Settin up caster for SAS's...

[zachis4wheeling]

I have a question about setting up the caster when ya do an SAS. I got a Dana 60 kingpin from an 87 F350 I'm planning on putting under my Ranger. I am not planning on using Ford Radius arms or anything with c-wedges at this time so setting up the caster will be a little more difficult than figuring out the lifted coil height, radius arm mounting drop bracket and going from there by using c-wedge bushings. It's not impossible by any means. People set up suspensions everyday; I know that, but this is just different than the usual fix by using c-wedges on a lot of trucks. I think that this could be useful to anyone wondering about caster setup.....not just myself.

When you go to do the final welds on everything, how to you figure out the correct caster for the front axle for it's ride height for the steering knuckles. You know what I mean? So when you turn the tires, it just turns them on an even plane; so it doesn't jack the truck up a little and flop it up and down as if your knuckle angles were off. You see on show trucks sometimes (the ones that keep their front driveshafts), a lot of the extremely tall ones have to cut and rotate their pigs to point up at the tcase cuz' the driveshaft angle gets fawked up. I don't plan on going so high I have to do that but when I put the 60 in there, I'd like for the steering knuckles to be balls on....know what I mean?

Here's the impression I was under on how to do this......assuming that the front flat surface of yur diff is prefectly vertical when yur at ride height....couldn't you just keep that level when designing your suspension as long as the knuckles were also perfectly vertical as well?

That brings me to another point. If you wanted to, couldn't you build a jig to hold yur axle so that the knuckles were perfectly level throughout the suspension design? Assuming that the knuckles on the axle were perfectly level when the pig was at a perfect 90 degree angle to the floor, would this make sense? Basically what I am thinking, is this. If I had the axle sitting there on a set of low jackstands or something, and I used a 2' carpenters square and got the axle so that the face of the pig (the flat surface where ya mount the diff cover) was vertical, and squared it off of the floor perfectly; would this work to set the knuckles? If you welded a jig up as long as you held it with the pigs face against one side of the 2' carpenters square and the other side against the floor while welding it?

If this method could work for the axle I have, sweet! But like anything, I don't think it's that easy at all, but I could be right. IF i am wrong, (which I probably am)....could someone point me in the right direction here?

I understand how if for example you have a 4 link with a adjustable upper(s) or lower(s)....you can make small changes that way, but I guess what I mean is where do I measure it from? How do you measure the caster so when I build links, they'll end up somewhere in the middle....not maxed out one way or another and still have room for adjustment....know what I mean?

I did a search for caster and all I found were a couple posts about the specs and tolerances that caster should be within for certain axles....

If anyone has any idea wtf I'm talkin about, post up! I'm all ears on this one.

Zach

 

[JohnnyU]

They way I'm doing it is pretty simple. The axle sits on jackstands at near static ride height, using an angle finder you can set the caster of the axle. The truck/chassis should be at near ride height just for simplification. From that point, you can take more accurate measurements if you need to for recalculation, or validation and initial fabrication/tacking things in place.

The biggest undetermined variable for me is coil bucket location on the frame. I have a set of coils that I'd like to try to use, but I'm not sure if they're work to my satisfaction. That said, they are easily changed if I find something that will work better. I'm also using and adjustable coil bucket, so that will give me some more room for error. I'm hoping to get further along with it this week....

 

[rickcdewitt]

it sounds like you want your ball joints straight up and down,that would be 0 caster and a bad idea.the truck is supposed to jack up and down from side to side when you turn, it helps the steering wheel return to center and keep you driving straight.the upper ball joint should be leaned back in relation to the lower.

you are on the right track though,keep the pinion and yoke at the same relative angle as the donor truck and caster will be close.just don't rotate the pinion up for driveshaft angle without cutting off the knuckles and welding them back on with more caster.

not enough caster and you can get the death wobble which ain't cool

 

[TireIron]

yes, picture a line running through the upper and lower kingpin, you want the this line to be tilted to the rear of the truck how ever many degrees of caster you want to use, be it 4 or 6 or 7 or whatever you choose to use. You can set this up with the axle on stands and twist it so that the caster is where you want it and then make your brackets and measurements off of it there.

 

[Maverick]

They way I'm doing it is pretty simple. The axle sits on jackstands at near static ride height, using an angle finder you can set the caster of the axle. The truck/chassis should be at near ride height just for simplification. From that point, you can take more accurate measurements if you need to for recalculation, or validation and initial fabrication/tacking things in place.

This is exactly what I did. Set the truck as close I as I could get to static ride height. Had the axle set underneath on jackstands with an angle finder placed on the top flat part of the inner-C. Rotated the axle backwards till I reached 7 degrees, double checked all my measurements and buzzed the wedges in place.

