I just picked up a '27 roadster on a deuce ch***is. Got the drivetrain together and drove it home for the first trip last night. While coming down my street I stayed slow but hit a few bumps(connecticut roads ****) and the front wheels went into a convulsive shake. Imediatley I slowed down thinking something broke/came loose but while slowing down the shake stopped. I pulled into my driveway and checked it over to find nothing wrong. I drove it back to work this morning with no shake. Pretty basic set up too, stock I-beam,split bones with spring mounted behind axle, what appears to be a corvair box? basically in the stock '32 spot on the rail. It steers and handles pretty tight and last owner claims most ft end parts are new and do appear to be. Any suggestions ? Never had a shake quite like this.
I had a '53 Chevy pick up that did that. Turned out to be a worn pittman shaft bushings in the steering box. I'd hit a hard bump at around 40 mph and if you whet faster it would shake faster. I'd have to slow to about 15 mph before it would stop.
i had a similar problem on my coupe. Make sure your U bolt plate that holds the front spring tight in the crossmember isnt bottoming out on the crossmember before it has a chance to hold that spring pack nice and tight. That was my problem. if your hitting the crossmember before the spring is fully tight your gonna have a pretty loose spring.
Here's the link.....READ IT http://www.jalopyjournal.com/forum/showthread.php?t=258945&highlight=wobble Yes, It's long, but read it
Check for excessive caster (lean back of the axle) we just cured a similar thing by reducing the caster to 6 degrees .Was going to put a damper but saw that as a band-aid to a certain degree .Rod in question had 11 degrees & a light front end.
I have cured that problem on 2 cars by reducing caster. It goes without saying that all components should be in good shape and adjusted properly.
I agree much on the caster. Too much is BAD. You need shocks, too, esp. if sprung properly (soft IS proper). But, check the tire pressure, too. I found mine would 'walk' with low tire pressure, which is hard to see just by sidewall deflection. You want around 30 psi. Cosmo
If you have a Corvair box is the steering side link. I had a very similar problem with my roadster and it was the connection to the steering arm on the steering box. I changed it to make it stiffer and the problem went away. I also agree with to much caster, 6 degrees is about right. Rex
This is a repost of the last time this issue was discussed. <!-- icon and ***le --> Re: death wobble? <hr style="color: rgb(153, 153, 153);" size="1"> <!-- / icon and ***le --> <!-- message --> 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 <!-- / message --> <!-- edit note --> <hr style="color: rgb(153, 153, 153);" size="1">
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