Adjustable upper control arm opinions.

[72bluNblu]

The 68 Dart that belonged to a friend was here for an engine build and suspension refresh. The owner bought PST tubular UCAs. The driver side aligned fine, the right side did not. We put the stock UCA back in and it aligned fine. I can't see how to blame anything except the PST part.

Yeah that sounds exactly like the issue on your friend's car.

Obviously the OP would need to check his to see, but clearly the PST UCA could be the problem. The fact that it's the same side as the one your friend had an issue with certainly seems like a lot of coincidence.

 

[DionR]

I believe the 1.0's are still available elsewhere, just not from Peter. The bad would be that the ones Peter sold came with the Delrin and zerk fittings. I don't think ones purchased elsewhere have that.

You can buy all the parts direct from SPC if you want.

And the complete control arms are available from Summit. Sort of.

Left:

SPC Performance 94461 SPC Performance Control Arms | Summit Racing

Right:

SPC Performance 94460 SPC Performance Control Arms | Summit Racing

The "sort of" comment has two parts. First, while I can't say for certain, I think the inner metal sleeve and washers for the inner mounts are different between the above and Peter's (@BergmanAutoCraft). Based on the pictures of the above, they don't look like what I bought. Second, I think SPC discontinued the style of the UBJ mount as shown on the right (PS) arm.

The UBJ on the right arm above is tipped, but in the front/back direction in relation to the car.

The left (DS) is tipped in the in/out direction in relation to the car.

It appears SPC has discontinued the part with the UBJ angled back (gold part above) and only lists the one with the UBJ angle in/out (black part above). Not sure it really matters, but it is a difference. I talked to a guy from SPC at SEMA and while he vaguely remembers a change, he couldn't tell me why or even what for certain.

No idea if the remaining 94460 arm from Summit would have the UBJ angled front to back like it is shown in the pictures on Summit's website, but my guess is that the 94461 arm will have the new style since it will ship direct from SPC.

So, while you can buy all the parts or a complete control arm, I think the inner mounts will force some rework that Peter's did not. So yes, you can get there, but not as smoothly as buying them from BAC.

 

[tcanin00]

I believe the 1.0's are still available elsewhere, just not from Peter. The bad would be that the ones Peter sold came with the Delrin and zerk fittings. I don't think ones purchased elsewhere have that.

I could drill them for the grease zerks and make delrin bushings if necessary.

 

[tcanin00]

I’d figure out why that right side is so far out. +3° to +.5° is more than just bad production tolerances.

@Kern Dog made a point about a right side PST UCA that was jigged incorrectly, might not be coincidence that your right side is also the one that’s off



Yeah there are SPC genI’s around still, I think SPC has discontinued them so you’re looking at who still has stock on the shelf.

Believe you’re correct about the bushings and zerks too.

The Gen II’s are very nice, but they are pricey.

Yes, those were the numbers I had to work with. I didn't try to adjust the stock UCA's, so I don't know for sure if it's a problem with the car or the control arm.
I read Kern Dog's post and that's what got me thinking that the arms are not the same.

 

[tcanin00]

The 68 Dart that belonged to a friend was here for an engine build and suspension refresh. The owner bought PST tubular UCAs. The driver side aligned fine, the right side did not. We put the stock UCA back in and it aligned fine. I can't see how to blame anything except the PST part.

It was your thread that got me thinking about this. I sold my original uppers before realizing there might be a problem with the PST arms.

 

[tcanin00]

Yeah that sounds exactly like the issue on your friend's car.

Obviously the OP would need to check his to see, but clearly the PST UCA could be the problem. The fact that it's the same side as the one your friend had an issue with certainly seems like a lot of coincidence.

If I'm not mistaken, a couple of guys in Kern Dog's thread said there was a bad batch of PST arms that weren't jigged up correctly. I don't know if PST offered replacements or refunds, but that train has set sail.

 

[tcanin00]

You can buy all the parts direct from SPC if you want.

And the complete control arms are available from Summit. Sort of.

Left:

SPC Performance 94461 SPC Performance Control Arms | Summit Racing

Right:

SPC Performance 94460 SPC Performance Control Arms | Summit Racing

The "sort of" comment has two parts. First, while I can't say for certain, I think the inner metal sleeve and washers for the inner mounts are different between the above and Peter's (@BergmanAutoCraft). Based on the pictures of the above, they don't look like what I bought. Second, I think SPC discontinued the style of the UBJ mount as shown on the right (PS) arm.

