Nol, 95 993 C4

This Friday we will be visiting our local "track" again with the Porsche club. I've posted before how we take the Pcars to the local karting facility for fun . However, without taking myself to serious I would like to set up the car neutral as best I can, I'm not looking for overtseer. I have PSS-9's with the ROW turbo rear bar. For the first time I'll be running new (to me) 18" wheels with 225/265 N4 Pirelli Rosso's.

I'm considering to firm up and stagger the PSS-9's to 5 front and 3 rear from their current 6 all-round. However, the track is slow, tight, bumpy, dusty and low grip. Will the firmer settinhgs bring me any benefits in such conditions? Any opinions?

And then tire pressures. Ambient will be 26-30°C or around 85F. There is no opportunity to really heat the tires up properly, they will be warm-ish. I'm thinking of cold 36 rear 34 front much like a normal street set-up. Any opinions here? Should I consider this related to the damper settings?

Any input appreciated, please find a few pictures here to get a flavor of the conditions

Enjoy

Nol

Nol, 95 993 C4

one more

KOAN

Nol,
You have difficult conditions, and I'm eager to learn what others have to say. A bumpy, slippery surface is a tough one to conquer.
I would consider your surface like a wet surface...poor grip. The best bet is to maximize the contact patch, and reduce the lateral forces that the tread has to contend with relative to the road surface.
A stiff suspension will increase the demands on the tread, but might lessen bounce on the rough surface. It will also attempt to increase the surface area by forcing the inside tire down. Although these opposing tendencies are difficult to control independently, I would modify the adjustments to a softer setting, and thus lessening the lateral stresses. If you have adjustable sway bars, I would soften them. I like your idea of a stiffer rear bias, so you can get the car rotated on the tight track. The nice thing about the PSS9s is you can modify them and tune them at the track.
I'm eager to hear what your conclusions are after driving. By the way, those are cool trees in the background of your track pictures.

Chuck

Mark in Baltimore

Nol,

Oh, sure, throw it in our faces.

Nol, 95 993 C4

Chuck, thanks for confirming there is a compromise to be struck here. you can see where the dust comes from, we had 25 knots wind out here just a few days back. If you look carefully you can spot the odd golf cart, as that's looking onto a golf course. Those trees are shaped by the "greenkeepers" assisted by the local herd of goats .

Mark, you're welcome.

Enjoy

Nol

kary993

Nol,

I would add to Chuck's comments that if you have a track that has more right or left turns you can set the suspension setting differently between sides to help with bumps and grip. Most bumps tend to be on one side or another coming into and out of turns so you can adjust the car accordingly. You must weigh in the upside versus the down side depending on how biased the track is to right or left turns.

Just another though for you to ponder!

Nol, 95 993 C4

Kary, thanks, the track is biased to right hand turns, but I feel this would be taking it one step too far for the intention of the event.

Any ideas on the tire pressures or PSS-9 settings?

Enjoy

Nol

FlyYellow

Nol,

my 2 cents based on my experiences...

i would soften up the suspension to near full soft in the front.
i would keep the rear mid to tight. (can u tell i hate understeer - especially in slippery conditions)

my theory here is that the softer front will allow your shocks to absorb some of the bump and slightly improve turn-in for a tight track.

on a slippery track i would probably run mid tire pressures (especially since they don't get a chance to get too warm). reducing the tire pressure will give you more meat on the ground and improve handling but if you never get the tires to proper temp then it becomes useless.

kary993

Nol,

Need to know tire sizes and type of tires and possible air/track temperatures to help answer your questions.

JohnM

For me, 34 cold for the 225 fronts is much too high, you would be better off starting at 30 front. 36 rear cold for the 265 is OK, but you will probably have to drop the pressures on both as you get heat into the tyres - I usually aim for hot temps of 34-36 front, 38-40 rear. Would be interesting to hear what other people aim for as hot pressures for the N4 Rosso. Despite your comment, at 25-30C ambient you should be able to get plenty of heat into the tyres! (but what do I know, in the UK 30C is practically a national emergency ).

I've also had great results running 6 all around with PSS-9 even at the track (as I run on the road, because I coudn't be bothered to make the adjustment), but that is with RS bars. If the track is bumpy and slippy then setting the dampers harder would seem rather counter-productive.

Nol, 95 993 C4

Thanks guys for the feedback,

So far I sense that increasing the front to rear staggered stiffening is "list approved". And it was indeed a post by Steve W himself that planted the seed for that plan. (I don't do it for daily driving where a bit of understeer suits me fine)

Stiffening overall however might not be the best compromise. However, I feel I may have overstated the bumpy part a bit in the opening post, though it is definitely slippery and dusty. That is why I wanted to try and turn up the damping on the PSS-9's a notch. Not decided yet then...

About the tires, well there really is not enough track time to put heat in the tires. I think of it as a low grip street situation, just not not cold with the climate we have here. Kary you'll find the tire details in my opening post. Just not the track temps, I have no idea of them.

Boris, could you elaborate on what you consider "mid" pressures? and I'm also do not quite sure that I understand how softer front damper settings will help the turn-in. I think I would have guessed the opposite effect, tightening up for sharp turn in?

