Hello there...Until last week my car had OEM shocks with Techart(eibach)springs...Great look but a little soft when pushed...Especialy with k24/18g it felt VERY soft and unreliable...So it was time to do a suspension mod...
To my previous porsche cars,I always installed Porsche Sport Suspension,and was very happy...However these cars were not lowered as much as with the Techart springs...After a lot of search A decided to buy PSS10 with GT3 sway bars and adjustable swa bar links...i placed front PSS to 3,sway bar to 2(out of 5) and rear PSS to 6 and sway bar to 3(out of 4)...and went for a ride...To be honest i did not like the car more than before...the front end tends to go up and down in speeds over 140km while in turning,the car seems to be divided in two...front end feels seperated from rear end...it scared me...also the level of traction at rear wheels seems lower than before...So I turned PSS front at 6 and rear at 8....things were better but again the front end dance a little while the car does not turn as one piece...Has anybody a cure for that?did i do something wrong?(of course the car was very carefully alligned to factory specs...)Previously the car was understeering while now understeer is dissapeared...but rear end tends to loose traction easily...

 

IMO, the best thing to do is pay a known race shop to set up your car for you. They have the experience to put all the parts of the puzzle together and make them work together optimally. Good luck.

 

+1 for Larry.

With all these changes, you need to go have the car set up properly. This will include making sure the rake is right (usually 1 degree nose down), corner balance, and an alignment that haas more camber than factory spec.

 

Thanks guys...alignment with +1 degree camber than stock...interesting...

 

Uh, no, that's not what I meant. +1 means I agree with him. In general, you need more negative camber to make the car handle better. But it's a trade-off for the street.

 

when you say the rake should be ok,you mean when the car height has set up there should be 1 degree angle between front and rear axles?

 

I assume you had an alignment done...corner balance would be best. If you installed pss10 and havn't done this...your settings will be all over the place. This is not optional.

Should have read your post more carefully...I see you did do alignment. You might want to align to GT2 specs if you lowered much...are you aligned to X73 specs?

 

I degree rake means that the *body* slopes down by 1 degree. You can't change the angle between the axles unless you use different size tires.

I mean no offense, so please do not take the following comment that way. Your questions suggest that you are a little confused about how the suspension works. I highly recommend that you find a primer on suspension setup and read that before you go much further.

jon

 

In the next days I will write a complete write up about PSS10 in 996TT...Data are awesome...the car was driven in monday on the best race preparation suspension centre and hopefully it will be ready in friday...However now I need someone to tell me what is the best ramp(nose to rear end angle) so to set up the car height properly...I read about 1degree the nose lower than the rear end but this tends to set the rear end at 4cm higher than the front nose...(tangent of 1degree with a wheelbase of 235cm of 996)Any data?

 

You need to have it corner balanced. This will set the rake properly. The PSS10 is a very good street suspension, but it's not up to track use. As the other board members suggested, take it to shop that knows how to dial in the suspension for your intended use.

 

I did so and the results were not good...I ve had the PSS10 shocks measured at all ten scales of bound/rebound as well as the stock shocks.
1)pSS9 had a linear adjustment...
pss10 does not have an accurate linear adjustment.At scale 1 (front)it has 105kg rebound.2 goes to 109 3 to 114 4 to 117 5 to 120 6 to 124 7 to 128 8 to 132 9 to 138 and 10 to 200...The stock one has 185...so in order to have a suspension with stock stiff you have to place it to 10!!!What is the reason for adjustability then?

 

You are forgetting the springs...those were changed, too. Hopefully someone who knows more about suspensions and handling can speak to this.

 

I have PSS9's on my car which are almost the same thing. At the track, I set mine at 1 for the rear{your 10} and 2 or 3 for the front{your nine and 8}. For street, I set the fronts to 8{your 3} and rears to 7{your 4}. The PSS9's ride smoother than stock on the street at this setting. At the track, the stiffer settings kept the car from wallowing in turns. My Porsche tech has told me the rears should always be set stiffer than the fronts to minimize understeer. Good luck sorting this out.

 

Corner balancing will not set the rake properly. When the car is corner balanced, the ride heights are tweaked to try to equalize the cross weight (LF + RR = RF + LR). The rake is set first to be roughly what you want it to be (1 degree nose down is a reasonable starting point), then corner balancing fine tunes it.

As vehicle speed increases, the static rake decreases due to torque applied on wheels to counteract wind drag. It is also affected by spoilers, front and rear spring stiffness, etc. Yeah, it's really complicated, and there is no simple formula for getting it all correct. There *IS* a reason that all the race teams spend a lot of time futzing with the suspension settings before and during races.

 

I'd recommend that you set the suspension up properly before assuming the suspension isn't working well for you.

As for the rake, I'd shoot for GT2 settings. The FSM calls for 118-123MM of adjustment at the middle bolt head on the strut bar mounting location at the front chassis. The rear height should be 133 - 138MM checking the height at the dowl locating hole on the rear subframe (next to the rear lower control arm inner mount on the subframe). That variance should get you the rake needed. I'd also recommend adjustable swaybar setting as such: rear middle to full stiff, track dependant and fron set to full soft. I'd run the coilover settings at Full stiff (10) on the rear and two clicks off full stiff (8) on the front.

All this is assuming that you're getting about 2 degrees negative camber rear and 1.5 degrees negative camber front on a street alignment, which will still be aggressive for street use, but not optimal for track use. If this is a full track car, you'll need 2.9 neg. front and 2.5 neg. rear and plan to buy some more bits to dial the caster back to normal.

Also, all of this assumes you've done a weight/ corner balance.
Mike