The UBJ on the right arm above is tipped, but in the front/back direction in relation to the car.

View attachment 1716478538

The left (DS) is tipped in the in/out direction in relation to the car.

View attachment 1716478539

It appears SPC has discontinued the part with the UBJ angled back (gold part above) and only lists the one with the UBJ angle in/out (black part above). Not sure it really matters, but it is a difference. I talked to a guy from SPC at SEMA and while he vaguely remembers a change, he couldn't tell me why or even what for certain.

No idea if the remaining 94460 arm from Summit would have the UBJ angled front to back like it is shown in the pictures on Summit's website, but my guess is that the 94461 arm will have the new style since it will ship direct from SPC.

So, while you can buy all the parts or a complete control arm, I think the inner mounts will force some rework that Peter's did not. So yes, you can get there, but not as smoothly as buying them from BAC.

Thanks for taking the time to look into this. It would be interesting to know the reason for the change in the ball joint position.

 

[72bluNblu]

If I'm not mistaken, a couple of guys in Kern Dog's thread said there was a bad batch of PST arms that weren't jigged up correctly. I don't know if PST offered replacements or refunds, but that train has set sail.

Honestly if you know the date you purchased your PST UCA's it can't hurt to call them. I know they sold to Kanter but there should be some record of that bad batch, and if you could confirm your UCA's were part of it at least you'd know the issue.

Otherwise you might need to get ahold of a known good right UCA to compare to. If you don't and just buy new UCA's you run the risk of just throwing more parts and money at a chassis issue. Even if the UCA is the more likely culprit, it's still a risk.

Thanks for taking the time to look into this. It would be interesting to know the reason for the change in the ball joint position.

It typically improves camber gain and roll center geometry in A-body handling applications.

 

[DionR]

I think Peter Bergman looked into it and came to the conclusion that a 1/2" taller ball joint would improve the roll center further on his car which I believe also runs FMJ spindles.

I am going to be a small, unimportant, dissenting voice to this. But I don't have years of experience in either racing nor design so take it for what it's worth.

The idea behind getting the roll center up as high as possible is to reduce the roll couple (distance from roll center to GC) so there is less leverage to make the car roll in a corner. As best I can tell from what I have been able to measure, this is what an F-Body spindle and longer UBJ does. It get's the roll center higher and shortens the roll couple. The problem is, a high roll center and short roll couple increases the jacking effect which has negative results due to the car actually rising in the corner. On the other hand, a low roll center has less jacking but more leverage for the CG to make the car roll. In the end, there is no way to counteract jacking, but a longer roll couple can be tuned for with heavier springs and bigger sway bars. Certainly there is a diminishing return and springs and sway bars can make the car rough to drive on the street. But like everything else in this world, the question becomes what to compromise and I think I have settled on the opinion that a low center is better than a short roll couple.

After walking around SEMA and talking to a couple of guys, plus looking at various online aftermarket suspension designs, it appears that most of the suspension that are actually designed for handling have the slope of the UCA at a very gradual rise from the middle of the car towards the UBJ. When combined with a flat LCA, this generally makes for the lowest roll center. Kits with the UCA sloping down from the inner mount to the UBJ generally result in a roll center that is underground, which is not what you want. I'm not saying all suspensions with this downward slope are bad, the slope of the LCA has a huge impact. Only that I have started to look at the LCA and UCA and it gives me a general idea of what the design intent was. Meaning, some suspensions are intended to make room in the engine compartment or upgrade to a rack, but handling is a secondary concern. Which is fine, depending on the intended uses. But it has helped me to start filtering out the kits that don't fit what my intended use is. And it has helped me to decide that most aftermarket kits that are actually intended to make a car handle better (and aren't just saying it to sell parts) design around a low roll center. Companies like Speedtech, Detroit Speed and Speedway.

So my opinion now for a torsion bar car is, get the car low enough to put the LCA inner pivot and LBJ level with the ground and then run an A-Body spindle and a standard length UBJ. This should put the RC low, even if it isn't as low as the target I have read about. But it should be the best possible combination with stock off the shelf parts. In theory.

 

[tcanin00]

Honestly if you know the date you purchased your PST UCA's it can't hurt to call them. I know they sold to Kanter but there should be some record of that bad batch, and if you could confirm your UCA's were part of it at least you'd know the issue.

