[Bill Verburg]

Originally Posted by phunt

.....
I feel that the position of the ball joint reference to the horizontal plane of the t-bar has to be lower or the control arm drooping or angling down.

yes but he only way to change ball joint height is by changing axle height, a
2 ways to do that
1) change tire standing loaded radius
2) raise the spindle
here's an example of (1)
when I bought my C3 new 50yrs ago, it came w/ 205/50 x 15 tires on 7" Fuchs, for the P7s that the car came w/ a is ~281 so as delivered at the dealer a - b =108, b was 173. All the other new 911's had the same a - b spec of 108 but because the had 185/70 x15 w/ a = 320 , their b spec was 212mm. They all have the same steering and bump and RC geometry, as defined by a -b. That's what a -b does. But mine chassis height was 40mm lower w/ no other effects just because of the tires. It's obvious that a shorter tire lowers the chassis, but it's not immediately obvious what a -b is measuring, as it turns out after over 50 years of thinking about this on and off(mostly off) I cam to the conclusion of what the engineers were actually describing w/ a - b, they weren't in love w/ math(well maybe they were but that doesn't matter) they weren't trying to be obtuse(probably), it is simply a description of the geometry w/ max bump travel and min roll steer at what ever ride height b is used.

Originally Posted by phunt

That is what the “c” measurement is ensuring. I believe it references the ball joint and the pivot point not the axle/spindle and the pivot point.

by definition c = a - b, the ball joint height is nowhere in there, except that for a given a the corresponding spindle position determines where the ball joint height is. if the spindle is raised from it's stock position that is the only way to move the ball joint down w/o changing b

Originally Posted by phunt

Because of the negative camber added as the ball sweeps up along the pivot arch moving the bottom of the strut out. You can also say it moves the top of the strut “in” that is what adds the negative camber.

as the suspension compresses from stock static height the camber does go a bit more neg, but not by a lot and yes it does start to go the other way eventually. See the above camber curves, if the ball joint is lower than the t-bar yeas, this caused track width to increase, I have the curves for that as well, but if the a-arm is horizontal at static ride height then the track with is strictly decreasing w/ bump.

Originally Posted by phunt

Lower beyond that point you can keep the tires contact patch square with stiff springs and ad a stiff roll bar. To me that’s a negative effect on the ride quality. I am a soft spring big bar guy.

assuming that the static geometry is in a favorable place, then yes, the faster you go, the more force goes through the suspension and the more static camber you will want and the more you want to control geometry changes due to bump/droop w/ stiffer springs, But when the suspension is made stiffer you also lose mechanical grip. So I agree, you only stiffen it the min. that keeps the car in a comfortable place to drive it. It's another of those many compromises you implement to make your usage a better experience. The factory made their compromises to suit a broad audience of end users, An owner only has to please one person(ok, sometimes 2)