Technical Caster Adjustment on Straight Axle Frontend

Checked kingpins? Some movement in em will cause this. And bias are a terror cold and feel like they are square wheels for a bit until they get some heat in em. 6-7 degrees is perfect for front end geometry. I've ran 12 in my 56 pickup and was nice up to 120 my model a has 6.5 and is smooth and clear to 120. Hell those tires could have a road force issue causing it.

 

The scrub is really leverage ratio,load on spindel/hub an steering arms{ not often thought of that way] . Drawing a line down through the kingpin to the road X,as long as that point X comes with in about 1 in. of contact patch{ out side off}
of tread to road. That's close enough,don't really have to be inside contact patch. But that's about limet of outset/offset. There is another thing I see too much on rods,and that's front tires too wide{also too many lbs.} that add a lot of prob. even more so if shocks are crappy. A temp farmer fix,is too tow out the front 3/8 to 1/2in.=its stops the low speed wabbles on most rods, at the cost of high tire edge wear{ note said * temp,tell right fix].

 

I know and understand a lot of people don't like the "Band-Aid" of the steering dampener shock on the tie rod. But if you're around 7 degrees, all mechanical parts are in good shape, steering box tight, good tires (I prefer radials, I also understand not everyone's taste), the dampener has totally taken care of two cars that I've been very personally involved with. And although I did and would try everything else first, I would not hesitate to put one on to take care of the problem. Just my experience.

 

I no longer see the drag link in picture 3. Ideal is to have the drag link and the bones the same length if the drag link is a lot shorter it san cause bump steer leading to wooble

 

I have radials and had a wobble at 55 to 60 with 30 psi .
I rotated the wheel on the axle one lug thinking maybe the drum and wheel were out of sinc and lowered the air to 25 psi . Seems to be gone .
My caster is set at 7
Just my 2 cents

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Wow...didn't notice the slotted axle!

 

was gunna say it earlier on ................. that sure is one scary axle

 

Here's another thought that I'm wondering may contribute to woble. The steering arms on my spindles have been bent downward due to the dropped axle. They are bent in such a way that the effective distance between the king pin and the tie rod end hole is cut in half. The normal length of the steering arm is about 4 inches. The effective length of mine is about 2 inches as a result of the radical bend. My thoughts are that arms have less leverage from wheel to wheel and therefore have less resistance to fight wooble. This is the way I acquired the front end. When I've set up dropped axle frontends in the past, I would keep the steering arms length stock and put the tierod OVER the wishbones and put the tierod in from the top of the steering arm.

 

"Ideal is to have the drag link and the bones the same length if the drag link is a lot shorter it can cause bump steer leading to wooble" . . .

. . . and they should be mostly parallel -- can't see in your photos.

Are you mixing radials with the front bias? Can't see by the photos. I drove the sedan pictured from Bonneville to Southern California with that mix once -- scary all the way.

Some times we have to realize that cars were driven thousands of miles a year with 6 volts and bias tires. Something's wrong.

 

Marty has the starting point, well spotted! Good chance there will be evidence if cracks in the chrome, a very strong magnifying glass is order.

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Drag link is much shorter, but if I were to drawn line through the drag link backward, it would closely intersect the wishbones rear pivot.

 

I personally, would give that axle to a "gasser" goin' into a museum.
I WOULD grind the top of new axle at the spring eyes, so the shackles had some room to dance..
I Never liked those oval cuts in the axles.
Lotta gasser did that, and would shake at low speed.

 

Every time the suspension cycles the front spring pushes against the axle. Might as well be a rigid frame, suspension is probably the give in the sidewall of the front tyres. I'm surprised nothing has broken so far. How much compression is left in the shocks, you might have to shorten the link?

 

I agree,
and I think I see a spring leaf UNDER the main spring leaf that has the spring eye. What's THAT doing there? Get it out of there..!!!! So it will have some room for shackle to work...

Also take the "dogbone" link OUT and attach shock to stock perch. OR because its fender-less, you could make bracket and raise shock housing up, so shock arm is parallel with frame.. (maybe easier)

Might have to notch frame for spring leaf clearance.. (typically )

 

Didn't have my glasses on, going blind

 

Can you elaborate?

 

if the drag link and radius rod are not aligned with the same pivot point, It will cause "bump steer"

draw a picture.
or google: "bump steer explained" Its all there for you.. !!!

 

Tires. Rotate tire on the rim and re balance. Tire pressure too. Tires are the biggest cause of the death wobble. Do you know anyone that you can borrow a pair of wheels and tires to test?


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When you hit a bump or pot hole and the axle moves up or down the axle pivotes around the anchor point of the bones. If the drag link is longer or shorter than the bones it will move in a different ark causing the wheel to move in or out.

 

good explanation about the arc....

 

Holy cow, I didn't notice that either!

 

Drop your tire pressure to 18-20psi and try that.

 

Oh dear....

 

It also appears that there is a washer underneath the axle between the axle perch boss and the fork on the front end of the radius rod, like maybe it's taking up some excess width in the fork because the opening is wider than the axle perch boss.
Moving this washer to the top of axle would move the perch bolt up, giving more room for the spring eye.

 

HA! Good eye, Dave! (missed that one myself...Axle specs must be for '32-'34, 2" at the wishbone bosses) '35-'40 wishbones are 2-1/4" hence, the washers; Just that distance plus the 'extra overriding leaf' that is wrapping around the reversed eye would certainly minimize any 'shackle swing room' needed there!

 

And...make the angle of the shock arm even worse! I know it wouldn't be much, but all this shit is dominoes that just keep knocking into one another.

It's also why it's so hard to really assess something without actually being there.

 

Mike, I think you are mistaken, Ford axles 32-36 are 2".

 

Shootin' from the lip again:
seems to me the tie rod is awfully close to the radius rod, and
as the wheels turn the tie will rise depending on the direction you are turning.

as I see the one picture the tires are straight and tie rod is very close. turn steering wheel while watching tie rod hit bottom of radius rod..? no?

 

There is NO additional leaf. You're seeing an optical illusion from a fuzzy photo. It's a single main leaf with reversed eyes. Also, although it's unable to be seen in photo from this angle, there is almost 1/2" space between the sring eye and the axle.

 

There is NO additional leaf. You're seeing an optical illusion from a fuzzy photo. It's a single main leaf with reversed eyes. Also, although it's unable to be seen in photo from this angle, there is almost 1/2" space between the sring eye and the axle.