Here's the list of things that need to be new or no play in them. The steering box, the drag link ends, the tierod ends, the wheel bearings, the wheels tires and hubcaps trued and dynamically balanced. If the car sets for a long time the tires get very out of round so drive long enough to let them get round again. A steering stabilizer on the tierod helps alot, toe in 1/8 in minimum maybe more.
Not "wear" stacking error of tolerances. Example a pin is .998" + or - .001 and a 1" bushing has the same tolerance. Ideally you have 2 thou clearance for grease. Now you get a 997 pin in a 1.001 hole and you have twice the clearance. Add to that the new busing was reamed that left grooves and high spots after 3 months of use those have smoothed out and give you another 1/2 thou. Get out the dial indicator you'll find stuff you can't see trying to wiggle it by hand.
I can go with that! That may explain why I had the problem with one truck. But the solution for the problem is still the same. Suspension system was in very good shape, with in specs, no wear detected, by normal means and alinement spot on, still have wobble. A little change in caster no problems after and no problems since, 20+ years. I have “ cured “ many , many cases of wobble that people claim could not be stopped! Folks have tried everything in the book, took their vehicles to several shops. After they have done that, I just take a few degrees caster out , their problem goes away. Just my experiences. Right, wrong or indifferent…..works for me and mine! Bones
Gotta think that if too much caster can cause the dreaded DW then there must be a lot of land speed cars that are in serious trouble, unless their record is under 30mph JW
It’s not the caster alone, it’s a combo of things , a perfect storm. When everything looks right, and you have an engineered front suspension, and you have the wobble…..something has to change! The wobble has plagued straight axles since the first ox cart! Like I mentioned , in my situation , the alinement guy told me to take some caster out, but I put some more in. But it stopped the wobble. The fix, was changing the castor, 2 degrees. I have been dealing with the wobble since 1957 and have solved many “ unfixable “ situations over the years. My main point in my post was even manufactured front ends in perfect shape and lined up perfectly, can still have the wobble! Trying to find the smoking gun on a homemade set up, could be fruitless! Bones
All it takes on a beam axle with parallel springs is for the springs to lose some set and flatten a bit and that will take some caster out. JW
It's a weird problem. Had flattened springs on my stock '28 Chevy, adjusted the steering box and put correction wedges in which stopped the car wandering all over the road. A few years later I put some NOS springs on all round without wedges and got DW at walking speed for the first time, had it a few more times since then!
A friend bought a freshly built 32 Roadster street rod that someone traded on a Corvette at the local GM dealer. Car had only a couple hundred km's and is very nice. A few years after owning it and cruising it around locally, it developed a death wobble at highway speeds when going over train tracks and the like. No front panhard with cross steer, and the 4-bar bushings had gotten just enough movement in them to allow the wobble. Put a panhard in and it drives perfectly again. Set it to what? A tech at an average alignment shop is going to know zero about what anything should be set to on an antiquated suspension design that isn't in his computer.
Caster is relationship axle to frame; so if rear tire height is changed to change frame rake, that will also effect caster. Right???? Slight change. Anyone have set of big & littles to check ( & the time & energy )?
I changed the rear shackle length on my pickup to lower it down slightly. That was enough of a change to alter how it drove, I changed the caster to get it back right again. Also when changing the caster I had to readjust the steering drag link to pull the steering wheel back to center. I never could get my steering box centered using factory springs and steering parts, not till I had drag link made I could adjust did the truck start driving right. As Amish Mike points outs, the caster changes anytime the rear is raised or lowered. It's the relationship of the axle angle to road, the frame to axle angle stays the same, but the road to axle becomes greater or less depending on which way the rear axle is moved. Going back to the three firetrucks, could the way they were loaded have been the problem with one not driving the same as the other two?
Joe, if you knew me back in my 33+years as Master Mechanic for the MFD, you woukd kniw my battle cry…”,Standardized ! “ lol Seven Chiefs grew weary hearing it. Since I was responsible for the specifications of all Fire Department equipment, I was able to get all Cummins engines, Hake pumps, Akron brass, Hearst rescue equipment( same stuff as the shifter) and Survair breathing apparatus! I am telling you this because I also equipped the pumpers as identical as possible. So , I would have to assume the trucks were loaded very close to each other! Bones
When you raised it you changed the caster. Even if you corrected it , to specks, you could have changed it and possibly eliminated the wobble. Bones
There was discussion earlier in the thread that if you went to a modern alignment shop, they would be able to give you a printout of the values and then you could adjust it yourself. Which is kind of nonsensical. On these simple old cars, you might as well do it yourself with simple tools, because there's no benefit to paying for a 4-wheel alignment on a vehicle the tech doesn't know how to adjust or what to adjust it to. Unless it's a hot rod shop, nobody is going to know what your caster and toe should be on something with a 100-year old suspension design.
I was the one who brought up a modern alignment. I simply was stating, if you can't find the problem, get to an alignment shop and see where the numbers fall. You don't need an expert at the shop, they just need to set the computers. Once you get the print out, take it or post it where someone who does know what they are looking at might see the problem. You are 100 correct, 95% of alignment shop couldn't fix it, and I wouldn't want them touching my stuff. But having a print out of all four wheels could be handy if you really struggling with an issue.
I'm not disputing the value of a Panhard bar to limit unwanted side-to-side axle movement, but I've been driving my car with a Vega box and cross steering for 15 years without one and have never experienced death wobble. Unfortunately, steering problems are often difficult to diagnose and as this thread suggests, many different things could be the source(s) of the problem.
The only thing that an alignment shop can do is take your money . The only thing adjustable is caster & toe , you can do that at home , numbers dont mean shit , getting the car to drive properly , whether it's 2* or 12* , 1/8" in or out , who cares . It's a game of trial & error , move on. !
spot on, and way quicker than pulling all the wheels , putting it on a plate and measuring the inter sections...
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