Bob Rouleau

By now we all know that there are a number of ways to increase the negative camber on the front of our cars. On mine, I ovalized the holes at the top of the shock mounts a little more to get neg 2.5. On my wife's car, Racerron installed the shims in the lower A arm. On that car he needed the whole set, or about 13 mm worth to get neg 2.5; This had a side effect, caster went to 8.8 degrees and the tires (OEM as well as P0 Corsa) rub when the steering is near full lock.

Yesterday the car went back to Ron. He called to say that notwithstanding the diagrams posted on this board showing a caster adjuster with 3 positions (holes), the car had only 2 holes and it was already in the one for minimum caster. To bring the caster back to spec he had to remove shims and ovalize the holes. He further reported that he had done another GT3 and had the same problem, the caster adjuster has two holes only.

Macfly's car also ended up with a lot more caster than spec (9 degrees I think) yet his doesn't rub. Go figure. Forkift needed only 7 mm of shims to get neg 2.5. It appears that there is a considerable variation from one car to another. In any case beware if you use the shims especially if you need to use a lot of them.

Regards,

Z06

Is the whole closest to the back of the car used for maximum caster?

How do you change it from one whole to the other?

Bob Rouleau

Z06 - I don't know. Racerron (he's on this board) did the job for me. Perhaps he'll chime in. He told me that the caster adjuster was in the hole for minimum caster as it was and that like the other GT3 he had done recently, there were only two adjustment holes and not three as shown in the tech manual. Ron is a guru on suspemnsion set up and will no doubt provide more info. I am annoyed at having paid a ton a money for those laser cut and anodized shims though ....!Motorsports offer a proper caster adjuster link with continuous adjustment for US 1,500 a side. I don't think I need to go that far for DE

64lusso

Hmmm, my car rubs a little at full lock right from the factory, wonder what that means?
Jay

Racerron

As Bob has reported on the 3 GT3's that I have aligned there are only 2 adjustment holes in the lower control arm (the same as the Mk1) although the Mk2 workshop manual shows 3.

For minimum caster the bolt needs to be located in the forward hole in the lower control arm i.e. this pushes the lower ball joint further to the rear of the vehicle.

All 3 cars had the caster set this way from the factory.

To check how your own car is set it very simple. Simply remove the bolt that locates the strut rod to the lower control arm. The bolt head is 19mm. and the nut is 21mm (the nut is above the control arm) but be sure to use very good tools because this sucker is very, very tight.

Racerron

I'll try to post some pics soon to make the explanation a little clearer.

It's also interesting to note that the factory uses the original 1mm alignment shim that all the GT3's have, to connect the bi-xenon headlight alignment sensor link.

Other 996's have an extra bracket for the link.

This must represent at least a 10 gram weight saving

Racerron

After reading Lynn Wilson's lengthy, knowledgable and very eloquent explanation of the GT3 vs GT3RS alignment adjustments with regard to the caster thread I still cannot see how moving the lower diagonal rod (strut rod) bolt to the rear position will give less caster.

I understand all his explanations and theories but still cannot see how the change will give less caster.

I will have to experiment on the next car I do that has a lot of shims in the lower control arm, maybe my own if the thing gets here in time for this season. The change is very simple to do and takes only a couple of minutes to check once the car is set up on the alignment rack.

I'll keep you posted.

mds

On my car I rotated the strut tops, removed the factory 1mm shims, left the caster adjuster in the factory position, and did not ovalize the holes. Camber is -2.6°, caster 7.8° and toe +0.05° per side.

NJ-GT

On my car, I have 7mm shims, caster adjuster is in the factory position (center hole). Camber is -2.5°, caster 9.05°, and toe 0.00°.

Bob Rouleau

NJ - On my car with 8.8 degrees of caster I had a tire rubbing when near full lock.

bob_dallas

Hey Bob - I'm curious as to what diagram showed 3 caster adjustment holes. The only one I've seen is the page posted by Viken in this thread that shows 2.

https://rennlist.com/forums/showthre...ghlight=camber

Bob Rouleau

Bob - I was told by the dealer that there were three holes - there are only two as you observed. Ron set up my other GT3 yesterday and tried moving the caster adjust to the other hole. It increased the caster! His theory is that using the second hole will reduce caster but only if you are using a lot of shims and negative camber around - 6 (as you would on a race car on slicks).

Based on all the info posted, if I had to do it again, I would rotate the struts 180 degrees (knock out have to be punched) and use thin shims to dial things in correctly.
He ended up using a combination of shims and elongating the shock mount holes to get the right combo of camber and caster. More shims = more caster.

bob_dallas

interesting stuff. I'm still not sure what's going on here because I have no caster problems with -2.5/-2 degrees camber

Bill - Chicago

When you rotate the struts, do you have to rotate the whole strut or just turn the monoball on the top?

bob_dallas

the whole strut