Computers are very sensitive to " garbage in - garbage out . IMO there's nothing much useable between modern suspension specs & straight axle technology .
You said you set the caster at 10 degrees the first time and claim this was the issue, i doubt it as on my Belly Tank build i set it at 12 degrees and most cars like this have 20 degrees as a base point so i can't see how your 10 degrees could have caused the issue, toe out yes, shackle oscillation using the drag link as its pivot point yes, worn perch bolts or/ the axle bores are also a very common cause. JW
Face it everything from the steering wheel to the tires & everything in between is a possible cause of DW , with the rest of the chassis offering further possibilities .
Need to fix that negative toe in! It should be 1/8" positive toe in, and likely why you had Death Wobble. My short 89" wheelbase Austin gasser has 11 degree caster, and never has had any death wobble or ill handling, but I run 1/4" positive toe in.
The owner can do the same with tape measures and digital angle finders at home. A car with a straight front and rear axle doesn't need to go on an alignment rack, and most modern-day techs wouldn't even know where to start on adjusting anything if they had to (part of the job of a wheel alignment). The computer printout turns into a very expensive and pointless piece of paper.
it didn't say I had to make my reply for everyone, nor did he say no one else could reply...lol any way... hope all is well..
I think maybe a misunderstanding of terms. I had always thought that leaning a front axle back was negative and vice versa. It made sense in my mind at the time But I agree, toe in or toe out.
Depends if you use the words in or out along with toe. Positive toe = toe in Negative toe = toe out You just don’t combine all those words, choose your lane and be consistent.
With model A’s with stock suspension, most of the time it’s the ball on the end of the wishbone. Sometimes it is worse where someone used the rubber ball that is sold to tighten up the ball. It deteriorates and the death wobble is worse.
Sort of related to this, who can forget the infamous "deth wobbel" thread https://www.jalopyjournal.com/forum/threads/stell-got-my-deth-wobbel.470139/
I didn't mention the ball because he said he's got a V8 and that generally means the wishbone has been split. The rubber ball was one of those band-aid patches that lasted just long enough to sell the car.
“ Wobble is caused by loose parts” not necessarily! I have told this story before about my experience. I maintained a fleet of vehicles with straight axles for 33 +years. Granted they were trucks , but straight axles are straight axles! We purchased 3 identical Firetrucks made 1,2,3 on the assembly line. After about three months one of the engines, I will call it #2, developed “ death wobble “ when hitting a set of tracks in the middle of town! So I pulled it in to inspect for loose parts. I found none, so I took it to my “ go to” alinement shop. Spot on! Perfect alignment! So I pull in engine #3 and swapped front wheels and tires! The problem stayed with #2! So, no loose parts, perfect alignment, proved it wasn’t the wheels and tires! But still had wobble! I go to the old guy at my alignment shop and ask him for help , I have an engine out of service and I can’t fix it! He hands me some 2 degree shims and tells me to put them under the axle! I do and the problem goes away! I went back and told him thanks! That 2 degrees more castor did the trick! He jumped on me and told me he wanted me to take 2 degree out! But what I did cured the problem! Three identical new straight factory axles, in identical shape and one wobbles and two don’t! My point is, you cannot always find the smoking gun on a wobble. Make sure all parts are tight, alinement is correct, tires are balanced and round and true. This is assuming the front end is designed properly! So, if everything is right, you can still have wobble! If you encounter this , a change in castor could solve your problems. Just my experiences! Bones
Not 3 "identical". Nope - one was bad. It had that combo of parts that after only 3 months of wear it was at the outer limit of tolerance and caused a problem. Adding the shims tipped the axle enough to change the dynamic load on the parts to hide the problem.
I have had death wobble (hit bump at 10mph and front end shakes until you stop) on 2 different cars. Both times problem was solved by removing a couple of degrees of caster.
i bet its because when you change the castor angle you are in effect loading the spring with energy in a twisting fashion. at stand still it has energy in it due to weight upon it and the 10 newtons \/ it is wound and twisted when driving, when the car for what ever reason becomes lighter in the front the energy is released IF and when you remove the cheap nylon shackle bushesyou will notice they are worn into a triangle shape - or thw eare is a triangle shape, which is indicative of the spring twisting about its natural centre - line
you can put more camber and more caster in a beam axel that and with 4 wheel alignment you can see where the rear correlates with the front, I would put the car on a plate and check for diamond also that would tell you if the axels are square... but like said... all can be done with a degree wheel tape measure and level...
The center line through the shackles changes constantly following the contours of the road, up and down and i know you must have it centered at static. JW
Yes it does, as the wishbone (spit or not) travels in an arc and for the most part the spring does not. JW
I'd say that's the opposite of my thinking. Tires toed in would be positive, and toed out would be negative. But really they're either toe in or toe out, so as long as yours are toe in 1/8" they're fine.
The problem has stayed hidden for over twenty years and is still hiding! I find it hard to believe very much wear occurred in 3 month on a Fire engine. When I took it in to a professional alinement shop they could not find any wear! Bones
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