1940 Roadmaster shimmy

[Drakeule]

I took the 1940 RM out for the first time today. Everything felt OK, except I got a significant shimmy at approx. 20-25 MPH. I appeared to iron out above this speed.

At first, I thought a tire had gone flat;but that was not the case. I guess we can rule out a bent rim (?) Bad alignment would present at most speeds, correct?

 

Interested in any and all input.

 

Thanks in advance,

CD

[Matt Harwood]

Death wobble is almost always kingpins. There are tricks that can be done to make it better without necessarily replacing the kingpins, but they'll eventually need to be replaced no matter what you do. It's a medium difficulty job.

[old-tank]

If it started suddenly, look for a broken spring in the drag link (center link).

[Kenneth Carr]

If it is kingpins as Matt mentioned, the socket for the kingpin is likely to be out of round and will require shims to

make the new pin fit. That had to be done on my '41 Roadmaster.

[Drakeule]

Roadmaster 71: that brings up and interesting point. I've read elsewhere that you can just shim the king pins; so why replace them if you would have to shim them anyways?

Does anybody have know how on just how to shim them? They mentioned using feeler gauge stock. Inquiring minds want to know! 

[Larry Schramm]

From my experience, "death wobble" usually happens from about 1-2 MPH to about 10 MPH.   I have never had it at 20-25 mph on any of my cars.  The best thing is to take the front end apart and check everything for wear and fix what is worn. I just did that on my 1913 Buick. Fixed most of it.  I can still get it once in a while, but I believe it is now tires.  You can check the lateral run out of both the tires and rims with a good dial indicator.  Run out on good tires is usually less than .040"

 

Be sure you have the correct amount of caster in the front end and the correct amount of toe-in.

Edited June 14, 2022 by Larry Schramm (see edit history)

[Kenneth Carr]

Regarding Larry’s comment: My ‘41 would jerk suddenly left or right every time I went over an imperfection in the road. I had bias ply tires.  Very scary.

I had the kingpins, tie rod ends, stabilizers,  bad A-arm, springs, bushings, and rubber bumpers all replaced. Then a good electronic alignment.

Now I have control of the car and can cruise easily at the 45 mph limit on curvy local roads. Still have the old bias ply tires but they don’t get me rattled any more.

 

Ken Carr

Edited June 22, 2022 by Roadmaster71
added name (see edit history)