Otherwise you might need to get ahold of a known good right UCA to compare to. If you don't and just buy new UCA's you run the risk of just throwing more parts and money at a chassis issue. Even if the UCA is the more likely culprit, it's still a risk.



It typically improves camber gain and roll center geometry in A-body handling applications.

I bought them used, so I have no idea when they were made. They didn't look very old or used for very long.
Yeah, it's pretty much a guessing game without having a known good UCA.
Thanks for letting me know the reason for the UBJ location change.

 

[tcanin00]

I am going to be a small, unimportant, dissenting voice to this. But I don't have years of experience in either racing nor design so take it for what it's worth.

The idea behind getting the roll center up as high as possible is to reduce the roll couple (distance from roll center to GC) so there is less leverage to make the car roll in a corner. As best I can tell from what I have been able to measure, this is what an F-Body spindle and longer UBJ does. It get's the roll center higher and shortens the roll couple. The problem is, a high roll center and short roll couple increases the jacking effect which has negative results due to the car actually rising in the corner. On the other hand, a low roll center has less jacking but more leverage for the CG to make the car roll. In the end, there is no way to counteract jacking, but a longer roll couple can be tuned for with heavier springs and bigger sway bars. Certainly there is a diminishing return and springs and sway bars can make the car rough to drive on the street. But like everything else in this world, the question becomes what to compromise and I think I have settled on the opinion that a low center is better than a short roll couple.

After walking around SEMA and talking to a couple of guys, plus looking at various online aftermarket suspension designs, it appears that most of the suspension that are actually designed for handling have the slope of the UCA at a very gradual rise from the middle of the car towards the UBJ. When combined with a flat LCA, this generally makes for the lowest roll center. Kits with the UCA sloping down from the inner mount to the UBJ generally result in a roll center that is underground, which is not what you want. I'm not saying all suspensions with this downward slope are bad, the slope of the LCA has a huge impact. Only that I have started to look at the LCA and UCA and it gives me a general idea of what the design intent was. Meaning, some suspensions are intended to make room in the engine compartment or upgrade to a rack, but handling is a secondary concern. Which is fine, depending on the intended uses. But it has helped me to start filtering out the kits that don't fit what my intended use is. And it has helped me to decide that most aftermarket kits that are actually intended to make a car handle better (and aren't just saying it to sell parts) design around a low roll center. Companies like Speedtech, Detroit Speed and Speedway.

So my opinion now for a torsion bar car is, get the car low enough to put the LCA inner pivot and LBJ level with the ground and then run an A-Body spindle and a standard length UBJ. This should put the RC low, even if it isn't as low as the target I have read about. But it should be the best possible combination with stock off the shelf parts. In theory.

Thank you posting this, it's a lot to process and think about. What you said about trying to prevent rolling by using heavier sway and torsion bars really stood out. Theoretically it would work, but it would make the car miserable to drive on the street. To be honest, I'm considering going down in torsion bar size for that reason.
Several years ago I set up a BMW E30 3 series with fairly aggressive Koni and Eibach suspension system and big Wilwood brakes. This was about ten years ago and the details aren't as clear, but I think it might of had a stock sway bar and no rear. It might not have had either front or rear, since it was a 318 base model with rear drum brakes.
That car handled amazing when it was pushed to it's limits, but it was awful to drive on the street. The guy I sold it to only autcrosses it. He said he tried to drive it on the street, but his back told him that was a bad idea. He posted in car video from his previous autocross car, a relatively stock E30, and videos from my car. The stock car wallowed and rolled through the turns, while my car was dead flat and was noticeably faster.

 

[RBConvert]

If I'm not mistaken, a couple of guys in Kern Dog's thread said there was a bad batch of PST arms that weren't jigged up correctly. I don't know if PST offered replacements or refunds, but that train has set sail.

As part of the Magnum engine rebuild at @Kern Dog's shop, I had purchased the tubular UCA's, 1.03 T bars, adj. strut rods, and rear Bilsteins (already had front Bilsteins) from PST. I bought them in January but we didn't get to the suspension until May. As Greg posted, the drivers side alignment was fine but we could not get negative camber on the passenger side. I wound up returning the two UCA's, pretty beat up from the install, and PST (now Kanter) issued me a full refund. I was expecting some kind of restocking fee because of the time lapse and condition of the parts. Could be great customer service, or maybe there was an issue with the arms so they chalked it up to a bad batch.
Anyway, I went back to the OEM control arms with stock type UBJ. Greg has the Longacre alignment tool, and he was able to dial in .5° neg camber and 2.5 - 3° pos caster (going off of memory).

