Macca

Joe. Ive been thinking about this.

When I adjusted my camber from -1degrees3'/-1degrees3' to -2.0degrees/1degrees54' (degrees and minutes not degrees and decimal) I had before and after taken and was at pains to tell my Geo guy I didnt want the castor to change significantly. He recorded the before (factory after 3500km road) and after. I was told by my Porsche Tech 9.30" was the target for the factory set up. No shims were used this was the max deemed possible by my long standing Geo technician and wizz.

As you can see in the first slide below we more or less kept that with the front right (passenger in USA, driver side in RHD) moving out a little by .06 minutes. Interestingly its this side that I have a very small amount of polishing n the liner just where the bracket you highlight is. No where near wearing through the plastic I might add after almost 12,000km and 4+ track days and alot of fast back road driving...

Over the last 12 months I have collected around 6 people on here initial and final geo settings. Guess what? They all show around 9degrees30" castor from factory!

But along the way I collected a slide from someone who told me this was from the factory manual and it shows 8degrees30" as the factory specified setting! Then just today I learn that this is also the recommended setting from the earlier gen GT3! Im now wondering where this slide I have came from and whether it is correct? I have done direct to German to find out and should have an answer overnight.

Im of the belief right now the car was set up with -1degree30" F+R camber and 9degrees30" front castor from the factory!

My belief right now is that you have over corrected castor. I believe if you are at 9degrees30" or fractionally below you will reduce the oversteer you are feeling and find a significant shcnage in teh chassis. You have corrected almost 3 degrees of front castor which will effectively change the wheelbase, making it shorter. Just a hunch but have a look at the data below and make your own decision....

So we need the real data from the factory to understand what front castor should be. This will tell us if 8.30 is correct. Evidence I have from half a dozen data points suggests factory sent the car out with mid 9s!

P.S. manifold - like you I am considering setting all back to stock before my next track day. Ive just had new MPSC2 N fitted, new Endless MX72 pads (silent on the road), new steel braided lines and SRF fluid fitted last week and the car is now in storage till September when I have 3 track days over two weeks. Id like to try the factory settings for once as I went to the more aggressive ones so I have little on teh track to compare to but with my mix of usage Im always going to wear the insides faster than the outsides unless I get very aggressive with camber and probably compromise fast road enjoyment...

First slide mine before and after.

Other slides other people on here geo before and after (all in the mid 9s)

last slide the "factory" settings posted by another on a board. Second to last is the earlier Gen factory settings (see the 8.30). With the longer wheel base and effects of RWS Im wondering if the 991 GT3 should be different...

orthojoe

Macca, thank you very much for this. It does appear that caster has been over corrected. The value of 8.3 I used was taken from a piston heads post and also based on what the 997 setting was. I know dobaS had caster of 9.3 from the factory as well. When the lca Monoballs go in, I will have caster corrected to 9.3 unless you discover something different. Thanks!!

Manifold

I don't recall the exact number, but the caster for my car was/is also above 9, before and after increasing camber. With the stock suspension, apparently caster can't be separately adjusted (but will increase when camber is increased).

orthojoe

Correct. Caster cannot be adjusted unless you install an adjustable thrust arm bushing. It is recommend that you get monoball lca ends as well if you go this route.

Mech33

I don't understand the need for monoball ends. The adjustable thrust arm bushing is allowing you to get the lower control arm geometry back to stock lengths, so stress in the bushing should be lower than before with big camber and out of spec caster.

sasportas

Just noticed the "Plano" alignment.

Are you sure that you like "toe out" in the front?

Car is usually a bit more settled with "zero" toe upfront.

Caster adjustment via thrust arms / adjustable pucks is essential in order to avoid destroying your wheel liners and making the car more difficult to turn when you've adding more negative front camber.

ChrisF

We're all getting our pipes pinned so we don't belch coolant and spin you into a wall

orthojoe

We thank you for that!

MayorAdamWest

:-)

I've noticed the same as Joe. I've been seeing a lot of 991 GT3s at events. I've never been the only one. Very very few older GT3s. Maybe those guys are too busy fondling their shifters?

Macca

Factory documents front castor as 8 degrees +/- 30 seconds. Max difference left to right 15 seconds. Vehicle with full fuel tank but no driver. Now Im stumped as Ive not seen these values on a stock car at least according to the geo sheets myself and others have!

here are the requirements for set up:

Manifold

Similar for me.

Last event I went to (Chin WG), IIRC there were four 991 (all white!), four 997, and one 996.

At an upcoming PCA event at WG, I count eight 991, nine 997, and four 996.

MayorAdamWest

That's a lot more 997s than I see, likely because it's PCA. I haven't been to a PCA event, nor do I have plans to do so any time soon.

orthojoe

Interesting. That is quite a mystery.

I can't speak for GGR since I've never done an event with them (I hope to this year), but I can tell you the Diablo group is well run, very friendly, and they won't make you jump through hoops. They let me in the advance group my first time with them, and I also saw them quickly demote someone that didn't belong in advance without any drama. More track time and open space than any other group too!

dntlvet

Yes, so sad.

mooty

diablo region is great
GGR is very very good too. TSmith is the DE chair and is on RL here. joe, if you tell tim you are orthojoe, i am sure you be in advanced group. they dont want you to scare the lower group lol.

personally i would take GGR over ANY organization in nor cal, well. other than mooty day of course

case in point, after joe's day at TH, i am towing straight from TH to LS to attend GGR. and likely i wont even pass sound.

yes, i drove with every group up here. HOD when it's called ray's day. TMR when it's a one man show, NCRC before it's called NCRC. SV, lotus days, nasa, audi club, bmw cca.... u name it, i have driven it.