haulinkraut

That is the truth for sure. I am running cup LSD plates, but in 6 plate configuration to lessen the preload. Super aggressive even at 100lbs preload. The stock 8 plate is like 200lbs.

cid042

The LSD is a 2004 cup one, in stock form (as is the gearbox).

Yes, no monoball anywhere in the suspension. I do not have the ride heights at hand, but they are between road car and cup ones. It will be set as low as possible.

What I guess is that the ABS needs a lot of weight transfer on the front tyres. By comparaison to stock cars of friends, with stock (busted) LSD, and stock springs, also on MPSC2, they tend to dive more under braking, with the ABS not engaging so frequently.

I will try several springs configurations. Having had exchanges with pkm consulting and optimumg (really great people there !), trying to do the math(even if I do not understand everything), and having had a look at several track dedicated gt3, ohlins suspension options and spring proposal, and so on, I am going to use a set of 996 cup 2 ways dampers I have to be able to adjust (a bit !) to several spring rates, starting on the very soft side (70 & 160), and see if it feels better for me (and lap times ;-)). I will also take a set of 110 for the front, and will let you know.

I wonder if the technology of the shocks is a big factor too...

We have a new serie here, with dedicated 718 caymans on MPSC2. I have talked with the Ohlins guy that developped the suspension, and they really are on the soft side (not the same car, I admit ! And without the motion ratio it does not make a lot of sense to compare...), but no more than 90 at the front, if I remember correctly.

I will let you know... Many thanks for all advices.

Any geo recommandation for these tyres ?

haulinkraut

The ABS could be kicking in because you are outdriving the car's ability. A GT3 and cup have a couple of key differences that make a huge difference.

cid042

What annoys me is that I have to brake earlier than a stock 996 gt3 that is heavier, let alone that feeling that it does not really brake. The former issue may be (IMHO) caused by to few load transfer. The second one is, I guess, due to being more accustomated to slicks than semi.

Could you please elaborate on 996 gt3 Vs cup main differences, relevant in my case ? (suspension wise)

Rear tyres sizes, obviously damper and spring rates...

many thanks for all the replies

haulinkraut

Well, just for the record I do not have a cup. I have a lightened turbo on all cup car suspension. So my input is all research based from when I built my car.

Sounds you have some of the items sorted on your car. But monoball upper rear mounts, adjustable front and rear control arms. Adjustable toe links. And of course the spring rates, dampers, camber, ride height and toe that all make a pretty big difference on handling on the track. The early cups(if I recall correctly) did not have monoball rear control arms or solid caster pucks. But seems like most guys installed them latter. So if you have cup seat time it highly possible yours had rear monoball arms and solid pucks. Monoballs in the rear makes an incredible difference with all the rear weight. My car got the latter monoball 997 cup dogbones which none of the 996cups came with that I am aware.

cid042

cid042

Quick feedback from last race weekend at Dijon with the new setup :
- The braking is far better, and I can, now, modulate the brakes without the ABS engaging every time I touch them (also I have removed the brake assistance)
- I can feel the car loading its front wheels far better
- I really lack rear end grip/handling.
* I do not know if its by comparison with the Cup S I drove the same day which had too much rear (or too few front :-P)
* Or if it is the rear spring that are too hard versus fronts (or vice-versa). ARB were full soft rear, full stiff front.
* I do not think it has much to do with aero, as these cars do not seem to have much of it…

Lap time Wise : A full 3 sec better than last year, BUT on fresh tyres (sport cup 2) Vs old and tired ones last year. On a 1'30-1'33 lap.
RAce 1 : DNF ; Race 2 : 1st (in the last turn, Vs a Manthey modded 991 GT3 RS :-))

haulinkraut

Rear end grip in what scenarios? Does the rear end feel unstable, loose or like your diff may not be up to the task?

cid042

The diff seems good, no problem feeling it dealing with the frequent power oversteers.

The rear end is stable under braking, may be touchy in turn-in, and completely loose in the exit (acceleration) of the turn.

The are no really slow corners in Dijon, but it is the same in high and medium speed corners.

haulinkraut

Can you go one hole less on the rear sway?

cid042

Unfortunately not, it is full soft, and full stiff front.

haulinkraut

Then I would advise looking closely at alignment settings. With that much oversteer and body roll with the softer springs perhaps you are loosing tire contact area due to camber shift when the suspension shifts. Or perhaps toe? Honestly there are so many factor and variables to troubleshoot including driving style it is almost impossible to say for sure. Get some test laps in and make sure you are getting the same characteristics over and over. Then change something and check again.

cid042

Thanks for the advice. I will try to follow this way. The ability to adjust the alignment at the track, and limited track time will be the challenges ;-)

AudiOn19s

70nm front and 160nm rear are the springs in the car right now? That's a huge split front to rear and likely causing the imbalance issue you're seeing. I run a 30nm split front to rear on my car and like the balance of it and can fine tune with wing and shocks to get the car comfortable on any track I run including bumpy surfaces. if you like the way the front is working now I'd go down to a spring in the 110nm range in the rear.

cid042

Good point. I will dig in this way also… Thanks !