Front end alignment....Mapping the way the numbers move during suspension travel
In the March 2005 issue of Mopar Muscle magazine, Bill Reilly from RMS suspension components wrote an article covering the controversy regarding the use of the 73-76 A body disc brake steering knuckle/spindle and the other more common version used on almost everything else. F body, M,J, R and even B bodies from 1973-89 used the lighter and 3/8" taller knuckle/spindle. In the article, Bill simplifies this by comparing the A and the B spindle.
There have been rumors about how the taller unit could result in "over-angling" of the upper ball joint at full suspension compression. Rick Ehrenberg, the tech Guru at Mopar Action magazine has forever been a critic of using the taller spindle. Bill disproved that but went further.
Here are the numbers.
Note that the 0.00 in the center of the range displays the car at it's stock ride height.
If that is hard to read, here is the A body spindle numbers:
Dive indicates suspension compressing. Bill tested the spindles from ride height to 2 1/4" compressed and from ride height to 2 1/4" of rise.
Note that with the A spindle at ride height, he achieved zero camber, 1.17 degrees of positive caster and .059 of toe IN.
Go ahead and look at those numbers. What surprised me was how as the suspension rises, the caster goes away FAST. At about 5/8" of rise, the caster is effectively at ZERO.
For the people that echo the old advice to always have your car aligned after any change in ride height, look at the difference in toe from ride height to 1 1/2" lower.
It changes .016. Yeah.....sixteen thousands. Not enough to matter.
It seems to matter more if you raise the car though. Going 1 1/2" taller than stock puts you at negative caster and the toe goes from .059 in to .096. It is strange how the change in numbers is not linear.
In the March 2005 issue of Mopar Muscle magazine, Bill Reilly from RMS suspension components wrote an article covering the controversy regarding the use of the 73-76 A body disc brake steering knuckle/spindle and the other more common version used on almost everything else. F body, M,J, R and even B bodies from 1973-89 used the lighter and 3/8" taller knuckle/spindle. In the article, Bill simplifies this by comparing the A and the B spindle.
There have been rumors about how the taller unit could result in "over-angling" of the upper ball joint at full suspension compression. Rick Ehrenberg, the tech Guru at Mopar Action magazine has forever been a critic of using the taller spindle. Bill disproved that but went further.
Here are the numbers.
Note that the 0.00 in the center of the range displays the car at it's stock ride height.
If that is hard to read, here is the A body spindle numbers:
Dive indicates suspension compressing. Bill tested the spindles from ride height to 2 1/4" compressed and from ride height to 2 1/4" of rise.
Note that with the A spindle at ride height, he achieved zero camber, 1.17 degrees of positive caster and .059 of toe IN.
Go ahead and look at those numbers. What surprised me was how as the suspension rises, the caster goes away FAST. At about 5/8" of rise, the caster is effectively at ZERO.
For the people that echo the old advice to always have your car aligned after any change in ride height, look at the difference in toe from ride height to 1 1/2" lower.
It changes .016. Yeah.....sixteen thousands. Not enough to matter.
It seems to matter more if you raise the car though. Going 1 1/2" taller than stock puts you at negative caster and the toe goes from .059 in to .096. It is strange how the change in numbers is not linear.
