Adjustable upper control arm opinions.
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.
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.
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.