Ok, lets start here, that piss *** shock absorber mounted sideways on the tie rod is a bandaid for another problem. The situations regarding death wobble terminology on an I beam relates to a bunch of different problems either with dynamic tire balance or just basic errors in engineering that all have to be addressed. Here is a short version. First is to determine if this is an out of balance problem, engineering problem or just some worn out parts. Before attempting to totally trouble shoot this it is important to recheck your car. Start by checking all movable connections. There should be no play in any bearing or joint. This also means no excessive free play in the steering box. There should be no brackets that flex and all mounting bolts are secure. Start by determining if it is a balance problem. Place the vehicle on jack stands front and rear. Allow the tires to normalize with no load and then air up all tires to an equal pressure. Remember due to construction Bias ply tires have a tendency to follow the road imperfections more than radial tires so this gives you a false sense of road feel. Don't get this misinterpreted as bump steer, thats a tracking issue. Make sure the brakes are not dragging. Now even if you have had the tires spun balanced, spin the tires by hand and reference the tread and the the side wall to a fixed point to determine if the tread or sidewall surface is irregular, This will show out of round tires due to poor construction or damaged cords. Next spin the tire and note where the valve stem stops, respin the tire and note where the valve stem stops, repeat one more time. Each time the tire should stop in a different spot. If the tire stops in the same area all the time there is a tire balance issue that should be checked. If the tires checked out ok then remove the tire and wheel and repeat this process with the brake drums. Worn brake drums,redrilled brake drums and Buicks to early Ford hubs are easily registered off center and create a balance problem that show up at moderate to higher speed. Buick conversions are know to have large weights bolted to the drums and may people remove them as the look ugly. They are there for a reason. The heavy spot will always register to the low side. While the wheels are up in the air make sure that you have no excessive play in the wheel bearings side to side or up and down. With the vehicle still off the ground remove the lower shock bolt and check the shock absorber condition, it should be stiff to compress and stiffer to extend when exerting pressure with one hand. If you can woosie the shock in and out its not a very functional shock. Bad shocks or no shocks are potentially a source of a problem. Re mount the shocks. This operation does two things it insures that you have adequate control of the spring as it cycles and as adequate control of the tire as it rolls over the imperfections of the road and distorts and returns to round. Poor shocks or no shocks allow a spring to oscillate until it runs out of energy after hitting a bump which is sometime interpreted as a wobble. The next step is to begin checking the engineering of the car. If you have bought a car or had one built it is important to know which way the wheels are pointed. To do this you may have heard the NASCAR guys talk about stringing , well that is just what you do. This determines the ch***is center line and the relationship of the front and rear axle to being square to the centerline of the car and being square to each other. You take a plumb bob and using reference points from the ch***is and from the axles you can determine the center line of your vehicle and from this point you can determine if the axles are in the vehicle square, offset to the left or right or front to back. For the sake of time this procedure was posted on JJ tech and you can search it. It is important to have both the front axle and rear axle track correctly, and just because you counted even threads on the adjusters doesn't mean that the axle is positioned square. If the front axle hub to hub center line is not square to the center line of the car or the rear axle a tracking effect is created which draws the leading tire to an imaginary center line as the tire spins. If this center line is not the axle center line then there are issues. The next step is to now check the dynamics of your ch***is. If you have throughly checked the balance on the tires and they are ok the next step is how your ch***is reacts in operation. Remove the drag link and set the front wheels with a carpenter square, square to the front axle at 0 toe This may require you to loosen or remove a tie rod end and insure both wheels are square 0*. Now check to see that the steering box is registered with the steering sector at center. Not just that the pitman arm is pointing what you think is correct. This insures that the adjustment of the box is correct. Now re index the pitman arm so that the drag link is as parallel to operation as possible. If you have a side steer box you want the longest drag link you can get to cut down the angular motion gain during body roll or suspension compression. Do not re hook the drag link. Move on to the caster setting can be done with a simple bubble protractor scale from Sears, use the top of the king pin or the spindle boss and measure the inclination rearward. The setting should be from 4-7* tipped rearward and equal on both sides. Move on to set the toe setting. You can simply take a tape measure at the hub height of the tire and measure the difference between the front sidewall of the tire and the rear sidewall of the tire or if you want to be more technical you can make some toe fixtures from masonite or plywood that mount against the outside sidewall of the tires and use the outer edge for a measurement point. The adjustment that you should be looking for is 1/16" to 1/8 " toward the center of the car. Adjust from the previous 0* toe square setting by opening up the tie rod ends or closing them inward and reinstall if you removed it