 

[72bluNblu]

I am going to be a small, unimportant, dissenting voice to this. But I don't have years of experience in either racing nor design so take it for what it's worth.

The idea behind getting the roll center up as high as possible is to reduce the roll couple (distance from roll center to GC) so there is less leverage to make the car roll in a corner. As best I can tell from what I have been able to measure, this is what an F-Body spindle and longer UBJ does. It get's the roll center higher and shortens the roll couple. The problem is, a high roll center and short roll couple increases the jacking effect which has negative results due to the car actually rising in the corner. On the other hand, a low roll center has less jacking but more leverage for the CG to make the car roll. In the end, there is no way to counteract jacking, but a longer roll couple can be tuned for with heavier springs and bigger sway bars. Certainly there is a diminishing return and springs and sway bars can make the car rough to drive on the street. But like everything else in this world, the question becomes what to compromise and I think I have settled on the opinion that a low center is better than a short roll couple.

After walking around SEMA and talking to a couple of guys, plus looking at various online aftermarket suspension designs, it appears that most of the suspension that are actually designed for handling have the slope of the UCA at a very gradual rise from the middle of the car towards the UBJ. When combined with a flat LCA, this generally makes for the lowest roll center. Kits with the UCA sloping down from the inner mount to the UBJ generally result in a roll center that is underground, which is not what you want. I'm not saying all suspensions with this downward slope are bad, the slope of the LCA has a huge impact. Only that I have started to look at the LCA and UCA and it gives me a general idea of what the design intent was. Meaning, some suspensions are intended to make room in the engine compartment or upgrade to a rack, but handling is a secondary concern. Which is fine, depending on the intended uses. But it has helped me to start filtering out the kits that don't fit what my intended use is. And it has helped me to decide that most aftermarket kits that are actually intended to make a car handle better (and aren't just saying it to sell parts) design around a low roll center. Companies like Speedtech, Detroit Speed and Speedway.

So my opinion now for a torsion bar car is, get the car low enough to put the LCA inner pivot and LBJ level with the ground and then run an A-Body spindle and a standard length UBJ. This should put the RC low, even if it isn't as low as the target I have read about. But it should be the best possible combination with stock off the shelf parts. In theory.

There can definitely be some debate about this, because there are of course different philosophies on what makes for better handling. And some of it will be driver preference and the rest of the car set up too.

I'm curious though, since you measured everything, what the difference is between the center to center on the UCA and LCA pivots vs the centers of the upper and lower ball joints with the A body or FMJ body spindles. Does a level LCA (pivot to center of ball joint) actually put the upper ball joint above the UCA pivots?

Regardless, not everyone runs the LCA parallel to the ground, because that's a pretty low ride height. I don't think Peter runs his that low. In which case, you would need the taller upper ball joint to put that angle on the UCA. It's very much set up dependent.

I bought them used, so I have no idea when they were made. They didn't look very old or used for very long.
Yeah, it's pretty much a guessing game without having a known good UCA.
Thanks for letting me know the reason for the UBJ location change.

Yeah you're probably SOL. But based on @RBConvert 's experience it might not hurt to call Kanter/PST and see what they say. Worst thing they can say is no, in which case you're no worse off than you are now anyway.

 

[RBConvert]

Thank you posting this, it's a lot to process and think about. What you said about trying to prevent rolling by using heavier sway and torsion bars really stood out. Theoretically it would work, but it would make the car miserable to drive on the street. To be honest, I'm considering going down in torsion bar size for that reason.

A bigger T bar will not give a harsher ride when combined with the right shocks. On the Dart I went up from .92s to the 1.03s, combined with Bilsteins, and the car handles the best it has in the 12+ years I've owned it. I also boxed the LCAs, added PST solid tie rod adjusters, adj strut rods, and welded in SFCs. The ride isn't harsh at all.

 

[72bluNblu]

A bigger T bar will not give a harsher ride when combined with the right shocks. On the Dart I went up from .92s to the 1.03s, combined with Bilsteins, and the car handles the best it has in the 12+ years I've owned it. I also boxed the LCAs, added PST solid tie rod adjusters, adj strut rods, and welded in SFCs. The ride isn't harsh at all.

