Loud Thud
 

When my Model "A" hits a pot hole in the road with just one wheel, it makes an extraordinary loud thud noise in the front suspension, and it is felt in the steering.

The car has less than 5000 miles on it since a total restoration. What say you about possible causes of the thud noise?

Re: Loud Thud
 

Have you checked that everything on the front suspension that should be tight, is actually as tight as it should be? U bolts that hold the front spring to the crossmember? Spring perch nuts? Steering box to frame? Etc, etc

Re: Loud Thud
 

Maybe take a look at the front radius rod ball socket to check if there is too much play?

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When you say it's felt in the steering, is the wheel trying to move, or do you just have a sensation of impact? Do you feel it on the floorboards?

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Check everything under there for tightness. Something was probably left loose.

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I experienced the same thing Bob did. I found that the rubber ball on the front radius rod was shot. I replaced it and the difference was like night and day.
Marty

Re: Loud Thud
 

Seems like that would mean there must be a shock to that part of the frame, which is transmitted to the column. Either a part of the suspension is hitting the frame or the shock absorber is locked up and transmitting the motion of the axle directly to the frame.

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Also jack up the front end and see if there is any vertical play in the wheel which would check for a king pin issue.

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If it was the rubber ball, How would one going about repairing or replacing with an original steel ball?

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The steel ball is inside the rubber ball.

Paul in CT

Re: Loud Thud
 

The radius cap assembly is different for the rubber ball, so step 1 is procuring an original-style cap assembly. Step 2 is you can either cut off the current ball and weld on a replacement, or, if the ball is still close to round, you can shim it with a concave washer.

Re: Loud Thud
 

I would say that the loud noise and reaction at the steering wheel is from hitting the pot hole. (Sorry, best I could come up with.)

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Re: Loud Thud
 

Are your shocks working and adjusted? Maybe there is no damping or the shock is locked up? Just a couple more thoughts. If it is a pothole, the wheel is falling into the hole then hitting the other side of the hole so maybe your shock is too stiff (or not moving) in compression. Check to see of your shock arm is tight on the shaft.

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It may be prudent to tack weld the concave washer to the top plate of the stock clamp assembly because the washer can shift . This would also help keep the camber in the 3 -4 degree range. Also the drag link and tie rod ends may need adjustment for the 25 % spring length compression.

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While the Model A is obviously no independent front suspension, the axle will still move a lot more on the one side than the other. It can move all the components like the shock absorbers on the one side independently from the other and the radius rod or wishbone does allow for quit a bit of twist or roll around the ball axis. Sometimes the spring eye makes contact with the axle but I don't know if that is happening in this case. Most of the time that is due to springs that are in need of re-arching or a lot of wear in the shackle components but it can happen in some cases.

Re: Loud Thud
 

The loud "thud" is likely the radius ball pushing the socket assembly apart and the sound occurs when the socket reaches its limit.

The lower part of the socket is held against the ball by spring pressure. When the front drops into a pothole, and then climbs out, there is a tremendous amount of force being transmitted back to the radius ball and socket. The ball will try to move backwards and as it does the lower half of the assembly (moveable) fully collapses the springs and the nuts stop the movement. This will cause a pretty robust momentary force against the bellhousing and the resulting sound.

A full size and round ball will make the noise to a lesser amount. A worn ball will make more noise because the movement is greater within the socket. Just my observation.

Feeling it in the steering...Yes the movement described will place some momentary pressure on the pitman arm and that is felt in the steering wheel.

I heard this sound many times while driving parts of Route 66 in 2013 with my Phaeton. The old road was rough.

Good Day!

Re: Loud Thud
 

Hey Bob,
In my experience, Dave in Mn has correctly described that your problem emanates from radius rod ....ball !