in a past operation . Without moving the corrected toe setting reinstall the drag link, it may be necessary for you to readjust the length also. This now gets more complicated if you have flipped or bent the steering arms, the ackerman principle is not cut and dry. It basically refers to the axial rotation of the spindles generating a steering arc gain on the inner wheels. What happens when steering arms are randomly bent or fore shortened, creates a series of dynamics where the inward tire and the out ward tire try to work against each other. If they do not turn in close conjunction with the radius of the turn they begin to seek a self center position and they can do this even as the return to center as the spinning dynamic of the tire tries to find a center of operation. This become a giant math problem and one of the reason that you should not be bending, dropping or cutting steering arms. I don't care what you saw in a 1950 Hot Rod book it was probably a trailer queen then too. This can keep going on, this is my approach to help you trouble shoot your issue. Tighten everything up and drop you car off the jack stands and take it for a spin. If you still have this problem then there is some issue that is an engineering issue and a picture will be necessary
I got a question to highjack this thread Has anyone had wobble with radials? Are we all running bias tires and having problems? I worked on trucks and buses for years, parallel leafs and beam axles. We had wobble years ago with bias plys, but I can't ever remember having issues like that with radials. I though we got good and fixed the problems but maybe it was the tire style that contributed to the problem? But then, I was at a cruise tonight and at least two of the billet/street rod things with straight axles had dampers and radials. It just don't look right, having that damper clamped on the axle. frank
Tire balance is not the issue on the 2 cars I have been in, because the speed was SO slow, that the tire would have to be off by half a pound! Drive out of it? that's more acceptable? The 2 cars I'm talking about were so violent that parts were coming loose. The rad is leaking now. And the 34 has 4 radials...to answer a question. Yes a damper is Non-trad, but I won't ride in a car that wobbles. just asking for trouble. That long thread pretty much said there was no know single cause. All this armchair fixes mean nothing on the problem cars. I want to hear from someone who fixed one, that no-one else could...and without a dampner or panhard bar. Talk is cheap.
Ok while I was typing you were posting more info. You have two issues that are easily viewed in the pictures , you have too much angle in your drag link and it appears to me that you have screwed with the lower steering arms to clear the wishbones. Two wrongs don't make it drive better. You are initiating a serious bump steer under axle compression. If you just plot a small picture of the relationship between the centers of arc travel on the radius rod using the rear mount as a center point this will show you the arc travel of the axle. You then can create a secondary arc travel of the steering arm center using the rear position of the radius rod also. You can see that as the axle swings in a circle these points stay in the same relationship with each other. Now draw another arc travel out to mimic your drag link. You will see that the new arc creates a conflict between the position of the radius rod arc. The swing of the drag link arc only intersects the swing of the steering arc in one spot. This means the steering is only steady in one instance of travel. As the axle rises or lowers the axle arc draws away from the drag link arc and initiates a steering function as you deviate from stationary ride height. This action induces a steering direction of turning to the left on compression and right on extension. You must have to hold on that wheel pretty tight.
If it's that bad that it's shaking the car apart, you need to do more of the basic checks to get it as good as possible before the damper goes on. Tire pressure is a factor,too. you need to play, 2 lbs at a time till you get that the best you can. Start at 30 and go over the same road, each time reducing 2 lbs in the fronts til it gets better and than worse again, than you know where air pressure should be. Mine now only shakes occ***ionally, and I can drive thru it. Tonight I went about 30 miles, hit some good one wheel holes and bumps and had no shake. Some times it's the creep speed, and by 15-20 its gone. some times it's the 30-40 and by 50 it's gone. Holding a steady speed makes the wobble amplify. Nailing the brakes takes a complete stop to calm it down. quickly accelerating stops it in a second. Dirt modifieds and sprint cars live with this, too. They drive thru it.
Yep **** has it on the drag link angle. As soon as I looked at your pictures and saw that draglink angle I though BUMP STEER ! And being you said the problem was with a bump at low speed that looks like one of the causes for sure. The drag link needs to be a parallel tothe ground as posiable. My .02 once you get everything mentioned checked out a damper is going to be needed.
i have never had the car out on the open road to see...just through the neiborhood it does it at 0-5 when hitting a small bump...on a smooth surface it seems ok...i need it safer before i venture out .
A (semi) OT question. Do you have a Panhard bar for the front (or a 'dead' perch) to locate the axle laterally? For those that know, would that reduce wobble? (I would think that it would, but don't know, hence the Q). FWIW bump steer was the first thing I thought of as well when I saw the drag link that far out of square.
i may be wrong, but i would yhink at the low of speed that it does this, the drag link may not play a part,i can go very slow 3-4 mph and hit a bump and watch the wheels look like jellie, if i was going faster,and the front end was darting from right to left i may blame it on the geometry of the drag link.... but what do i know...
