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

[MoPar~Man]

What am I doing wrong, exactly, by first trying a max-caster setting just to see how the steering handles?

And should that max-caster setting not give the car some tendency to self-center?

I have exactly zero pieces of suspension measuring devices and given the many different gizmos out there I'm trying to figure out which direction to go.

 

[Just Carbs]

What am I doing wrong, exactly, by first trying a max-caster setting just to see how the steering handles?

And should that max-caster setting not give the car some tendency to self-center?

I have exactly zero pieces of suspension measuring devices and given the many different gizmos out there I'm trying to figure out which direction to go.

Get the caster camber gauge and try everything. Then you will know what does what.

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[MoPar~Man]

Yes I know I will get some guages.

But besides toe adjustments there's only 2 frigging upper-arm bolts and if I've got them set for max caster then having guages is not going to get me more caster, and if I'm not going to get more caster then I'm not going to get any self centering.

I haven't driven this car much in the past 2 years, maybe 10 very careful slow miles and haven't driven it at all for 20 years before that. I've forgotten how it's supposed to handle, but I know I don't like how it's driving now after a complete stub rebuild.

 

[Just Carbs]

Factory king pin inclination has a lot to do with return to center and straight-line handling.
You might like a lot of positive caster.
What is the car doing now on the interstate? What are the settings now? Your pictures indicate max caster now?

 

[Big_John]

Yes I know I will get some guages.

But besides toe adjustments there's only 2 frigging upper-arm bolts and if I've got them set for max caster then having guages is not going to get me more caster, and if I'm not going to get more caster then I'm not going to get any self centering.

I haven't driven this car much in the past 2 years, maybe 10 very careful slow miles and haven't driven it at all for 20 years before that. I've forgotten how it's supposed to handle, but I know I don't like how it's driving now after a complete stub rebuild.

Offhand, by looking at these pics, the adjustment bolts look like they are set for minimum castor. It is hard to see in the pic, so I may be wrong, but it sure looks like you've set the eccentric bolts so the front is tipped down and the rear tipped up. Both eccentrics would need to be turned 180°

 

[Just Carbs]

Offhand, by looking at these pics, the adjustment bolts look like they are set for minimum castor. It is hard to see in the pic, so I may be wrong, but it sure looks like you've set the eccentric bolts so the front is tipped down and the rear tipped up. Both eccentrics would need to be turned 180°



View attachment 687474View attachment 687475

That's what I thought. But the passenger side looks to me like the top ball joint has been moved as far back as possible?
That's max caster.

 

[Just Carbs]

From what Morar Man says, maybe his suspicions about the box may be right. I would expect the wheel to snap to the side if the valve is all the way to the limit.
Maybe the next test is to put the control arms on jack stands and start the car and see what happens.

 

[MoPar~Man]

Top is driver side, red lines through bolts.
Bottom is passenger side, yellow lines through bolts.

Standing beside each tire looking from above, both arms rotated to the max (driver side rotated CCW, passenger side CW) to move both upper ball joints rearward towards back of car.

Does this not give max positive caster?

 

[Just Carbs]

It does.
Your pull would indicate a camber bias, except it's not consistent across the steering range.
So, you might be right about the box.

 

[MoPar~Man]

Factory king pin inclination has a lot to do with return to center and straight-line handling.
You might like a lot of positive caster.
What is the car doing now on the interstate? What are the settings now? Your pictures indicate max caster now?

What is the "king pin" ? I could google it, but I can imagine the variety of results I'd get.

I'm only driving it in a short loop around the (inner city) block. Lets just say there are reasons why I don't want to drive this far from home.

I'm keeping speed down to about 25 mph (40 kph) primarily because even during low-speed stops I have to be light on the brakes because the rear wheels (don't know if it's 1 tire or both) are locking up for some reason (that kettle of fish is for a different thread if I can't solve that, which I haven't even begun to).

 

[Just Carbs]

Kingpin inclination.
The top ball joint is closer to the car than the lower ball joint. This is called the kingpin angle. This makes the spindle bearing shaft drop when the tires are turned left or right, and rise when the tires are running straight. That makes the car rise when the wheel is turned and drop when the wheel is straight. That makes the car run in a straight line and return to center coming out of parking lots.

 

[Big_John]

That's what I thought. But the passenger side looks to me like the top ball joint has been moved as far back as possible?
That's max caster.

Top is driver side, red lines through bolts.
Bottom is passenger side, yellow lines through bolts.

View attachment 687489

Standing beside each tire looking from above, both arms rotated to the max (driver side rotated CCW, passenger side CW) to move both upper ball joints rearward towards back of car.

Does this not give max positive caster?

I still think this is wrong. The rear concentric bolt needs to be at 6:00 and the front at 12:00. What I'm seeing is the opposite.

That said, until you get all the adjustments in the ball park, you aren't going to be able to tell much from driving.

 

[Just Carbs]

I still think this is wrong. The rear concentric bolt needs to be at 6:00 and the front at 12:00. What I'm seeing is the opposite.

That said, until you get all the adjustments in the ball park, you aren't going to be able to tell much from driving.

Oh. Well, I was going by the concentric washers. Thinking that would put the top ball joint behind the lower ball joint. And that would put the tire contact patch behind the ball joint vertical line. And the tire would follow the vertical line and try to go straight, if there is no wind or crown. If that's positive caster.
So, I'm confused.

 

[Big_John]

Oh. Well, I was going by the concentric washers. Thinking that would put the top ball joint behind the lower ball joint. And that would put the tire contact patch behind the ball joint vertical line. And the tire would follow the vertical line and try to go straight, if there is no wind or crown. If that's positive caster.
So, I'm confused.