Agree!

I’ve been running 1.12” torsion bars on my Duster for well over 40k miles on the street. With a good set of shocks it’s not a big deal, it rides similar to a modern sports car.

If anything, I’ll be going up to even larger torsion bars.

 

[Kern Dog]

My 70 Charger has 1.15” torsion bars, the car weighs 3900. It rides about like the Wife’s 2015 Challenger.
Bilstein shocks really do help.
Skinny torsion bars allow too much lift and side in the front no matter the shocks you have. The car feels like a boat on a wavy lake with small torsion bars. I had stock .88” in another Charger. A couple months back I swapped in 1.03s from PST. it has crappy KYB shocks, a piss poor shock for most cars but I had the shocks here already and this car is far from finished…
The increase in torsion bar size made the car feel stable and more easy to handle.

 

[DionR]

There can definitely be some debate about this, because there are of course different philosophies on what makes for better handling. And some of it will be driver preference and the rest of the car set up too.

Absolutely.

I'm curious though, since you measured everything, what the difference is between the center to center on the UCA and LCA pivots vs the centers of the upper and lower ball joints with the A body or FMJ body spindles. Does a level LCA (pivot to center of ball joint) actually put the upper ball joint above the UCA pivots?

A-Body:

F-Body:

Note that the inside upper pivot height is dependent on caster and such. Because it is a sloped mount, the effective height is where the UBJ is at 90 degrees to the two mounts. Here is a side view of the F-Body spindle:

So less caster would move the UBJ forward and effectively raise inner upper mount height.

Regardless, not everyone runs the LCA parallel to the ground, because that's a pretty low ride height. I don't think Peter runs his that low.

Agreed, and no one should feel like they have to have to run their car that low. Frankly, I can't say for sure that I am that low with my '74. It's more of the ideal in my mind, since it get's the RC as low as possible.

In which case, you would need the taller upper ball joint to put that angle on the UCA.

True.

To be clear though, the slope of the UCA needs to be up to the UBJ when the LCA is flat. If the LCA is not flat but instead slopes down to the LBJ, I wouldn't want the UCA sloping up to the UBJ as the RC would actually climb then.

Here are some examples.

A stock A-Body ride height has a static RC of 6.3".

With the F-Body spindle and 1" longer UBJ, the RC is over 10".

This is using the stock alignment specs, don't miss that.

So, in my inexperienced opinion, regardless of ride height, an F-Body Spindle and 1" longer UBJ would be a detriment in all cases (in theory) because the RC would be higher and jacking forces greater.

 

[DionR]

Thank you posting this, it's a lot to process and think about. What you said about trying to prevent rolling by using heavier sway and torsion bars really stood out. Theoretically it would work, but it would make the car miserable to drive on the street.

I'm not saying that in all cases it would be necessary to run such heavy torsion bars and sway bars that it would be punishing to run the car on the streets. I'm just saying it might get there in extreme cases.

The big point I was trying to make is that jacking forces due to a high roll center can't be tuned out of the chassis. There is nothing that can be tweaked to resist them. The only option is to reduce the jacking forces by lower the roll center. The problem with a low roll center is a larger roll couple, but that can be resisted with springs and sway bars. At least until the springs and sway bars get to be too stiff.

A corollary to all that is, if you can reduce your CG, you reduce the roll couple as well. That's just harder to do, at least in my mind, once you get past aluminum heads and such. But if you can, then you would need less spring and roll bar.

 

[tcanin00]

As part of the Magnum engine rebuild at @Kern Dog's shop, I had purchased the tubular UCA's, 1.03 T bars, adj. strut rods, and rear Bilsteins (already had front Bilsteins) from PST. I bought them in January but we didn't get to the suspension until May. As Greg posted, the drivers side alignment was fine but we could not get negative camber on the passenger side. I wound up returning the two UCA's, pretty beat up from the install, and PST (now Kanter) issued me a full refund. I was expecting some kind of restocking fee because of the time lapse and condition of the parts. Could be great customer service, or maybe there was an issue with the arms so they chalked it up to a bad batch.
Anyway, I went back to the OEM control arms with stock type UBJ. Greg has the Longacre alignment tool, and he was able to dial in .5° neg camber and 2.5 - 3° pos caster (going off of memory).

I'm glad they gave you a full refund on the UCA's. If I was the original purchaser I would try to return them, but I bought them used.