What happens if you jack up just the left front corner (on the axle) till the right front is about to leave the ground, what do the front tires do? . Extreme I know, and I'm just askin.
Only if you have a cross steer set-up. If it is side steer, the axle will need to be drilled to install the So-Cal unit. That is what I did for my Dad's F-1 that had a wobble issue.
Bill, I hate to say, but I agree that the angle of the drag link and the steering geometry has allot to do with the wobble. If you look at allot of pictures of all types of cars running cowl steering the dragalink is very close if not paralell to the ground. Take a look at dragsters, sprint cars, and a good example is the Rolling bones cars, or Larrys 3W. Could you make a plate to bolt to your existing pitman arm to extend down so that the drag link would be paralell and then drive it around the block to see if it is better. As far as the Steering dampner goes, I agree they are great, but I dont think it will fix this. I put one on my sedan after driving it a while and it took care of an anoying small vibration around 65. It will cure a slight shimmy but not a slow speed death wobble. Good luck and I hope you get it whipped.
To respond to other posters as well. Flathead 31, You have engineering problems that must be dealt with, one at a time. You major emphasis is with the angle of the drag link. Until you get this link to operate somewhat parallel to the arc of the wishbone you are going to have steering/driveablity issues . This may go as far as relocating or changing the steering box. There may be some others but this is the main one to address right now. Ne**ussian: Use of a panard rod will not address the issues with the drag link angle and the installation of a dead perch is even dumber than a steering dampener. Gas pumper: Your dirt race car logic is wrong, these cars exhibit some low speed wheel shake due to exaggerated and unequal caster angles applied to the front wheels as well as the potential to have the axle skewed to induce handling characteristics for cornering. Even this wheel shimmy on a race car indicates that the setup is wacky. As for your random shimmy my approach would be to determine the square of the front end. Usually this random tracking is an event when one wheel is leading the other and the vehicle wants to steer to the heavier laden tire and the caster track makes it want go the other way so they fight each other. F&J: Hard to determine your issues with out a picture or description, if your car is shaking bad enough to crack something you have something seriously wrong. To answer you die hard steering shock absorber users. It is exceptionally difficult to address each and every application but it gets back to the track of the front end, the relationship of the offset of the wheels and the relationship between the wheel steering offset, the steering axis and kingpin angle. One thing overlooked is the effect of the alignment torque that is generated by the spinning wheel/tire unit and if the axle/spindle relation is not square, this dynamic creates a wiggle in the steering as each tire fights for true center and this wiggle is what the shock absorber will mask. Hope these answers put some more perspective on some wobble issues.
I disagree, a dampner is not designed to cure a higher speed wheel balance condition. It does prohibit whatever that "first little twitch" that gets a wobble going. Take a old VW bug and take the stock dampner off, and you will end up with instant death wobble. I was a vw dealership mechanic in the 70s, and a bad dampner was so easy to diagnose, as it instantly wobbled over bumps. But these VWs would still get a normal shimmy if the tires were unbalanced. I wondered about radical angled drag links myself, but looking at SO many 50's style trad 32's with f-100 boxes, those cars had severe angles downwards...and most don't run a dampner. Seems like cross-steered cars using a 40 box or vega, never wobble...or at least I have not heard of that so far here on hamb. If you read the orig death wobble thread, I posted all the tons of stuff my friend did to the 34. He was doing all the stuff suggested on that thread, as people would post ideas. Some things made a fraction of difference on when or where the wobble started, but it went away completely with the stock Mercedes dampner. The car is mint, no signs of anything being masked at all. His car got way violent IF you tried to brake, but as was mentioned, you could drive out of it if you have the nerve. On that 34, the one strange thing was: If you jack the front end up, and grab a wheel to turn it quickly from side-to-side, there was NO resistance at all. It seemed way too easy to turn compared to any other type of car or truck. This car has a mustang box and the link is dead parallel....and all centered and adjusted like **** mentioned above. On my build, I'd prefer not to have a dampner purely because it's visible on a highboy...so I am reading every post on the issue.
Yes, thanks, I didn't figure it would change the angle of his drag link. I was asking in general would a panhard bar or any other method of minimising or eliminating the potential lateral 'give' in the spring and shackles help reduce death wobble or the possiblity of it? It seems like it should .
****, Thanks for taking the time to respond with all th great information. I feel I have learned allot and I wasn't even asking a question.
I don't mean to be on this post all morning but to respond to F&J post #49. If your buddies car got a violent shake in the steering that was amplified during braking, then the axle is not in the car straight. The lighter leading wheel accepts the braking load quicker as the heavier laden wheel tries to catch up and induces the wobble.
