Hey chassis boys... 1.5 degree difference in king pin inclination left to right?

[Lee_in_KC]

So I was out tweaking on my caster still trying to eliminate a death wobble, and for the first time since I built the car in 2005, I compared the left king pin inclination to the right. The left has 1.5 degrees less inclination than the right. At first I was shocked, then I thought maybe this is not that unusual. So is it? The axle is a Superbell tube with a 4-inch drop, made right here in the good ole USofA in Peculiar, Missouri! . I'm pretty sure it is not being twisted by different length hairpins. I was real careful not to allow any pre-load at any of the three mounting points on the hairpins.

So is having that 1.5 degree differential a concern? I guess I could twist most of it out with hairpin adjustments, but that doesn't seem wise.

 

[2old2fast]

Geez ,Lee that sounds like a bunch!! No ,I doubt you could "twist" the axle w/ your radius rods , 2 plans of attack , either an alignment shop "iffy putting that much strain on the assembly" or a different axle !!! [I'd go w/ the latter....
dave

 

[Gerry]

lee
This may sound crazy but
I have looked very carefully at the front axle between the RR mounts and the king pins under braking and noticed that it flexes. That is the axle 'winds up' in reaction to the braking force. My old set up was allowing the king pins to rotate so much that I changed the design of the RR mounts.
Just wondering if after many miles the constant twist in the axle between the RR and the king pins could have 'set' and put one side out by 1.5 degrees. Probabaly talking out of my butt.
I am going to mount a vid camera and see what actually happens on this portion of the axle in the rear world.
G

 

[Lee_in_KC]

2old... LOL, I've been looking for an excuse to get a drilled I-beam axle... maybe this is it!

Gerry... I noticed the same thing. Mine actually flexes axially AND vertically... axially during hard braking, and vertically when hitting sharp bumps. And like you, I'm talking about between the kingpins and the bat wings, which on my set-up is 8 inches. Another reason I was thinking of going to an I-beam... I hear they don't flex as much.

 

[2old2fast]

Lee , I just went out & put 1 of my angle finders on top of the kingpins , mine "showed it was off by 2 * , but wait , that was my old angle finder , tried w / my new 1 & the spindles are equal ,lesson eg your angle finder, make sure it's accurate....
dave

 

[Lee_in_KC]

2old... yep, I checked that. I have both an analog and a digital angle-finder, and they agree.

 

[Gerry]

2old... LOL, I've been looking for an excuse to get a drilled I-beam axle... maybe this is it!

Gerry... I noticed the same thing. Mine actually flexes axially AND vertically... axially during hard braking, and vertically when hitting sharp bumps. And like you, I'm talking about between the kingpins and the bat wings, which on my set-up is 8 inches. Another reason I was thinking of going to an I-beam... I hear they don't flex as much.

Your choice Lee and I know you know whats what.
Thing is that the only axle Ive visibly seen flex coming across a show field is a drilled I Beam. Here we have had enough failures at the RR joint that it would nt be my first choice for a front end. JMUHP (just my useless humble opinion)

 

[Lee_in_KC]

"... the only axle I've visibly seen flex coming across a show field is a drilled I Beam." Dang it, Gerry, I don't want to hear that! Got my heart set on a chromed, drilled I-beam!!

I'm continuing to fiddle with the current set-up to what I can do. Discovered I've got a galled S/S Heim joint that I can't move!! I wish I had known about anti-seize before I assembled my all-chrome front end with stainless fasteners!! Time to break out the blue wrench!!

 

[Gerry]

Then Lee
GO FOR It and check it often. Always go for what you want not for what they say. You have enough expertize to know if something is 'stressing'
Gone now for another month or so.
keep safe n happy
G

 

[sstock]

2old... LOL, I've been looking for an excuse to get a drilled I-beam axle... maybe this is it!

Gerry... I noticed the same thing. Mine actually flexes axially AND vertically... axially during hard braking, and vertically when hitting sharp bumps. And like you, I'm talking about between the kingpins and the bat wings, which on my set-up is 8 inches. Another reason I was thinking of going to an I-beam... I hear they don't flex as much.

Lee, like you, I love the drilled I beam axle. My next T will definitely have one of these. I'm checking my caster now to see if I'm in the same boat.

