Technical Bump steer? But not really. Truck feels.......weird

You alter the drag link so as to mimic the original inclination of the rod ends.

Here is a rather crude drawing for you. Sorry my design software is on my other computer and Micro Soft paint is hard to work with. But it should give you some idea what I am talking about.

 

Nice work, Benno. You have just given away an inch in overall length!

 

Most of us can't afford to loose an inch!

 

That diagram of the drag link is misleading. It will not have any beneficial effect on a bump steer situation. The geometry is based on the relative height and projected travel of the balls in the tie rods. The shape of the link is immaterial, although the straighter the better for rigidity.

What it will do, possibly is improve the angle of the pin relative to the body of the tie rod end.

That is why some stock drag links do have a kink; to optimise the angularity of the pin in the tie rod end.

I improved the steering on my 33 by lowering the steering arm when I fitted the dropped axle. It had bump steer and I got rid of it by lowering the arm.

Mart.

 

I'm not z-ing my link.
Dropping the arm should be sufficient.
I'm also ordering caster shims today.
My weekends are filled with girl scout stuff, so I'm not sure when I'll be able to post the results.

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Both my panel trucks with straight axles benefited from 4-6 deg shims. They're at stock height, but liked to wonder, not return to center easy and I was constantly correcting to stay in a lane after a turn. I personally didn't like the F100 p/s setup on my '54 (Toyota 4x4 box, Ford pump), it was over powered. I ended up putting a regulator on it, dialing it way down and adding caster shims.

 

My Lincoln came from the factory with cross link shaped like B in the diagram above. High point is on steering box end, low on right spindle.

 

You can go either way with it. Cross steer is different to set up but the principle is basically the same.

One of the things that we seem to forget is the imaginary line that we draw through the ends of the drag link and the rear pivot point of the spring. On a cross leaf the rear pivot point is the radius rod (or hair pin) on parallel links it is the rear anchor of the spring. If you have a factory setup already that you have changed the axle location all you have to do it mimic what you started with. Up or down on the front axle is the same just turning your drag link in a different direction.

But it is what it is I guess.

 

This is from a 1937 Chevrolet Engineering manual. Shows the difference between '36 and '37. It explains the different paths the drag link and axle take. Bump steer, the farther apart the path, the more bump steer you get.

 

Interesting to see what Chevy did to address a bump steer issue. Bet the 37s drove better than the 36s.

 

When you install a drop axle in a parallel front spring front end, you increase the leverage that the spindle along with the tire and wheel have to twist the spring when hitting a bump. De arching the spring and making it flat actually helps with the deflection or spring wind up. That is probably why the spring was broken on the passenger side. You can see how the spring windup can alter your caster and cause havoc with your steering in the first drawing. The second drawing shows a solution to the problem. A stiffer front shock would also help.

 

I see in the last post the first picture is labeled “wheel-hop” which I am assuming is originally for a rear axle (originating from the pinion gear climbing the ring gear). Then used to show how an extended distance from axle pad to spindle centerline flexes the spring during braking and forces rearward in the front wheel(s). Correct? Interesting picture on the additional leaf section put on the front spring pack to help with this situation. Never seen that before.


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Sorry to burst your bubble here, but that is wrong!
A link [or arm] is an imaginery straight line between 2 pivot points.
It wouldn't matter if it was straight, "S" , or "J" shaped.

Racers use J shaped panhard bars to clear quick change rear ends. It behaves exactly the same except the structural integrity is compromised.
Bending a bar can prevent ball joints binding at the end of travel

 

I am so sorry that you have totally missed the point of what I am trying to say. But whatever makes you happy tickles me plumb to death.

 

I'm with Kerry , the only thing altering the shape of the rod does is correct the ball stud alignment & weaken the link , does nothing g to correct bump- steer ( if that's what you're trying to say ?)

 

Please enlighten me....... what did I miss.

Understand with a side steer any mechanical bump steer can only be minimalized with the steering straight ahead [which is when you don't want it]
As soon as the pitman arm arcs , the geometry changes

Unless the pitman arm balljoint is directly adjacent to the spring eye, the bump steer corrections can only be reduced [the drag link and spring rotate on different arcs due to lengths being different]

All the OP needs to do is sit the vehicle on a stand [at ride height] with a wheel removed.
Then mark crosses on all the ball joint centres + the centre of the spring eye.
Then use a string line to eyeball it .

A string line can be moved up or down [pivoting from the spring eye] through the pitman pivot to get the height of the steering arm [which can be corrected with heat]

 

Go back to this chart for shock placement. With yours laid over, they are only working 60% to 70% of what they could be doing.

 

I had the shocks at a really low angle on my glass 34 coupe and when my mate saw them he said "Ah! Panhard shocks!", which I thought was quite witty.

 

Ok. Installed some 6 degree shims. If my math is right, I subtract the angle of my driveway (about 4 degrees) frome the total caster (about 10 degrees) which gives me six degrees of caster.
Which means I had 0 degrees before? Yikes!
I have not dropped my steering arm yet because I need to ask Sid a couple questions before I commit.

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Heated and bent my steering arm today. Looks like my stock drag link is about an inch too long now (roughly).
It'll do for now until I can cobble an adjustable one.
This already seems like it will help.
Next step is a steering box rebuild and the drag link. Then we should be in business.

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Mucho better.
I'll test it out tomorrow and update.
This is what happens when you trust a prrevious owner's skills.

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what is that contraption on the tie rod end?

 

It drops it to compensate for the drop in the axle.

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Please see your springs is there a different leaf on the passenger side . I don't think you can mix and match leaf springs One side looks like it has two buttons and the other side does not.

 

The spring shop replaced the broken leaf on the passenger side. He said the buttons are for sliders and won't have any effect on one leaf.
So far it seems ok, and he's been doing springs for over 50 years.
Charriot Spring in Fontana, Ca. Cool old guy. Mostly does heavy truck stuff.

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Took it out to a club function today. Night and day difference. I can hit bumps at speed and it sails through em.
I do notice the sloppy box and too long drag link, so that's next on the list.
Only bummer is that the caster shim raised it back up about 1/2", but that's not so bad.

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Glad you were able to make an improvement. At least now it is driveable. The steering box and drag link will now come under the heading of improvements rather than "fixes".

Mart.

 

Exactly.
I'm trying to nurse this thing through while I get my 39 on the road.
So far that means I'm constantl fixing the truck and not the 39.

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Jeez I fat fingered that, didn't I?

fixed it now.