first time forum user and want to thank everyone for all the great info. I took my 27 dodge roadster for it's first ride the other day and noticed some wobble when I hit large bumps at a slow rate of speed. I think I need a sway bar for the front. any ideas or suggestions where I might get something that would fit? or does it sound like I need a sway bar? Here is my ride (work in progress)
There are a number of things than can cause a "death wobble", I don't think that adding a sway bar would fix the problem. I would start with checking your wheel alignment.
Hey harlowj , From the sounds of it you are describing a bump steer condition. This is caused by difference in lengths between the steering linkages and the suspension linkages. long story short the geometry changes during suspension travels of bumps and dips. If you take a look under a well engineered late model car or truck (I know those are fightin' words around here) from a engineering stand point, the control arms and steering linkages pivot and articulate in relatively the same plane. There is "no bump steer" as the suspension goes through its travel. It also looks like your Ackerman angle could be off, it's a little hard determine from the pic. Here is a great page that explains this angle and caused results clearly. http://www.nationaltbucketalliance.com/tech_info/chassis/ackerman/Ackerman.asp The sway bar main function is to limit body roll when going around a corner or swerving, it doesn't sound like installing one will fix it. I hope this helps!
your Ackerman had got to be way outta whack with that forward steering. I may be blind, but I don't see shocks in the photo ?? You have front shocks right?
Got some shock absorbers hidden on there? Not really a model A front suspension either, but I could be wrong??Just details any how.
Yes as others have said you have reverse ackerman ,not good. Does it go into a violant shake or does it just jerk to one side? If it jerks to a side it is bump steer witch needs front end geometry changes to fix if it is a violant shake it is a death wobble could be a number of things ,ballance ,alignment ,slop in steering box, tie rod ,drag link ,king pins ,or wheel bearings. On my old T bucket it had a very violent shake at about 10-15 MPH I put a VW steering dampner on it and it stoped. I had correct steering ackerman ,shocks ,and all new front suspention parts and it would still shake though, I would fix the steering , put some shock on ,and eleminate all slop you can first then try that as it is just a band aid really but I drove my bucket for anouther 4,000 miles without anouther shake.
I must be blind because I honestly can't tell where the tie rod is located: I think I see the driver side tie rod end? If it is where I think, is the tie rod behind? If that is the joint where I think it is, and if the rod is ahead of the axle, then the ackerman is in the next county. One thing that adds to death wobble is when the king pin centerline does not intersect the ground under the tire. That line gets moved a lot with disc brake conversions as well as incorrect wheel offsets. ...and i don't see shocks either...but I think I see a trailer leaf spring?
Adding more to the puzzle, it looks like you have bias plies on the back and radials on the front. If you have some spares laying around, it might be worth it to switch to all radials or all bias plies. I haven't tried it, so no experience here, but I've heard it's a no-no to mix the two.
wow, you guys rock. I'm going to post more pictures in a couple of minutes. Regards the tires, I actually have a set of coker bias plys that go around it and these were temp tires (yet the ones doing the wobble thing). The car steers great and to get more detailed on the wobble, it happens around 5 - 10 mph and the left front wheel starts going back and forth, however, I apply the brakes and it straightens back out and life is good. None of this happens at higher speeds though. To make it more interesting, this didn't happen (or i hadn't seen it yet) on with the coker bias ply's all around. pictures coming soon. I really need the help as I'm new at this and want to be safe. I'm a "tough guy" but don't want to die. thanks again for all the help.
Lets see a pix from the drivers side of the car. What steering box are you using? Mabe a panard bar is needed.
Here are some more photos: and lastly, a pic with the ugly green rims and cokers (rims are being painted black now.. hence the temp tires).
1. No shocks. You need shocks, all cars do. Anyone who tells you otherwise is trying to kill you with ignorance. 2. Your main leaf in the front spring looks a little too long. Even with a full load on it, there should be a little more tension on the shackles. If there is not, the spring (and chassis) can wiggle between the perches. Try shocks first. I think you might be shocked.
I'm going to ask a stupid question. Based on the comment that it might not be a model A front end (I was under the impression it was), where would I get shocks for such a beast? Anybody got some pictures with shocks utilizing the same type of front end? I actually thought the leaf springs were the shocks! hahaha... man, I'm such a newbie. Maybe I should stick to website design instead of cars.
Which set of wheels were on it during the wobble? I was under the impression that Ford wires won't work with discs. Another hamber PM'ed me to say he just spoke with the owner of ECI about that, just this week. I am wondering if the back side of the wheel flange is supported like a Ford wirewheel drum with the 5 raised bumps. If there is no support, the wheel won't tighten propery. more importantly...if the wires are the ones on the road test with wobble, the offset could be sticking the wheel way out beyond that kingpin centerline situation I wrote about earlier. I am positive that if a wheel/tire is way outside, it "can" or "could" be "a" reason for wobble. True death wobble seems to be a combination of things, not just one item, but is sometimes eliminated by just one fix. IMO
the radials up front was the one doing the wobble. I have not experienced it with the wire rims and the bias plys but then again, I hadn't driven more than about 30 minutes with the wire rims and bias plys. Regards the fits of the wire rims, I've got 4 adapters / spacers for the wire wheels that go from the chevy bolt pattern to the ford bolt pattern. As far as I could tell, seemed to fit just fine. The wire rims will be ready to go tomorrow and I will put them back on and see if I can duplicate the issue. Thanks again for all the help.
