How to adjust caster (if indeed you can with stock parts?)

[MoPar~Man]

Unless I'm not understanding this correctly, I don't see how you can adjust castor (on C-bodies? or any 60's - 70's mopar? Or in my case a slab). Looking at the wheels from the side of the car, you can't move the upper ball joint towards the front or rear of the car, and likewise for the lower ball joint. Actually, it might be possible to move the lower ball joint with an adustable strut rod? Is this ever done? Is the lower control arm bushing happy with doing that?

Does going to a radial tire make it desirable to change the castor for (I guess) better wheel self-centering?

 

[413]

The eccentrics on the upper control arms adjust castor and camber. Do you have a factory service manual, they describable it in there.

 

[MoPar~Man]

How can you adjust the castor without changing the camber? And how to you know where the 0 (zero) castor is?

 

[volksworld]

rotating the eccentrics so that the front of the upper arm is out and the rear of the arm is in towards the frame will move the upper ball joint towards the rear to maximize caster...and yes their positions also affect your camber settings but normally there is enough adjustment to wind up where you need to be....you really cant figure out actual caster degrees without a caster/camber gauge as you need to turn the wheels a certain number of degrees in each direction to measure it, preferably on turntables...i guess if you were trying to do it without proper stuff, just protractors and levels, 0 caster would be the point where you could turn the wheels without any change in camber at all

 

[CBODY67]

If the two upper control arm's eccentrics move the upper location points in together, equally, that is camber.
If the two upper control arm's eccentrics move the upper location points in equally, that is caster. Positive moves the upper ball joint to the rear, negative moves it to the front, zero is in the middle.
Adjust camber first, THEN head toward the caster adjustment.
With the tires sitting on a "tire plate", rotate the steering wheel to get a tire turning of about 20 degrees or so from forward, then turn the steering wheel an equal amount in the other direction. Noting the change of the level of the bubble level from positive to negative at the ends of that turning movement. The difference is caster.

Once camber is adjusted, the caster adjustments can be tweaked to get it close, if not exact, to the specs. A trial and error method.

IF there is no issue with steering self-centering with bias-ply tires, no issues with radial tires in that area.

To me, the reasons that people perceive they need a "high caster" front end is that the geometry of their front suspensions allows the outside wheel to lean with the car in a turn. Which means they need stiff sway bars to keep them flat.

On a Chrysler front end, the geometry lets the outside wheel go into negative camber so when the car might lean, the outer wheel remains perpendicular to the road surface. This is evident when you turn the wheels all the way one way and the outer wheel for the turn direction goes into visible negative camber as the inside wheel goes into positive camber. Which is as Chrysler designed it, from the middle 1950s! The Chrysler MasterTech course on front suspensions and alignments explains this in word and graphics, quite well. www.mymopar.com to find it!

Enjoy!
CBODY67

 

[CBODY67]

At to measuring devices, the local dealer had an adjustable bubble level that attached to the spindle. Had to remove the grease cap so it could clamp on. Which aggravated the car having Magnum500 wheels on it!

With the wheels on the wheel plates (allowing the wheels to turn side to side without friction), the wheel plates had the gauge for the number of degrees the wheel was turned, each direction. 20 degrees from center, as I recall.

Modern electronic units attach to the outer edge of the wheel rim, in about three places.

Go to Home Depot or Lowes and look for a magnetic base protractor, with a free-floating needle. Calibrated in single degrees. Placing that protractor on the raised area of the center of the wheel (where the hub cap would snap on) can probably work for the camber adj. Can also be used for the caster adj, too, just that this will work when turning the wheel one direction rather than both ways. Usually, though, one direction can be enough, I suspect. Just a suspicion!

Have the car on a surface that is level in all directions from the chassis. This is very important as to the bubble level angles.

To set toe-in, two methods. One is to set a line parallel to the rocker panels on each side. Laser levels can work for this.

With the dead spline in the steering gear input shaft at Noon (I suspect), the steering wheel shaft dead spline at Noon (for sure), the pitman arm installed so it is parallel to the rocker panels, and the adj sleeves for the tie ends installed appropriately (another "tweak" area), install the outer tie rod ends into the outer end of the sleeves and twist until everything is equal as to thread engagement. Hopefully, that should be near the desired level of "0" toe-in?

Once all of this has been set-up, adjust the toe-in to the minimum spec, if possible, side to side. Do NOT try to adjust the toe-in on one side only as then the steering wheel position will not be in the center when driving down the road. Everything even and equal, side to side, in the toe-in adjustments! Car goes straight, steering wheel looking like it should be turning.

Enjoy!
CBODY67

 

[MoPar~Man]

So basically what I'm going to do is to max out the caster (or castor, how-ever it's spelled). Pull the leading side of the upper arm out, push the trailing side in, as far as they will go. Then lock it down.

Then, to adjust camber, shim the lower 2 bolts of the spindle with washers to push it out to get what-ever negative camber I need.

 

[413]

People want most caster. So they adjust front out and rear in. But that is just a place to start, and a wishful dream. They are never adjusted like that after a proper alignment. One thing nobody mentions is that caster on each side needs to be the same or it will pull to one side.

Upper arm bushings that are offset is a safe and easy way to get more caster if needed.

I have never needed to use these offset bushings or shim the ball joints to get enough caster to have the car drive very nice.

 

[CBODY67]

From what I have seen in the replacement parts lists, the upper control arm bushings are, for the most part, offset. In the Chevy world, this is to compensate for "crossmember sag".

 

[Knebel]

Turn the wheel 20° left, note the camber. Turn the wheel 20° right, note the camber. Split the difference and thats your castor I believe. Been a while since I had done it. Its A LOT of back and forth and measuring...

Edit: Caster (deg) = (180 / 3.1415) * [(camber1 - camber2) / (turnangle1 - turnangle2)].

 

[volksworld]

So basically what I'm going to do is to max out the caster (or castor, how-ever it's spelled). Pull the leading side of the upper arm out, push the trailing side in, as far as they will go. Then lock it down.

Then, to adjust camber, shim the lower 2 bolts of the spindle with washers to push it out to get what-ever negative camber I need.

for a normal street application you probably won't need to do anything this drastic...but, yes, on our oval track cars we put washers between the ball joint and spindle to get our RF camber where it needed to be, as well as shortening the strut rod for more caster...and castor is a bean...