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...

 

[twostick]

The usual procedure is to jack in as much caster as it will give you, set the camber, and hope you have some positive caster left when you're done.

If you need more caster, the offset upper control arm bushings are the solution, but IIRC you install them clocked differently, as their intended purpose was to gain camber, not caster.

Kevin

 

[3175375]

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.

I’ve also been told that you need some offset on caster to account for the crown on the roads. I think an account for road crown would be unnecessary as the crown is all over the place with the roads.

What I recall is to set caster first, but I suspect that it’s iterative…

 

[413]

Doing an alignment with eccentrics is tricky to get it right, takes multiple adjustments and measurements. Big thing is the eccentrics move the numbers a different amount if they are centered verses at the end of travel.

I don't bother with Road crown anymore, the roads are either brand new or very old, so what are you gonna do.

 

[413]

The usual procedure is to jack in as much caster as it will give you, set the camber, and hope you have some positive caster left when you're done.

If you need more caster, the offset upper control arm bushings are the solution, but IIRC you install them clocked differently, as their intended purpose was to gain camber, not caster.

Kevin

Yes this is it right here. Due to differences in the car and parts side to side will depend on how much caster you will have.

I had one car that was in an accident in the past and pulled hard. After an alignment it didn't have much cater. So I change all the control arms and spindles and it was fine after that. So bent parts was the problem. But you couldn't visually see them.

 

[CBODY67]

If you real alignment procedures from the earlier 1960s, it mentions compensating for crowned, rural roads, by changing the caster so the vehicle would "lead" to the high part of the road. End result, when the vehicle was driven on those rural roads, the steering wheel would be "straight", but when they drove on a flatter road, it took some counter-steering to drive on that flat road. So it was suggested that the aligner ask the customer where they drove most, in the country or "in town", so the caster could be set accordingly.

In some specs, there is also a "cross-car caster" setting range, to allow for this, and still be in specs.

In our modern times, ALL roads have some "slant" to them, toward the outside edge of the road. Even flat Interstates. Moisture drainage is the reason.

With our Chryslers set to factory specs at the dealership, NEVER had any issues with tire wear or straight-line handling.

Caster can also be used to "tune" steering effort. Most manual-steer cars from the 1960s had negative caster settings, factory. Power steering cars had positive caster settings. "Positive" meant up to 1* positive caster, usually. In later years, as power steering saw much higher installation rates, only the power steering spec was used.

Enjoy!
CBODY67

 

[MoPar~Man]

The story so far, here's how the upper arms look:

So upper ball joints are pushed as far rear-ward as possible, to give the most positive caster. The '67 Monaco/Polara service manual calls for 0 to -1 degrees of caster (for manual steering) and .25 to 1.25 of positive caster for power steering. I don't know what the camber is, and I haven't measured or adjusted toe.

When driving forward at 20 - 25 mph:

- if the wheel is straight ahead or in a position to the left and no hand on the wheel, the wheel doesn't move, no self-centering takes place. The car will continue to go straight or continue to turn left at the same rate.

- if the wheel is turned to any position right of center, and hands taken off the wheel, the wheel will have a tendency to turn more to the right by itself.

So there appears to still be some problem in the steering gear valve body position, even though I have moved it as far forward as possible.

But the lack of tire self-centering while moving forward is probably, maybe not related to the steering gear?

 

[HWYCRZR]

Try this page in the link to maximize caster. ‘68 Polara Alignment by the book

Pulling to one side seems like a camber issue. Like riding a motorcycle if you lean the tire to the right it will turn right. Also described around the link above.
Caster is more of a wander symptom versus a pull to one side or another.

 

[Just Carbs]

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?

Front end alignment does indeed have a big impact on the total personality and driving experience of the car. And sense you are asking questions about it, it sounds like it would be worthwhile to get educated on all aspects of the geometry. When you understand cause and effect and apply it, that's when you will really get excited about driving your car. It's all very simple stuff. VERY SIMPLE STUFF! HONEST, IT IS.

A few things to know that don't get talked about.

Positive caster.
Positive caster will make the car sensitive to road crown, wind side pressure, and will increase steering effort required to maintain a straight line AND turn into corners. Yes, positive caster will cater to the cars "inertia" tendency to stay in a straight line, but ONLY it's inertia. The key word here is CASTER. What does the word mean? In this case it means "swivel" caster. And swivel caster allows the wheels to be "compliant" to any side force that is applied to the car. That force is road crown and wind force. If you run excess positive caster the car will follow the crowns (both right and left) and be blown around by the wind and the trucks. It's like this, if you roll a chair with caster wheels across a non-level floor that slopes to the right, what happens? It goes to the right.
So, if we set up a car with the currently popular overabundance of positive caster it will be a pain to keep straight on the interstate. Cause/effect.

Negative camber.
Steering wheel return centering is provided by kingpin inclination gravity as a result of the weight of the front of the cat. Negative camber reduces kingpin self-centering effect.
So, if we set it up with the currently popular excess negative camber the kingpin inclination will not be sufficient to return to center out of low-speed turns and excess positive caster will be needed. Cause/effect.

Toe.
Absolut zero or "any" negative toe will cause the car to hunt and over correct on the interstate. Cause/effect.

Now, on the other hand, if you want to race the car on a left/right road course, you will need LOTS of positive caster, negative camber and negative toe. But then it won't do anything but jump in and out of turns.

Get one of these. It comes with instructions.

Camber, Castor, & Kingpin Inclination Wheel Alignment Gauge w/ Magnetic Adapter | eBay

Experience the pinnacle of precision with the AutoSolo Magnetic Camber, Castor & King Pin Gauge. The tool seamlessly mounts onto hubs, brake discs, and can also be paired with the AutoSolo Wheel Clamp with Magnetic Adapter.

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[USSMOPAR]

Wow...I have been doing something terribly wrong with all those cars I drove/worked on over the last 30 years - omg they were aligned with modern tires/shocks etc using the proper settings that have been posted by others ad-nauseam. Something must be wrong as none of these cars wandered or anything but drive ever so nice - not the bs of what is being posted. One of those cars was a big c body pulling a car trailer and we did not crash
ad nauseam adverb
1. used to refer to the fact that something has been done or repeated so often that it has become annoying or tiresome