It looks a bit like a '32 "heavy" front axle. Pictures are a little grainy, and my eyes are tired. The spit 'bones are NOT Model A. Never mind the glitsy stuff, the shock absorber is the tube with the blue decal in it:
just a question, but is that a friction shock bracket with the holes drilled in it comin from the side of the frame out under the grill?
Very helpful stuff! From a shocks standpoint, do you guys feel I could still ride around town on it in the interim while i order the shocks..etc? I just don't want to make anything worse, if that's possible. thanks again for all the great help. I had no idea about some if this stuff.
NO! Shock absorbers are for dissipating excess kinetic energy in the suspension system and converting it into heat, which is radiated into the atmosphere. Without something in the system to perform this function, you can experience severe, uncontrolled suspension oscillation, which can lead to complete catastrophic loss of control of the vehicle, with little or no warning whatsoever. In short, running without them, even a low-speeds, around town, could get you, or an innocent bystander, killed. Don't do it.
Hey man, That looks like a front axle out of a '35-'40 shoe box ford. That's what a lot of hot rodders used back in the day because they were designed to handle the weight of the flat heads and other heavy V-8's. The shoebox cars were based off of the Model A design with much added beef in the castings to handle said girth. In examining the pics, there appears to be nothing locating the front axle and keep it from moving side to side. This locating is usually done with either a panhard rod or triangulation in the bones. If you were to draw a shape with the spring perches (they look like this http://lbcunited.com/earlyford2/images/Spring Perches .1.jpg ) and the "tie rod ends" that are the rear mounting point for the bones, would the shape be a trapezoid or a square? If it's a trapezoid there is triangulation of the bones and would keep it from moving. If it is a square, the axle has the ability to move back and fourth left to right on the leaf spring perches while the steering linkages stay fixed to the frame through the steering box. The perches are only there to take up the distance change in the leaf spring as it expands during compression of the spring arch. My hypothesis is that the axle is moving side to side rapidly you can check this by pushing perpendicular to the car on the frame while it sits on the floor in your garage and see if the frame moves left to right independently of the front axle. If there is movement, I could totally see one filling his pants while trying to hold on! Have a reputable fabrication shop weld in a front pan hard rod bar. Here's the kit from speedway: http://www.speedwaymotors.com/1935-40-Ford-Front-Panhard-Bar-Kit,3341.html Before it's installed read the instructions. The bar must be mounted to the frame on the drivers side and the axle on the passengers side so that during suspension movement everything compresses as a parallelogram to avoid geometry changing. I hope this is helpful info or the perfect cure for insomnia! Best regards! P.S. your brake lines have too much slack in them and can rub a in the s.s. line from the headlight mount.
Actually, split bones help utilize the axle beam as a sort of sway bar. rocking of the frame trys to twist the beam. Proper triangle-ated bones pivot on the center ball. Shocks are important. don't leave home without them. Low speed wobble can be tough to figure. My problems with it; only could cause it when the left front tire hit a bump and would then start the occilation. I could jump on the brake and stop or speed up and drive thru it. My car doesnot have cross steer like yours tho. I went thru the threads that deal with this and adjusted everything as suggested and don't have the issues any more. Search "Death Wobble" and read what DICK SPADARO has to say. Nice garage floor. More Pictures? If your wires don't give you the problem, You fixed it. And it was a geometry problem. To due with intersecting points and tire contact. Good luck. High speed wobble is the next step when you get up to speed. Tire balance is another issue needed to be adressed with the wire wheels, Todays balancers that locate off the center hole in the wheel can run the wheel in a non-concentric way when balancing. The wire wheels actually locate off the wheel studs and some balancers have an adapter that can be used to mount the wheel to the balancer spindle using the studs and nuts. This trues up the wheel running, makes it the same as when on the car. If you have trouble with wheel balance at 55-65 mph this could be the problem with balancing. Also the bias plys should be balanced warm after driving so the belts are not flat spotted from sitting. Frank
Gas Pumper, You described exactly what was happening to me. I could brake and it would straighten up. The wire wheels and the bias plys did seem to have fixed the issue (or I've not seen it yet again). I'm going to do the shocks as well as the other suggestions just to be safe. Your point about the balance is valuable. I did notice a difference in the ride after putting on the wire rims and bias tires. One of the rims is obviously bent or something. It took 6 ounces of weight to balance and when I was going down the road about 35 - 40mph, I could feel the car sort of going up and down slightly. Do you want pics of my garage floor or pics of my garage? I'll PM you.
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