 

[zachis4wheeling]

Everything and I mean everything else you guys said I completely understand....it's very easy to read and understand and in plain english and that's awesome.....thanks......everything from setting the vehicle at desired ride height and knowing ahead of time your static ride height of the axle....even down to the adjustable coil bucket height thing....everything I gotta pretty good grasp on.....

But this is the only part I am having trouble with......

using an angle finder you can set the caster of the axle.

What I get from this is that you want to start out with the axle setting on jackstands at the height it would be at with it mounted on the tires (and possibly even close to where it would be at with taking tire squish into consideration).....with that being said.....

you then check the axle with an angle finder.....like this....

The part I am confused with is where to do the measuring from. If I put a straightedge across the pig's cover mounting surface and put the anglefinder against the straightedge, would this work? Or do you do it out at the knuckle on the spindle studs like this picture from the tech library?

The method shown in the above pic seems like it could work, so long as the studs you set the piece of flat stock on were EXACTALY at a 90 degree angle as opposed to the steering axis, (a.k.a. the centerlines of the balljoints on the axle.....).....but is this the correct method for doing this with the axle I have is the question?

It describes caster as the following...which is kind of common sense...

"Caster is the fore or aft slope of the steering axis. The steering axis is a line drawn through the upper and lower ball joints of the knuckle. Positive caster is when the bottom of the steering axis line is in front of the tire's contact patch. Zero caster is when the steering axis is at 0o. Positive (shown) caster ensures good stability, helps maintain straight-ahead direction and promotes steering wheel self-centering. Too much positive caster causes hard steering, excessive road shock and shimmy."

And here is the pic to assist with figuring out wtf that means....

Also, it says in this writeup above..
"Positive (shown) caster ensures good stability, helps maintain straight-ahead direction and promotes steering wheel self-centering. Too much positive caster causes hard steering, excessive road shock and shimmy."

So am I to assume that you get the knuckles vertical, then kick the top backwards a little bit to within factory spec, and the bottom forwards a couple of degrees so that the steering wheel will self center? If thats the case, this seems like something that is very intricate and easy to fawk up if you don't know WTF you're doing.....Even if you do cut and rotate yur pig towards the tcase cuz yur u-joint may be binding, you still gotta account for yur caster, cuz if yur caster is good and yur u-joint angle is off, it could vibrate like a sumbitch, but if the u joint angle is good and the caster angle is off, it could be harder to steer, it could wander, or worse things. This seems like something that could very well be overlooked.

I think I got the jist of this, but I think I just need some clarification.....and maybe some #'s to be shooting for......

And like I said, could this measuring be done at the pig like I described above with a straghtedge against the diff cover mounting surface? Or is it to be done at the spindle studs on the knuckles? Or on top of the inner C as someone said? Where do most people do their caster measuring from? Does anyone know the specifics on this for a Dana 60 from an 87 F350? Or are all Dana axles the same? (doubtful....)

Any and all help is appreciated.......

Zach

 

[rickcdewitt]

you could measure off the front cover mount while the axle is under an f 350 then put your axle at the same angle.it would put caster in range but you still might need to cut and rotate for driveshaft angle

 

[JohnnyU]

D60 Kingpin knuckles (disregard the arrow):

I would use the mating surface of the kingpin cap, or the steering arm as your "datum". It is angled inward (See below), but should not affect your measurement

Your differential cover sealing face is really irrelevant in this. The caster angle is much more important than your u-joint angle. In all reality, it's not likely that your ujoint angle would be off by much, your caster is the main culprit behind death wobble. (with the exception of worn out kingpins or bushings)

 

[rickcdewitt]

Your differential cover sealing face is really irrelevant in this.

yeah i only suggested it because he sounded worried about where to measure,i'de rather directly measure it like you said

 

[Maverick]

The only pic of mine I have handy. The angle finder is just behind the balljoint on the inner-c. Obviously it's not at static ride height in this photo, just for reference.

 

[zachis4wheeling]

JohnnyU, the pics didn't work for me.....got a link to em'? And I understand what you're sayin about caster angle being more of an issue than the pinion or u-joint angle....It would just be nice if when I set up the suspension, my u joint angle comes out at a decent angle when I get my caster angle balls on....and thanks for clearin up the diff cover mating surface thing....I knew it was probably too good to be true to be able to check pinion angle there...(so long as yur balljoints or kingpins were good and tight and not sloppy)...

And by the way, that pic makes this a lot easier to understand.....

Anyone know off the top of their head if this method shown in the picture works for a Dana 60 as well?

 

[bobbywalter]

on the top of your knuckle 7-10 degrees.


if you use the cover face maybe 7-9....you have to check that verse the knuckle. most axles are different 2-4 degrees knuckle to knuckle so i split it.


and it depends on steering setup too. with no boost i would run 6-7 and shim later. with boost or full hydro 10-12.


i run 10 on the street and like it, but i have all factory steering too.