Hot Rods yet another Model A "death wobble thread

Searched the hundred plus threads on "death wobble". Got a few ideas i'm going to try.

Here's the descpription of what's happening, then i'll give my solution possiblities. Let me know if i've missed anything.

LOW SPEED shaking, side to side (not up an down bounce). I had about 2* caster when I built the car (which resulted in poor handling), so recently I piecut the bones a bit more and ended up with about 10*. Driving out here in "middle of nowhere" where i live is fine, even with little bumps. While in a city it is terrible. It happened once a couple months ago in Canton and again this weekend while i was visting with the model A.

When accelerating quite quickly there is no problem. When above roughly 35 mph there is no problem. Normal/slow acceleration, driving under 35mph, will produce a death wobble when hitting a bump in the road, a pothole, etc. and especially something like train tracks. Open road, bumps or not, no problems. Once the wobble starts, the only way to stop is braking to almost stopping, or accelerating above 35 mph as mentioned.

As other threads i've read have asked; i'm running about 20-25 psi in the tires, I have split wishbones, spring above axle, bias ply tires. 56 ford F-100 box.

I'm thinking the following may be the culprit: too much caster? Again, i never had the shakes when i was running less caster. This is the only thing i've done differently. I recall reading that my toe-in may be off after gaining more caster, is that correct? My steering box is still tight. I also doubt that my kingpins/bushings are worn excessively. It's a 5 year old build, yes, but realistically it is not driven that much.

Another thread mentioned ***uring the axle is square with the frame. Will measure this and everything else tomorrow. I piecut the bones behind my original piecut, by about 4 inches to clear my tie rod. Does that cut placement matter? I figured it wouldn't because the bones are directing the caster angle of the axle, and shouldn't matter where the pie cut was made. I could be wrong.

Plan on tightening everything again, just to make sure nothing is loose. my dad's model A did the same thing a year ago and a simple re-tightening took care of the problem.

Any other suggestions i may have missed is appreciated.

Thanks
-ace

 

i chased this problem, for awhile. mine turned out to be, of all things a tire issue, and the fix was that i moved the front tires to the back, no more problem

 

Im running a 29 Dodge on a 29 A frame, had all the same happen to me.
Found a lot of stuff on here about it. why it happens, what to try, and on it goes.
Long story short, and a lot of blokes will tell you it`s a " band-aid " fix, but it worked for me, is a steering damper from a VW bug.
It `s fitted under the car, and it dates back to the early 50`s. The thing that sold me was, the bug was fitted with it from the factory, take it off and the
thing get`s the shakes. one of the 3 most top selling model`s of car in all times, The Bug,,,
It worked for me, fitted it 3 years back, never had a wobble since. and all for
less than $30. Martin.

 

plus one on above^^^^^^^but in my case....

panhard bar mounted ladderally from axle to front crossmember . this took care of my death wobble .

 

Had the same problem on my roadster, ended up being a tierod end.

 

So far today, we adjusted the toe-in. After giving myself more caster apparently the toe-in was actually toe-out, now. We readjusted and set it to about 1/4". I tightened all the tie-rod ends from the wishbones, draglink, pitman arm, etc. We also determined the axle was 3/16" inch off square from the frame. After adjusting this we measured the caster angle, which is now 9*.

It seems better. I drove it over some tracks at a slow speed and there was no wobble. I may move my wishbone's rear brackets vertically on the frame to give myself 7* of caster, not 9 like i have now. Is the general consensus between 4 and 7? I've read that, or 5-10. However, a lot of threads i've read say that over 9* is too much. So, how much really is too much.

i'm still not 100% sure that the problem is gone. Feels better so far. We'll see!

 

Ditto what Martin said. My Model A got the same shakes after about three years on the road. F-1 pickup st/box, undropped '35 axle, spring over axle, split w/bones, '46 spindles, F-100 brakes, 6.00 x 16" tyres on stock rims (offset not modified) running 24 p.s.i., I have about 7 - 8 degrees castor and about an eighth of toe in. It would seem after all the tie rod ends and kingpins 'bedded in' and loosened up that the wobbles began. I put on the Krautwagen dampengeshaften and no problem in the last 12 years.

 

O/T hint - to make the degree icon °, just do (ALT)248 at same time, then you don't have to keep putting in asterisks.

 

° cool, thanks! I never knew that!

 

On a Mac degree˚ is Option K. But who can really remember that. I just spent the last 3 min figuring it out.

I get the wheel shimmy too, but only occasionally at 10 mph on bumpy roads. I have worn parts I need to replace.

 

1/4 " toe is too much especially with bias tires 1/16 to 1/8 is more in the ballpark.

 

" krautwagen dampengeshaften" now thats funny

 

I checked everything on the front end and put new tires and continued to have problems. Finally sent the 16" wire wheels to Woody's Wheel Works in Denver as a last resort. Seems both wheels had serious flat spots and were not true. Waiting for the wheels to come back from the powder coating shop before I can check it out. At $495 a pop (if you can even get them) repro 16" wire wheels make the case for taking care of originals.

 

I'll bet she looks funny with the big's on the front and the little's on the back....

 

Thanks for that AJ - everything is several ˚˚˚ simpler on a Mac.

Back to the original problem, did you check your kingpins for wear? That was the problem on my stocker.

 

New rule: Every death wobble thread from here on in MUST contain photo of your front end.

 

thanks for the replies. especially the degrees icon. i'm on a laptop so alt248 won't work!

Zombie- i'll work on it.

Kingpins are good. Also, the wheels/tires are fine. As i mentioned i didn't have the problem until i gave myself a few more degrees of caster. This is what leads me to believe the problem is with the caster. I'm working on it later today.

 

X2...skip the old way of 7-8, go at least 4-5?

 

i really hope i dont run into this on my A

 

I would start with the toe in/ toe out, it's the easiest to fix.

I always start by checking the simplest/ most obvious and work my way up to the harder stuff to fix, hoping that it'll be something easy.

 

I had this problem on my '34 pickup. All new parts to begin with, played with toe settings, different caster settings, tire pressure, replaced perfectly good parts, checked camber angles, panhard bar installed, etc... Finally gave up and installed the ol' vdub steering dampener up under the front crossmember and out of sight... never had the problem again...

 

yeah, i hear a lot of using der volkswagen dampenerdenger or whatever it was called .

I would like to try and solve it without that first. Hundreds if not thousands of hotrods "back then" were just fine without. If need be, i'll invest.

Zombie- I agree, simple is by far easier! I reset the toe-in, and this afternoon i was able to screw my tie rod ends in a bit further which results in less caster. I am now down to 8 degrees caster. I still have more to go, but i need to move my brackets up higher on the frame to accomplish that. I always wanted to re-do them anyhow, just for looks.

So, what degree should i shoot for? i'm thinking in the neighborhood of 7 or less. Any thoughts?

 

I think the general consensus is on here is 5 degrees to 7 degrees with most leaning toward 7. We used to do 5 degrees all the time back in the day. I think the 7 degrees got started when ch***is builders started tipping back the front crossmembers to 7 degrees to make up for rubber rake. Too much caster tends to make the steering heavy in sharp turns...

 

That's what i was thinking. I'll go for 7, if i come up a degree short that's OK. With my 10 degrees i don't really notice too much heavy turning. we'll see how it goes...