 

[Keeper]

From what I understand, you can take your axle to a big rig truck shop and they can straighten your axle out if its bent/twisted.

I think I would fiddle with both sides to see if you could get it to match first.

 

[RPM]

Is the car pulling or drifting to the side with the lesser caster? A lot of factory cars have uneven caster in the front ends to compensate for the crown in the road.

 

[Lee_in_KC]

Ron, my only front end problem is shimmy. I can move it up or down the speed range with various adjustments, but I can't get rid of it!!

 

[WMG]

Lee had a similar problem of shimmy with mine. Adjusted to the point where it was the least amount then added a damper from So-Cal. can still feel it slightly at 30mph, where it was the least but does not affect handling or make me nervous. My king pins are out less than one degree and this changes slightly after a run from side to side. I think it is just a factor of the type of axle and the way it is secured. Just my 2 cents.

Wayne

 

[RESINATOR]

Lee, how (where) are you checking the angle? The top of the pin, the top of the axle, the pin itself or the wheel. We have sold a bunch of Superbell ,Magnum and TCI axles and have noticed every once in a while the bore for the pin is not centered in the boss casting/forging. Seeing first hand the fixtures for machining and welding of the axles (not lightweight amature contraptions), I cannot imagine this angle being off... but things happen.
The spindles kingpin bore are more often off-center than the axles, some less expensive brands more than others, but being off center does not mean the angle is off.
Let me know where the angle is being checked and i will throw in my two cents.
Also, almost all of the cars we've worked on that have had wobble/hop issues are solved with accurate measuring (triangulated), adjustments of the bars to eliminate preload, wheel balance and messing with the toe adjustment (this is rarely the same on any car and even changing tires will sometimes affect what works..adjust-try-repeat). This is assuming the car has shocks, I know yours does.
The steering dampner will help and is highly recommended, but will never be the fix if there are other issues.

 

[donsrods]

We ran into that with my Sons T bucket. Chromed tube axle and when we checked the caster it was different by about one degree from one side to the other. We simply adjusted the radius rods to "twist" his axle down on one side a half degree and up a half degree on the other, so they are now the same. It doesn't take much with a floor jack to push the back of the radius rod up once you adjust it to where it needs to be.

Don

 

[Lee_in_KC]

Jerry, I checked the angle by setting the angle finder on the steering arms, which are the TP flat bar front steering arms. This assumes, of course, that the steering arms are dead perpendicular to the king pins. I can see how there might be a 1.5 degree difference between the steering arms, since they are not keyed in any way to the spindles beyond the two securing bolts.

The difference in inclination/caster is not really bothering me. I was just surprised they didn't match. I am more concerned about the wobble/shimmy. I have been chasing this problem for the six years the car has been on the road. I have tried every recommendation anyone has ever made on this site as well as the NTBA and Hotrodders.com sites. All I have been able to do with adjustments is move the speed range where the wobble occurs up and down. Yesterday I tried changing the front tire pressure (again), raising it from 24# to 32#. All this did is raise the wobble range from 25-30 mph to 30-35 mph. Caster is currently 5 degrees on the left and 6.5 degrees on the right (if my method of measuring is to be believed ). Toe is about 1/8" in. Wheels/tires were spin-balanced on the car. I have hydraulic shocks and no steering dampner (I have front steer, so no place to mount a dampner). Everything in the steering train is tight. Pittman arm is properly mounted on the steering box.

I need to get this fixed before Chattanooga!!!

 

[T-Odd]

Lee, have you put another set of rims on the front? We had a death wobble on the model A pickup that was scary. Riding along on smooth roads then all of a sudden you'd have to slam on the brakes and come to a complete stop before being able to control it again.

We checked toe in /toe out / caster / camber, etc and then changed rims and tires to something else. Fixed the problem immediately. Still not sure how the tire guy double and triple checked, all balanced correctly... still makes me scratch my head.

 

[T-Odd]

This drive down to Sun, I was driving next to him and saw it happen... and his tires were flopping around like crazy.

We changed tires and rims, problem solved immediately. This is the only pic I could find right now.

 

[Cool32]

Have you tried reducing the toe in to 1/16 or less also have you tried reversing the axle???