  21. FoMoCo_MoFo
    Joined: Mar 30, 2001
    Posts: 1,667

    FoMoCo_MoFo
    Member

    try putting on different tires and see if it's that.

    on my t-roadster I had Radials on it and never had a problem, but then I went with a set of 35 ford wires & the firstone groved "dirt track" implement rag tires and had the death wobble every few times I drove it.

    the first time it happend I went back to the tire shop where I got them installed for a rebalance. when I was there an older gent told me to go see an old timer he knew who did wonders with bias ply tires

    I went and had the tires trued (or shaved as some call it) and never had the problem again. while I was there the old guy who was doing it told me a few pointers:

    keep all the front end components greased & tightend
    & recheck check these things more often than not

    run 5-8 less PSI than max tire pressure

    take off those wire wheels or get them straightened

    Never trust what the "new" tire guys say about Bias Ply tires, since every thing with a tire on it has gone to radial long before most of them have been alive
     
  22. DICK SPADARO
    Joined: Jun 6, 2005
    Posts: 1,887

    DICK SPADARO
    Member Emeritus

    Hi, caught this post late so you already have had some good suggestions for tracing the problem. Although some posts suggested purchasing a shock damper , this is a band-aid for a more serious problem. While use of the dampener might alleviate some of the problem it is still there and use of this part should be avoided.

    In a review of your post pictures the most glaring construction error is the linkage of the shock absorbers. This hookup doesn't do the job correctly. Change the link location so that it moves with the axle as it goes up and down, more of a perpendicular linkage.

    One of the most ignored problems with a high speed wheel tramp is due to inadequate shocks or lack of shocks. In your case the link position does not function with the axle travel and combined with the out of round bias ply tire you can have somewhat of am ill handling unit.

    In short you have no dampening on the front end and between the rebound of the spring and side wall flex of the tire you have no way to control the movements unit they loose their own energy or you stop and start again.

    The second point of attention has already been addressed by other posters and that centers around the play in the steering box. It is important not to have excessive play in the steering box as this will create a position where the slack in the steering will seek a neutral spot and result in the car tracking where it wants and when it wants. This might seem like a small movement but excessive play transitions to bigger movements at the tire patch.

    Remember the initial settings you placed in the suspension geometry are designed to have the wheels seek a straight line track and the wooble indicated that it is trying to but cant. With addition of bounce from poor shocks, an excessive play in the steering creates a fun time driving. Keep us posted on your progress.
     
  23. bobw
    Joined: Mar 24, 2006
    Posts: 2,363

    bobw
    Member

    In agreement with Dick, my son's '27 roadster with quarter elliptic front springs did the same thing. The (tube) shocks were tilted back at about 35 degrees when looking from the side. After moving them to close to vertical the problem ceased.
     
  24. Terry D
    Joined: Apr 2, 2006
    Posts: 124

    Terry D
    Member
    from NY

    I have to say a steering dampner on my 33 Ford solved this exact problem years ago and solved it permanently.Sorry to the anti dampner crowd.
     
  25. Hackerbilt
    Joined: Aug 13, 2001
    Posts: 6,231

    Hackerbilt
    Member

    Why is it nobody gets the point?
    NOBODY is saying that dampners don't work to stop certain types of the wobbles...just that close inspection of the mechanical aspects of the steering/suspension is required to insure that the dampner won't be MASKING a potentially dangerous problem.
    Oddly enough, such an inspection WILL often uncover the cause and allow it to be repaired.

    Dampners DO work and have their place...ABSOLUTELY...but you can't just ignore the potential of serious mechanical problems and stick one on just because they do!

    THIS car was fine until he changed some stuff. Don't you think it important to check that the changes were correctly done with parts in good condition???

    Damn...the silly stuff we argue about sometimes...:(
     
  26. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 4,745

    Ebbsspeed
    ALLIANCE MEMBER

    Please don't put 30 psi in a basketball. It's gonna be very loud AND could take out an eye.......
     
  27. Aman
    Joined: Dec 28, 2005
    Posts: 2,522

    Aman
    Member
    from Texas

    Is the box new and/or did you check it out before you put it on and by the way, why did you replace the box? With the open steering on the car can't you observe it while you go around a corner. Be careful and have someone help you in a large parking lot or something. See if you can see what is shaking. Is the tie rod end on the steering shaft loose? Can you lift it up and check everything, maybe there's a dead cat caught up in it. Just checking to see if you're paying attention. Good luck!
     
  28. alchemy
    Joined: Sep 27, 2002
    Posts: 14,387

    alchemy
    ALLIANCE MEMBER

    Lots of good suggestions.....

    But you steering arms are STILL BACKWARDS. If you are gonna run them to the front you need to make sure you have the correct Ackerman angles. I don't want to be standing on the corner when you try to come around a bit too fast. Your tires will scrub and not track correctly, breaking loose at the wrong moment.

    There have been many posts on Ackerman here, please find one and correct your problem. If not for yourself, do it for the little kid on the sidewalk you'll run over.
     
  29. rixrex
    Joined: Jun 25, 2006
    Posts: 1,433

    rixrex
    Member

    Yeah..I had the same thing going and opened up the steering box and the worm gears inside were thin and sharp from wear, too much play
     

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