Good tip. I am sure that he did not measure that. I'll try to get some input from him. Strange thing is that my old mopar roadster back in 1971 was parallel leafs that were stock, on a mint frame, yet that one was just as violent and also got worse with braking. You wouldn't think that axle type could get misaligned in the spring center pins, but who knows now.
That is screaming bump steer death wobble to me....every bump you hit is causing a little bump steer.
Death wobble is death wobble...any car can suffer from it for a mul***ude of reasons. Yes, I have fixed it on 4X4 conversions, slammed cars and trucks and stock set-up where front end damage was incurred. Replacing broken, worn or bent parts is usually the fix. With custom fabrications, "self-engineered" front ends are usually the culprit - secondary being mixmatched parts that create unrealistic steering, suspension and alignment situations. I still stand by my initial comments...a dampner will only MASK the underlying defect...period. The "talk is cheap" comment is pure BS when you have someone like **** here explaining exactly HOW to do it from an obvious experience and engineering perspective - NOT CHEAP - worth every penny because you paid nothing for expert knowleadge. SIMPLY PUT - death wobble is a sign of something wrong... out of whack. Fix it now or mask it and deal with future consequences. And here's a FREE opinion (yes, I have an a--hole too): JUST BECAUSE MANY PEOPLE ARE DOING IT...doesn't make it right. Just as MOST people aren't engineers, and MOST people should not be custom "designing" a front suspension that they expect to keep them safe at 70mph, I would guess that MOST people will throw in the towel and do the EASY fix... viola, a steering stabilizer/dampner. RV's do it PURELY because we drivers are not able to manhandle the multiple TONS of feedback that is forced upon the suspension and up through the steering system by such a huge vehicle under such a load on bumps and through turns. I the case of an RV it is a necessity and a precaution...not a band aid. ****, thanks for the info - you obviously know your s - - t!!
****, Thanks for the great info again also. When I was figuring mine out, one of the issues was the rear was 3/8" out of square. to the frame C/L and wheelbase. And it was like you said, it looked like the builder counted threads and put it together. And yeah, you're right on the race cars, And most evenrun excessive toe-out which dosen't help either. I didn't used to use toe-out, but a lot of guys did to help the car start the turn. I'm still wanting to try the greaseable spring shackles. Frank
I posted earlier that it was bump steer and that I'd go with a dampener as an easy fix. Looking at the pictures I don't think a dampener would stop it even as a band aid fix. You have some major geometry problems that have to be addressed. There is only one way to completely remove bump steer from beam axle type front suspension. That is to mount a rack and pinion type steering box directly to the axle. Then you would have a ton of steering shaft engineering to do. Not really an a feasible or eye appealing option. The best you can do is minimize every components effect on each other. Which would be things like making the drag link the same length and parallel to your wishbone. The parallel is possible but the equal length is not, unless you can come up with a attractive way to mount your cowl steering through the door. Basically every component needs to as close as possible travel in the same arcs as the other components. Even if you could get everything equal lengths once you turn the steering wheel the pivot points for the drag link have now moved, everything is traveling in different arcs and you have bump steer again. That is how the rack and pinion on the axle fixes it, all of the links travel with the axle so there are no arcs. What you have going on with your car is the "timing" of the arcs are out of sync with each other. For arguments sake you are only hitting bumps with your left front. You hit the bump and the axle goes up. The drag link is angled down, so as it goes up it is in sense getting longer. Your wishbones are level so as your hitting the bump their arc is pulling the axle backward ever so slightly essentially shortening the wheel base. This has just slightly turned the front wheels to the left. Now the front is returning to it's normal ride hight after the bump, which is turning the wheel back to the right, hence your wobble. To see just how much of effect this has on your car disconnect the drag link from the steering arm on the spindle then jack the left front only up. Now try to reattach the drag link without moving the pitman arm or steering arm on the spindle. The amount to misalignment is how much that bump would have steered your car. Bump steer is just one aspect of the geometry you then also have to get the caster, camber, and toe all correct also. **** pretty much has it down. It seems to me the first step would be to undo the changes to the steering arm on the spindle. Then to get a longer pitman arm that brings the drag link down to level. The longer pitman arm will increase the ratio of your steering because a quarter turn of the wheel is now moving the drag link farther. If your steering is then too quick for the street you'll have to move the box. After looking at the pics I think that these few changes plus a good alignment will fix the problem.
Have to say fellows, that I learned so much reading this post. **** and others obviously know what the hell they are speaking about. I have had a shimmy at 65 similar to Tracy, and have been trying to sort it out. I will surely be looking at all of things. Thanks so much for the great information.
I'm not sure i understand this? I installed the so-cal on my side steer by attaching one end to the frame and one end to the tie rod. Worked fine. Why did you need to drill? Just cursious...
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