BrianFaulkner

I have a 2003 S6 and installed the Moog/SPC adjustable upper control arms. My local shops are saying that they cannot adjust the caster as they have no specs on it. I've even talked to Hunter and their machine has some capability to account for aftermarket parts but mine is not showing up. How have others dealt with this? What specs did you use? Moog told me 2.7 to 4 degrees of positive caster but that seems to be worthless information without the alignment machine being programmed to accommodate adjustable arms. It's headed to the stealership Monday if I can't find anything else out.
Thank you in advance, Brian.

twentysevenlitres

I would have thought you bought adjustable arms for camber adjustment, not castor??

I would have thought caster could only be adjusted by the subframe bushes which should be eccentric...

SloopJohnB@mac.com

That doesn't mean it cannot be done, but I suspect it requires adjustable lower control arms as well. Camber is adjusted by shortening BOTH UCAs; you could adjust caster somewhat by shortening or lengthening separately one or the other or both UCAs which would move the upright forward or back but would also alter the camber if not the S constant (the toe curve)…it all comes together.
Also, changing the caster that way without also changing the lower control arm geometry moves the wheel backward (increased caster) in the wheel well. I do not know if it moves it enough to be noticeable.

Neuspeed makes adjustable REAR lower control arms. If you look at the design/geometry of the front lower control arms you can see how length adjustment is not easy…the front coilover is driven by one of the lower control arms and an adjustable design would probably require adjustment before and after the coilover attachment to maintain effective spring rate. I know of no adjustable lower control arm manufacturer for street use.

BrianFaulkner

You'd be correct, the camber was way off, but as part of replacing the arms caster is affected and needs to be reset. By adjusting one arm in and the other out you can move the wheel forward and back which changes caster. I compared the center to center of the passenger and driver side last night and they are about 3/4" different because when the alignment was done they didn't pay attention to caster first, then camber and finish with toe.

twentysevenlitres

You need to find someone who knows this suspension set up for alignment.
The virtual axis created by the four pivot points has a complicated enough geometry before being adjusted!
Any adjustments will move the virtual pivot point.
I also see issues with each adjustment affecting the other - every time you change castor, you alter toe and castor, so then you fix toe and castor and knock your camber back out!
I wouldn't play with it unless I was tracking the car.

You should be able to get to factory castor and camber specs by altering the subframe.

BrianFaulkner

Took car to dealership today, $222 later it tracks well but door squeaks now, engine light came on, steering feels like an 87 Buick and speedometer stopped working within 10 miles of dealership. What the heck could they have done to make the steering feel feather light?
GRRRRRR!!!!!!