I might be confused too... My thought is that you want to tip the upper control arm and that would tilt the spindle in the correct direction, but I'm also understanding what you are saying.

 

[HWYCRZR]

If the Adjustment bolt is low on the back of the control arm and high on the front of the control arm your axis between ball joints will be angled to the rear of the car giving you positive caster angle.

If the adjustment bolt (Not the eccentric washer) Is high on the back of the control arm and low on the front of the control arm you will get a more negative camber angle. (Axis angled forward).

First step of alignment, make sure your ride height is set which can be done with a tape measure. If your front height is too low, it will be difficult to get positive caster as it increases the forward angle of your angle of your control arms. Same if the rear of the car is jacked giving it a forward rake.

Again caster angle should not cause a pull in one direction or the other unless you are not even from side to side. It usually makes it wander. If you are consistently pulling in one direction, check the camber, and if that is set correctly then you need to get into setting your steering box.

But now that you have moved your alignment all around with out any gauges or measurements, you will want to re-set that to nominal. In alignment of a 50+ year old car you cannot expect that if the bolts look equal from side to side that your alignment is set evenly, there will be some differences from side to side. Then you can work on your steering.

Maybe it is the perspective of the picture you had above, but it looks like your drivers side front is higher than your passenger side?

Alignment Step 1. Air pressure equal in all tires, (and I believe they recommend at least half full of fuel)
Alignment Step 2. Adjust the ride height by adjusting the torsion bars so that you have the same measurement from side to side.
Alignment Step3. Adjust your caster angle
Alignment Step 4. Adjust your camber
Alignment Step 5. Adjust your tow in.

If you have verified that your ball joints and other suspension part are in decent shape and it is still pulling then you can get into the steering system.

Get the alignment set correctly first (with measurements) then you can rule out your alignment and focus on the next task.

 

[Big_John]

If the Adjustment bolt is low on the back of the control arm and high on the front of the control arm your axis between ball joints will be angled to the rear of the car giving you positive caster angle.

If the adjustment bolt (Not the eccentric washer) Is high on the back of the control arm and low on the front of the control arm you will get a more negative camber angle. (Axis angled forward).

This is exactly how I was thinking it should be.

 

[Retired auto tech]

Not mentioned here but are all the steering components good and within wear specs? Just thought I'd ask.

As I see it there are two things that no one has mentioned. First, as per Chrysler instructions you must always adjust vehicle height to spec before doing any other adjustments. This especially true on our old cars because the sway bars are going to be sagging just like the rear leafs or a coil spring would. The nice thing is that the sway bars can be adjusted to bring height back to spec. The FSM will show you where to measure the two points and and what to set it too.

Second is to adjust the steering box sector shaft before proceeding with the alignment. Actually this applies to all circulating ball steering boxes regardless of the make. Next check how much have the rear springs sagged and is the rear end still tracking properly? Sagged rear springs can have the rear of your car trying to go in a different direction than what you are steering the front end.

If you set the castor to 1 1/2 degrees which is agout max with the stock adjusters and it still not returning to center, you can gain a little more be replacing them with aftermarket ones that can go up to 2 1/4 degrees. Rock Auto sells them for about $ 12.00 a set. As I stated before radial tires track and roll in completely different way than bias ply. Without a little extra caster they can feel squirmy going down the road not quite following your steering wheel input. Some tires may only need 1/4 degree extra, others maybe 3/4of a degree. Driving the car to see if it feels right to you is the only way to figure this out.

As for doing your own alignment save your money. No home garage floor is going to be perfectly level and without the turntable plates your numbers are going to be a crap shoot, and you are starting out with a problem because driving onto the plates set on the floor will put your car out of level. And plates are not cheap. To get your angles you are rotating the wheels not the steering wheel.

An alignment rack has the plates recessed so they are flush with the rack. On a rack the adjustments are exact and repeatable which you are not going to get doing it yourself.

The only way to do it so that it steers properly and save your tires from premature wear is to get a four wheel alignment done from a reputable shop. It will probably cost you less than buying the tools for yourself. The new alignment machines are awsome and they can measure all of the angles in only a few minutes. Discuss with them what your concerns are and see what they suggest.

 

[MoPar~Man]

I'm gonna look at this in more detail:

I'll alter the screws from one extreme to the other, and measure how far the arm moves front-to-back from a fixed reference to the center of the upper ball joint.

Remember that the adjustment only moves the upper arms in a horizontal plane parallel to the road. The purpose seems to be mostly to adjust camber, which was very important for bias tire wear back in the day. And you can't turn the bolt through a full turn - or at least I couldn't with these bolts. Only a half-turn.

But right off the bat, there's a problem. Because of the cock-eyed angle that they mounted the arm to the frame, you'll get different dimensions at different arm-angles. Here's what the arm looks like when it's against the upper stop, and when it's at what I'm going to call a typical ride angle:

The ball joint has moved rear-ward. Regardless how the bolts are set, the arm moving from the low angle to the normal ride angle has moved the ball joint backwards by 1 to 1.25 inches. I doubt the lower ball joint has moved (other than up). When the front end is bouncing, caster is changing. A lot.

Keeping the arm at a constant angle (either low or normal) but adjusting the bolts to their maximum opposing positions (which gives the full lateral range forward or rearward for the ball joint) allows for a total range of 1.125 to 1.25 inches.

To solve for the total possible caster range, assuming the distance from upper to lower ball joint is 12 inches, consider a triangle with 2 sides of 12 inches and the third side having 1.25 inches. The narrow angle is the theoretical caster range. This works out to be 6 degrees. Where exactly the zero-degree position is, I don't know. They could have allowed for -1 to +5 degrees of caster, for example. If they were smart, they would have allowed for more positive vs negative caster.