Hot Rods issue to cause a death Wobble

I'd buy the tires being the issue (separated, out of round, etc.), or the alignment, but not the difference in tire sizes. A lot of guys are running a lot more rubber rake than that (I'm planning to as well) without issue.

Again you gave us little information, but the difference between front and rear tire sizes isn't why you had death wobble, if you changed your tires and corrected the problem it wasn't the difference in sizes that were to blame. You accidentally fixed the actual cause in the process.

 

Yeah, plenty of hot rods with a big difference in tire sizes that drive just great. The tire size is not the cause of your problem.

 

I run the same tire sizes with no issues. I changed the leaf springs, front went down, steering got loose, I changed the caster ( gave it one more degree ), it drives right again.
No wobble at anytime. Caster or lack of it, made the steering loose, couldn't drive a straight line without a lot of input at the steering wheel.

 

Not much you can do for camber on a solid beam axle, and it requires bending the axle to do it. I've never had a solid axle ever need camber adjustment myself. Caster and toe in have always made them wobble free for my builds.
Both of my g***ers have huge differences in tire size front to rear, and never had death wobble at any speeds. Even runs down the dragstrip at over 100 mph didn't result in death wobble. Last time I had a car with death wobble was in 1968 when I built my first '57 Chev g***er and was clueless about toe in or kingpin angles. Once I got both set it drove great, and no more death wobble or wandering all over. Lost track of how many straight axle conversions I've done for guys over the last 55 years with no problems.

 

Has the car always been set up this way, or has something changed, eg tire sizes? It may have previously been OK but marginal, and a first change pushed it over the edge.

I bought a 32 that drove great, or so I thought! I soon found an incredible shake at around 50mph that I couldn't even power through. Not knowing about live axled cars at the time I was at a loss. I eventually found m***ive bind in the spring due to misalignment of axle and spring. Self aligning perches sorted that and most of the shake was gone. Getting the shackles in was a struggle though. I subsequently learned that it should all go together with minimal persuasion so reinvestigated. Caster was wrong and the 4 bar lengths wrong too. Fixed all that and found the self aligning perches were unnecessary! Drove great after that. 30 something years later and I still have the car but the 4 bar is replaced with hairpins.

Chris

 

For a problem that has been "beat to death", I am not seeing much science. Mostly anecdotal evidence. Someone must have done a proper deep dive on this. Bonneville guys?? I see a book on Amazon "Dynamics of High-Speed Vehicles". Anyone read it? Is it worth $55?

 

You can do that deep dive and tell us if it’s worth it.

 

And after all that , solutions on the net are far & wide & at best , a guess ..

 

I took all the caster out of the 27 and it stopped the wobble but would “ hunt”. Drove it like this till I could afford new spindles.