 

[tcanin00]

A bigger T bar will not give a harsher ride when combined with the right shocks. On the Dart I went up from .92s to the 1.03s, combined with Bilsteins, and the car handles the best it has in the 12+ years I've owned it. I also boxed the LCAs, added PST solid tie rod adjusters, adj strut rods, and welded in SFCs. The ride isn't harsh at all.

I know it was worse with the KYB shocks that were on it. It improved with some generic shocks I had in the garage. I plan on getting Bilsteins in the future, just want to get the alignment right and have the car drive somewhat decent.

 

[tcanin00]

My 70 Charger has 1.15” torsion bars, the car weighs 3900. It rides about like the Wife’s 2015 Challenger.
Bilstein shocks really do help.
Skinny torsion bars allow too much lift and side in the front no matter the shocks you have. The car feels like a boat on a wavy lake with small torsion bars. I had stock .88” in another Charger. A couple months back I swapped in 1.03s from PST. it has crappy KYB shocks, a piss poor shock for most cars but I had the shocks here already and this car is far from finished…
The increase in torsion bar size made the car feel stable and more easy to handle.

Yeah, when it had the stock torsion bars it felt like a boat. The KYBs I put on with the bigger torsion bars made it feel like a low rider with cut or torched springs.

 

[abodyjoe]

A bigger T bar will not give a harsher ride when combined with the right shocks. On the Dart I went up from .92s to the 1.03s, combined with Bilsteins, and the car handles the best it has in the 12+ years I've owned it. I also boxed the LCAs, added PST solid tie rod adjusters, adj strut rods, and welded in SFCs. The ride isn't harsh at all.

agree.

we went from a 1" bar with 130 pound rear springs with kyb shocks all around to 1.08 bars and the same rear springs but this time with bilstien shocks all around. the difference was amazing. no where near harsh.

 

[RBConvert]

agree.

we went from a 1" bar with 130 pound rear springs with kyb shocks all around to 1.08 bars and the same rear springs but this time with bilstien shocks all around. the difference was amazing. no where near harsh.

Yep. Swapping the kyb's for bilsteins makes all the difference.

 

[tcanin00]

Absolutely.



A-Body:

View attachment 1716479099

F-Body:

View attachment 1716479104

Note that the inside upper pivot height is dependent on caster and such. Because it is a sloped mount, the effective height is where the UBJ is at 90 degrees to the two mounts. Here is a side view of the F-Body spindle:

View attachment 1716479103

So less caster would move the UBJ forward and effectively raise inner upper mount height.



Agreed, and no one should feel like they have to have to run their car that low. Frankly, I can't say for sure that I am that low with my '74. It's more of the ideal in my mind, since it get's the RC as low as possible.



True.

To be clear though, the slope of the UCA needs to be up to the UBJ when the LCA is flat. If the LCA is not flat but instead slopes down to the LBJ, I wouldn't want the UCA sloping up to the UBJ as the RC would actually climb then.

Here are some examples.

A stock A-Body ride height has a static RC of 6.3".

With the F-Body spindle and 1" longer UBJ, the RC is over 10".

View attachment 1716479106

This is using the stock alignment specs, don't miss that.

So, in my inexperienced opinion, regardless of ride height, an F-Body Spindle and 1" longer UBJ would be a detriment in all cases (in theory) because the RC would be higher and jacking forces greater.

This is what I'm here for. Thank you for taking the time to measure and map out the difference between A and FMJ knuckles. I've had a suspicion that the FMJ knuckles have been part of the problem with how bad my car drives. I ran them with the stock uppers, torsion bars, lowers, strut rods, and stock K member with 215/60/15's and with decent alignment specs it was borderline dangerous feeling. It wandered around on the road following ruts and felt disconnected from steering input with a 24:1 manual steering box.
Since then, almost everything has replaced. QA1 tubular K member, boxed-in LCA's with new forged, greasable pivot pins and polyurethane bushings and new A body LBJ's, QA1 adjustable strut rods, stock power steering box with a Borgeson u-joint coupler and a Magnum power steering pump that is a slightly lower pressure than the original, PST 1.03" torsion bars, and the PST uppers with new ball joints. I also went to 245/45/17's.
All of that, and it's worse. Granted, I can't get the alignment right so that doesn't help. I will say the steering feel is better. I know a lot of the problems are with poor alignment and cheap shocks, but it drives so bad I don't like driving it. I've had enough, and spent more than enough trying to make it better, but it's not.
I made the component choices based countless threads on here about making the stock style suspension work. 72blu has been one the main contributor of information on making it work better.

