Wheel alignment confusion

[Sammy]

Hi there,

after another long pause with health and family trouble I'm back on the road
with my CdV.

Had some work on front suspension and so needed realignment of the wheels.

While camber and toe in is nearly perfect the mechanics in shop can't get the caster right.

(My old shop which was pretty good with those things closed last year.

No matter how they turn the nut on the tie strut nothing happens.

They did this with brake pedal engaged (fixed with a strut to hold it down pushed)and parking brake on.

But I wonder maybe the caster is not adjustable with brake pedal engaged?
Am I getting it wrong or did they make a mistake?

I told them all instructions from the shop manual and followed the procedure
but the shop manual says nothing about engaging brake pedal.

Thanks a lot,

Sammy

[Russ Austin]

Not sure why they have the brake pedal pressed.  I would check on the condition of the upper control arm bushings.  

[Sammy]

Condition is fine, I check this everytime I went for alignment in a shop.

So I wonder: Did they make a mistake with the brake enganged and trying to adjust the caster while still sitting full weight on its wheels? 
To me it makes no sense to keep the pedal pressed

[Jason Edge]

Even if holding the brake and locking the wheel from turning could hold the force of that large strut rod and lock nuts from moving the wheel forward or back as soon as you let off the brake the tire would move forward or back. Keep in mind the tire is already "locked" just by sitting on the ground and it is not like the tire starts spinning when you start adjusting caster in either direction.  If in doubt just have them to release the brake and take a measurement. 

The only other two things I would think of that would prevent movement of the wheel when you adjust both nuts in or out, would be if your tie strut bushings at the front are busted out (which I have seen on a parts car), or the two bolts that secure the back end of the tie strut bar to the lower control arm are loose or missing.  This would be obvious to a novice mechanic much less a tire & front end shop.

For another perspective here is another picture of the tie strut which adjusts caster:

[Jason Edge]

Sammy, As noted in my messages to you, there are 2 top lock nuts to adjust Caster. One behind and one in front of the frame where the tie strut goes through. See picture below. If you just loosen the rear, rearward or the front forward nothing is  probably going to happen. If you move both nuts in or out in unison that tire is going to move... it has no choice.

[Sammy]

Thanks. As I wrote you, I got the manual and followed every step two times. 

[Sammy]

Got it. 
It was a simple, but strange problem.
Looks like the new alignment platform computer systems shops are using today here in Germany can not 
measure in time when caster is adjusted not on top but  on the lower arm as on our cars.

Once the measurement procedure is resetted and started again it is possible to do the alignment. 
But while adjusting caster you can not see it on the monitor live, have to start the computer procedure 
over and over again. Strange, but with this method it worked.

What I could not achieve was +2°.
When lock nuts on the tie-strut are set to max (where the threads end on tie-struts) it was only 
possible to achieve 0°.
Test drive was ok, so it's fine for me.

[Jason Edge]

So, I am assuming with the ability to "trick the modern machine" to measure Caster you did not have to adjust the caster to the end of the thread, and is somewhere in between either end. I remember looking at mine after you contacting me and remember 3/4" to 1" thread at the end.

Either way, it is great you got it right!

[Sammy]

Hi Jason, 

mine is at the end to achieve 0° - not possible to get it to 2°.
Don't know why.