JohnM You seem to run the rear pressures slightly higher than my current. Is that for the handling or some other compromse (comfort, pot holes). And thanks for the feedback on the PSS-9s. I've been running all 4's with same mid settings most of the time and I like it. I did not get adjustable sways, I'm confused enough as it is. The quest for my personal "perceived neutral" set-up continues.

Thanks and Enjoy

Nol

BTW the first time I accidentally oversteered out of one of those tight slow turns (aged tires gone hard) I was not sure I actually liked it. It did take some getting used to the sensation. The next lap I had a milder version of the feeling in a couple of turns. I (again accidentally) must have hit the sweet spot and the car felt like it slingshots out of a slow turn without wrestling the steering wheel for push and the seemingly seconds of holding back on the throttle. Yeaaah.

kary993

Nol,

I should have re-read your opening post. Lots of info there. Sorry.

At any rate, I was wondering just how long of a lap is your track, in terms of time? If it is around 60 seconds and the turns seem to be quite tight from the photos, I would set your front PSS9's to about 7 and your rear PSS9's to about 3. Set your tire pressures front 30 cold, rear 35 cold and see how she handles. Ideally you might see about 34 hot and 39 hot front eh rear tire pressure after running 3 to 5 laps.

If she understeers stiffen the rear PSS9's to 1, and/or add a pound or two in the rear tires.

If she oversteers soften the rear PSS9's (and/or stiffen the fronts to 4 or 5), and/or add a pound or two the front tires.

I think you see where I am going here. You will have to be the judge at the track to decide how much to go one way or the other as the situation presents itself.

Note: this can all be dealt with more simply with some adjustable sway bars. May be a future purchase?

FlyYellow

Nol,

good question on the turn in - i may very well be wrong on this one, but my theory (let's see if anyone else will share their theory) is that when you don't have traction (i.e. rain) a softer suspension will allow you to use the weight transfer of the car (since it should sway more) to turn in, rather than using your tire grip (which is too slippery in the rain) to turn in. i'd like to hear other's opinions on this one.

as for mid tire pressures. i run the michellin pilot sport cups. i found that in the rain i can run 34/f and 38/r. in dry sticky conditions i run 29/f and 32/r. i base this on a slide deck from michellin that i got.


if anyone wants a copy PM me and i can send it you via email.

Cheers,
Boris

JohnM

Nol, I think you may need to change the anti-roll bars to get the most neutral balance. I ran PSS-9 on my C4 with stock bars for quite a while before getting the RS bars, the RS bars were a great improvement - particularly in sharpening the steering response. If you do go that route, the following may be helpful: with 225 F and 285 R (I haven't tried a 265 rear) the car was fairly neutral with front bar full soft, rear bar middle - just a little understeer in the fastest corners (not necessarily a bad thing ). However, with the front bar full soft I found bump-steer effects on turn-in (I guess due to too much front roll) to be unpleasant (at RS ride height). I tried front bar middle, rear bar full stiff - lot of understeer compared to the soft/middle setup. So now I've got the 245/35 Rosso on the front, and first impressions are that it has nicely moved the balance towards oversteer even with the front middle/rear stiff bar settings. I won't get on the track with this setup until March, though (assuming its not snowing then ).

Nol, 95 993 C4

Kary, the lap is one minute indeed. In the current format we get 3 laps at a time with the second lap being timed. If you are right I should see some marginal increase after the first lap. I think I will set up the tires to almost the desired hot pressures. Your PSS-9 recommendations are to stagger by softening the front as well as stiffen the rear, ie adjust both ends compared to street set-up.

Boris, thanks for the explanation, and your pressure data wet vs dry is very interesting. I can imagine much of the difference is down to the cooling effect of water on the tires. IE your hot pressures are not too different dry vs wet, what do you think. If I think of it that way Kary's and your pressure recommendations are similar. BTW both of you are in C2's too.

Now John, reading your signature line in full, I realise that my earlier query about comfort or potholes was somewhat off the mark. That C4 of yours has all the ingredients of a proper track tool. As for bars, I have the stiffer rear Turbo bar to add some stffness to the rear, but that's it. Now if you have oversteer with 245/285 Rosso's on staggered RS bars, and I know it pushes with 205/255 Michelins on my bars. I reckon 225/265 is a good step in the right direction.

What hot pressures do you aim for with your set-up?

Like I said, I don't want oversteer just now, I'd like to go more neutral, coming from understeer. Take it one step at a time. So the adjustments compared to last event:

was: 205/255 MXX3's 32F/34R PSS9 6F/6R
now: 225/265 Rossos 34F/37R PSS9 6F/4R

I think ths will take me a step in the right direction. I tend to weigh John's comments on his C4, but I deviate in staggering the Pss-9's, just less than the C2's recommend. I'm now leaving the front PSS-9s but will stiffen the rears. And I'm aiming for some higher pressures as if I were running in the "wet". (I also remember how a few laps at this track used to scrub the outside shoulder of the threads quite significantly, this also supports running higher cold pressures)

The advise so far is fairly consistent despite some clear differentiation. All we are missng now is someone to completely disagree with the opinions above Great feedback once again, and despite being separated by many timezones we managed to keep a nice thread going so far. The List rules.

Thanks and Enjoy

Nol