 

[72bluNblu]

This is what I'm here for. Thank you for taking the time to measure and map out the difference between A and FMJ knuckles. I've had a suspicion that the FMJ knuckles have been part of the problem with how bad my car drives. I ran them with the stock uppers, torsion bars, lowers, strut rods, and stock K member with 215/60/15's and with decent alignment specs it was borderline dangerous feeling. It wandered around on the road following ruts and felt disconnected from steering input with a 24:1 manual steering box.
Since then, almost everything has replaced. QA1 tubular K member, boxed-in LCA's with new forged, greasable pivot pins and polyurethane bushings and new A body LBJ's, QA1 adjustable strut rods, stock power steering box with a Borgeson u-joint coupler and a Magnum power steering pump that is a slightly lower pressure than the original, PST 1.03" torsion bars, and the PST uppers with new ball joints. I also went to 245/45/17's.
All of that, and it's worse. Granted, I can't get the alignment right so that doesn't help. I will say the steering feel is better. I know a lot of the problems are with poor alignment and cheap shocks, but it drives so bad I don't like driving it. I've had enough, and spent more than enough trying to make it better, but it's not.
I made the component choices based countless threads on here about making the stock style suspension work. 72blu has been one the main contributor of information on making it work better.

No. You have taken the wrong idea from this. Your alignment being off is 100% your problem.

FMJ spindle geometry has been looked at before, and it improves camber gain. All suspension geometry is a trade off. Ehrenberg initially made similar statements about the FMJ spindles having negative effects, he was thoroughly debunked by Bill Reilly (Reilly Motorsports) in this article with all the geometry numbers to prove it.

Swapping A & B Body Disc-Brake Spindles - Debated Usage


It should also be noted that the spindle height is not the only difference between the A body spindles and the FMJ (and B body) spindles. This footnote has been lost out of the online article I linked above after all the magazine buy outs and website format changes, but the later spindles also have more build in SAI, and are 3 lbs lighter. The increased SAI also tends to make cars MORE stable, so, the later spindles should cause LESS wandering in a like to like comparison with the earlier ones.

And I run FMJ spindles on my Duster and my Challenger. They do not cause noticeable problems. The difference between the A and FMJ spindles is quite minor, under normal driving conditions it's not a noticeable difference. Which is not to say that some cars might be better off with A-body spindles, although the argument for FMJ/B body spindles definitely improves as you increase the width and grip from your tires.

Absolutely.



A-Body:

View attachment 1716479099

F-Body:

View attachment 1716479104

Note that the inside upper pivot height is dependent on caster and such. Because it is a sloped mount, the effective height is where the UBJ is at 90 degrees to the two mounts. Here is a side view of the F-Body spindle:

View attachment 1716479103

So less caster would move the UBJ forward and effectively raise inner upper mount height.



Agreed, and no one should feel like they have to have to run their car that low. Frankly, I can't say for sure that I am that low with my '74. It's more of the ideal in my mind, since it get's the RC as low as possible.



True.

To be clear though, the slope of the UCA needs to be up to the UBJ when the LCA is flat. If the LCA is not flat but instead slopes down to the LBJ, I wouldn't want the UCA sloping up to the UBJ as the RC would actually climb then.

Here are some examples.

A stock A-Body ride height has a static RC of 6.3".

With the F-Body spindle and 1" longer UBJ, the RC is over 10".

View attachment 1716479106

This is using the stock alignment specs, don't miss that.

So, in my inexperienced opinion, regardless of ride height, an F-Body Spindle and 1" longer UBJ would be a detriment in all cases (in theory) because the RC would be higher and jacking forces greater.

All good points, and I appreciate the time you've put into plotting all of this out.

That being said, it IS ride height and alignment settings dependent. I know Peter Bergman worked out the RC for his car, and initially found that he was getting a "below ground" roll center. It's why he briefly went to drop spindles on his car before finding the negative effects of those (mostly bump steer) were worse than the RC issue. I believe he went to the 1/2" taller ball joints after that.

The bottom line is, all suspension geometry is a trade off. Improving one thing usually happens at the detriment of another, and car set up, use, and driver preferences end up having a large impact on the "best" geometry.