Caster Question?

I need advice on what to do next. First off here's where I'm at, 1974 CJ 6. I just replaced the upper and lower ball joints, new wheel bearings on both sides, all tie rod ends and a new drag link along with a remanufactured manual steering box with a Borgenson u-joint steering shaft. New BDS springs with 2 and 1/2" lift as well.

My problem is it wants to jump around on me when on the less than perfect country roads around here. Everything is tight but it just sort of has a mind of it's own on were it wants to go.

I just got it aligned and my numbers show 2.04 and 2.13 degrees. I'm not sure how to interprete the numbers and what to do next. Spring shims? If so what degree?

I've uploaded my alignment print out. Also, it appears my bottom ball joint is out ahead of my top ball joint. Is that normal? It's a factory spring under axle setup.

 

What about the toe-in? That's the red measurement. There should be some toe-in. I'd puit the toe to the middle of the range.

Pretty sure these numbers are in the TSM. As I recall, 2 degrees caster is within the factory spec, but typically you run like 4-6 degrees with lift springs.

A solid rear axle doesn't have a camber or toe-in adjustment, so that goves you an idea of the precision of the measurement. Possibly that's how it can say the toe is ok and still come up red - rounded off it's zero but the measurement is actually slightly negative.

 

I don't have the answers, just the questions--others will chime in. Does "jump around" mean "wander left to/or right erratically/unpredictably" and is "a mind of its own" emphasizing the same problem?

It will be helpful to know what tires you are running---bias or radial, size, type, etc.

I run slight front toe-in even with radials.

 

"Jump around?" Like Death-Wobble, an uncontrollable shaking?

No point to considering anything else until you get some toe-in on it. That will bias the tires to self-center. Without it, they may be hunting left and right, and getting into a self-reinforcing harmonic. =Death-wobble.

Tire balance can be a big factor too. Shocks also.

 

I have 31 inch radial tires on it that were recently balanced and rotated.

Tim, I'm not sure why they set the toe there. I would if I should take it back and say readjust to a 1/8th toe in?

No death wobble, more like dart off to one direction or the other. It also doesn't return to center after a turn like it use to before I replaced everything.

If I were to order shims would I want 4 degree shims to get a 6 degree caster? I'm confused if the 2 degrees I have now are negative?

 

Toe in.
Take it back, make 'em do it right.

 

Yep, I would take it back and ask them to put the toe in the middle of the range. Easy.

Re the caster, you probably had more caster before you installed the BDS springs. This matches my experience with the BDS springs. Yes, you have 2 degrees now - if you add a 4 degree shim you should have about 6 degrees positive. My local tire store offered to measure the caster again after adding some of Mike's shims - I have not taken them up on the offer ... yet.

 

I'll take it back.

Ok, just to make sure I've got this. It appears to me that the bottom ball joint is closer to the front of the jeep than the top ball joint. Which is what I suppose is the 2° measturement. It appears to me that if I add the 4° shim with the thick part of the shim wedge towards the back of the jeep, I will bring the upper ball joint back and the lower ball joint forward. So my thinking is, I will be back to 2° but in the opposite direction.

What is positive and what is negative? I want my top ball joint ahead of my lower right? 6° ahead to be precise for a 6° positive caster?

Sorry if I'm repeating the same question but I'm having trouble understanding this.

 

you want the thicker part of the shim facing forward for positive caster.

 

Thank you guys...I got it now. For some reason I thought I needed the top ball joint out ahead of the lower. ( I was literally thinking of a shopping cart caster but I wasn't computing the lines like in the above diagram.)

I'll order a 4° shim wedge and apply it with the think part facing the front of the jeep.

Any opinions on the best/safest wedge to get?

 

Extreme positive caster -

 

I am playing with this right now on my 71'. I replaced the D27 with a narrow track D30. Mine was doing the exact same thing. The toe was way too much and is now about 1/8". It helped but my caster is between 0 & 1 degrees. From what I have been told you want between 3-5 degrees positive. I am looking at a 4 degree shim, made of steel (forget aluminum) from Rubicon Express.

 

get the shims from mcruff on this forum.

 

Is Mike and Mcruff the same person?

 

Yes. My shims are installed, I just have not been back to the tire store.

Mike's work is exemplary.

 

Yeah, but is it any good?