Hi,

i have GT3 LCAs all around on my car, front camber is -3, rear is -2.5 and I think, almost sure, each LCA has at least one 7mm shim. front axle definitely has.

Could anybody who deals with this stuff often enough and knows by heart how alignment works - if I remove one 7mm shim from each arm for street driving - by how much does it change toe settings? will it be toe in or toe out? current setting is 0 toe front 0.10 rear toe in.

 

Camber really shouldn't mean anything on street driving. One of my Porsches has -1 degree and the other -2.4 and both are fine on the street. Toe is the thing that can kill the tires and my shop has been doing such a good job over the years I have wonderfully even tire wear on street and track. I'm no techie, but I'd have to think you'd really screw up everything if you just took a shim out and hoped for the best. Any time you change something, you need to re-do the entire alignment so things are in balance.

 

nah, i`m not going to just to take it out, i am just curious how exactly its geometry works.
but i got to say compared to -2.4 in front -3 degrees does feel different and imho just for street it is a bit much. i then deflated tires a bit, 3-4psi or so and it helped a lot.

 

Just because you remove 1- 7mm shim each side does not mean each side will be aligned equally less. If you remove the shim you will need a full alignment...camber and toe. It is not that exact just to remove 1 shim. RonCT is correct and I just checked with my Porsche shop on this.

 

Why are you running so much camber? The 997 does not need that much even with r-comps. 2.5 max in front and 2.2 max in rear.....I run 2.2 front and 1.9 rear

 

mechanic suggested running this for a6 hoosiers i use at auto-x, this season i have killed them at -2.4 front camber, so, it is essentially a next season setup.
for v700 kumhos it has no relevance at all.
this camber setup feels great in the corners from what i can tell from 2 events i did on it so far, so, 'need' here is mostly a virtual entity. there is nothing we 'need' here, it is all matter of trial and error.

 

actually wait a sec. something smells odd here.

you say if i have 7mm+3mm on one side and 7mm+1mm shims on other side for specific camber and i take out 7mm on both sides keeping 3 and 1mm shims - camber will not get changed by same amount?

i really want to understand how geometry works, isn`t it a simple triangle there and altering shoms we simply adust one side of it?

 

On the camber/toe topic (leaving out castor), does anyone have a link to stock settings range? I should get an alignment and wonder if I should tell my mechanic "just align it" or "set it up to a medium setting for the street" or "set it to exactly -1.5 front -2.0 rear, front toe 0, rear toe...". Anyone have the stock range and recommended range?

 

stock you can get on pasm uo to -1.1 degree max, on my C2 non-pasm car max front camber was -.9, with 0.02 toe.

with 0.10 toe in in rear max camber i could get with stock toe arms and stock LCAs was -1.9 degrees. it varies a bit too i would guess as no car is exactly same as another. not very nice of you hijacking my geometry exercise here.

 

Arn't the shims for the castor changes???

 

That's what I run thanks to you!

 

so, other than regular 'you do not need it' comment - does anybody know how exactly this damn alignment stuff actually works?

i just looked under the car - cannot understand why removeing same shims on diff sides woulr result in different angle changes. got to be the same IMHO. how can it be different?

 

From what I saw when my alignment done and previous cars done, the shims are for castor changes which moves the wheels forward or backward off the center of the hub. The camber is adjusted by the 3 bolts on top of the strut mount and the toe is adjusted by the locknuts/camber bolts on the trailing arms.

On my GTO is you removed shims the castor was less which would result in less of a performance advantage on the track. I'm not sure with the 997 but I think the stock castor is in the 7s and with the GT3 LCAs it is mid 8s which is better.

 

shims i was talking about were in 2-piece gt3 LCAs. they are used for camber control. caster control is done by adjustable 'fork' thrust arms and is set to 8.2 on my car if i am not mistaken.

 

Ah. Good luck!