rshanholtz

Does any one have a 987 Cayman or Boxster with Qualfe LSD and Bilstein PSS9's on their car and ..have tracked it? I just acquired this car with this setup and yesterday was my first day on my home track with it. My previous track car is a modified 951. The Cayman S has pronounced unpredictable oversteer at and near the edge. I purposely went out on stock ZR Michelins PS2's to get to know the car. I experienced this unpredictable oversteer in both left hand and right hand turns. It is not quite snap oversteer but as close as you can come to it. I went out with our Club Director who is a former professional race car driver and at 10/10's felt and experienced the same thing. We both described it as a tire patch problem like the car is rotating and losing tire patch as if the camber is off and something is also simultaneosly causing the wheels to shimmy. Has any one experienced this and if so, what corrective action did you take? I spoke with FBL before I took the car onto the track and they suggested that I replace the front control arms with GT3 control arms as they are slightly longer and adjustable adding natural camber and allowing for proper geometry. Additionally it changes the puck from OEM Cayman as the stock puck causes shimmy when threshold braking. FBL also recommended changing just the puck in the rear control arms for the same shimmy problem. Any suggestions or thoughts are much appreciated.

FTS

Do you know the setup of the LSD, lock up on accel and decel? Also do you know the PSS9 setup in terms of spring rates, or is the usual out of the box PSS9s?

Few people did experience such oversteer on corver exists with GT LSD with even stock setup, I thought it is mostly too agressive throttling and not being used to having true LSD, but I probably was wrong. I haven't tried a CS with the GT LSD actually to feel the difference.
In terms of the front control arms, I think adding camber is definetly useful, but do you really need it? The strut tops with PSS9s are not adjustable? I changed the rubber bushing on the front (the 'puck') and the shimmy is gone.

Dave DE

I suggest having the wheel alignment checked. Lowering the car with the pss9's has a big impact on toe and camber at both ends. Could be they weren't set where they ought to be. One of the nice things about the box/cay platform is how stable and predictable it is. If your car isn't that way, something is wrong....

Driver8

If the car does not have GT3 control arms or adjustable camber plates, then you are not able to dial in enough camber up front.

I agree with Dave DE, start with finding out your alignment setting.

rshanholtz

Thanks guys. I do not believe the car was setup for track use but rather for street use as the pitch of the front and rear wheels looks identical to my stock 06' C2S. The car was lowered when the Bilstein PSS9's were added. I think the Qualfe LSD allows the car to rotate better which only amplifies the problem. If you do not have LSD, the stock Cayman S will not pull around the turn but rather the inside wheel will smoke (see the Stig drive the stock Cayman S on Top Gear). I will have the setup redone, check the setting's on the Pss9's and do the front control arms and replace the rear control arm's pucks. I am also considering the GT3 Sways as they are thicker and lighter. Thoughts?

tkerrmd

also must remember driving at 10/10th's with street tires and a street alignment may have alot to do with it. A proper negative camber and R compound tires may be all you need to correct this. Also was the front or rear sway changed as this would factor in as well.

rshanholtz

The sways are stock and I am considering upgrading them while I am doing the control arms. I have an appointment with FBL for next week to look into everything. I also think the PSS9's are set too soft. When we put the car into sport mode and turned off PSM, the car went faster before having the unpredictable over steer which is bad as we were at an even higher rate of speed. If the over steer was predictable, I would agree about the R compounds but since it is not, then I lean toward improper camber and something loading or unloading improperly back there.

gmsracing

The Cayman requires bar adjustment to correct the handling after installing an LSD/TBD. Porsche changed the bars on the '09 cars for this reason. Basically you've decreased your rear lateral grip levels at the limit because you can apply the power sooner/more efficiently. Check over at the Cayman club for the recommendations. I have PSS9's without the LSD (lowered ~ 25mm) and I've maintained my normal balance on the street and track. I have a very slight understeer at the limit (which is fine for me) unless I do something stupid. I decided not to got the LSD/TBD route because I didn't want to have to get bars too at this time.

Krokodil

Was the car bottoming on corner exit?.

Most folks set the car too low for the stock PSS9 spring rate. Running out of travel can take away grip very fast. Also, setting the car too low, without correcting the rear geometry with adjustable toe links and create major bump steer and snap oversteer.

A Cayman with PSS9 and the Quaife TBD can be set up properly to run fast and predictable. Set the ride height just a bit lower than stock (minimize increase in roll couple). Use GT3 control arms in front to allow proper camber adjustment; install the GT3 front bar and Tarett rear bar with Tarett drop links; and have a proper corner balance and alignment. You can play with the bars to tune, but the car seems to like one from full stiff in front and one from full soft in the rear (full soft in the rear if possible as this aids the Quaife in getting traction on exit). This is tire and camber dependent or course.

I race a stock weight (3220# w/ driver) Cayman S in POC Improved (LI/R6) with this setup and have been able to win a few races and set some respectable lap times (1:42.0 at Laguna Seca, 1:53.2 at the CA Speedway Rovel). YMMV.

Cheers,

rshanholtz

Awesome and thanks everyone. The car is scheduled for adjustable front control arms with wish bones, rear control arm puck replacement, tarrett sways and drop links front and rear, an adjustment to the PSS9's, proper setup for DE/track, and a corner balance. I am back out at LRP on Oct 17th and will let you know how everything goes.

jumper5836

Cool, let us know how it goes.

gmsracing

Double check the minimum drop recommended by Bilstein--I don't remember the value off the top of my head but when I called them to discuss my installation they said there is a range (and minimum) the suspension is designed to drop. I was actually playing around with that at the time because I was trying to get some more clearance for a rubbing exhaust.

rshanholtz

Forgot to fully answer Krokodil, the car did not bottom out any where on the track. Thanks again everyone. I plan to call Bilstein today or their minimums. The PASM Failure lights keeps coming on now also. I am sure all of this is connected somehow.

BGB Motorsports

The Quaife will behave like an open diff if you're NOT on the gas. There is no lock-up off throttle. Upon initial throttle application, it's not going to lock up like a clutch type LSD either. You won't get that initial diff induced push. I found out today that guys seem to like the typical 40/60 clutch diff that's in most 911 track cars.

The deal with the pucks in the control arm is to replace them with something harder like delrin so that you don't get the suspension deflection under braking...sudden toe changes etc.

As for the 2 piece arms, if you've achieved your desired camber settings without them, you don't need them. However, if you can't get to your desired camber by slotting, camber plates, etc., then you'll need the two piece arms so that you can begin adding and subtracting the shims that split the two arms in half.