David C

Help. I recently installed PSS9 system on my '95 and I'm fighting bothersome understeer. Started with a 5 setting at all corners and now are at 7 front and 4 rear. Still understeers under heavy throttle. My car has factory sport sway bars. Do I need RS bars (or aftermarket) or should I keep stiffening front and softening rear?

Greg Fishman

I think the higher the number the stiffer, correct? In that case you need to reverse your settings. Try 4 in front and 7 in the rear. Also double check your sway bar mounts in the rear of the car and make sure it is connected.

Increase rear stiffness will equal more oversteer/less understeer. Reverse is true for the front.

Eric in Chicago

The set up for PSS 9's is: higher the # the softer the setting. For city driving I set 4 front 6 or 8 rear. This gives me a little better city ride. Greg's idea is right on, go softer in the rear for less understeer. Adj. sway bars can fine tune the supension, but if your not tracking the car, I think they are overkill (I now have racers group adj. sway bars and only move them around a few times a year for the track)

C4S

As usual, Eric and Greg are both right- softening up the rears will help. I do not have sway bars either (yet) but I do have rear monoballs in my car. For the street I set the rears to full soft #9 and the fronts to about #7. The car seems to handle fine for the street and with the softer setting, the ride is much more comfortable.

Greg Fishman

Guys,
I think we got it reversed here. To increase oversteer/lessen understeer you want to STIFFEN the rear, soften the Front.

David move the rear shocks to a lower number (stiffer) and see how that works. Make a large change, and then fine tune.

C4S

Greg- I think I got it confused. This is another good resource that should help explain everything (thanks Steve).

<a href="http://www.rennsportsystems.com/~porsche/1-e.html" target="_blank">Rennsport Systems- Chassis Tuning and Mods</a>

To Reduce Understeer or Increase Oversteer
Suspension: Soften Front
Stiffen Rear

bet

What are your alignment settings? I assume you had the car aligned and corner balanced after installing the PSS-9's. Did you specify alignment settings or did the shop just use the “normal” 993 alignment settings. From my understanding the “normal” factory alignments specifications for the US have inherent understeer built in them. I have never heard of anyone really complaining about understeer with the PSS-9's and that is probably due to most choosing to go with the RS alignment and right height specifications which are more aggressive (less understeer) than the US settings. Just something to check.

Eric in Chicago

I think I need to finish my coffee before I post <img src="graemlins/c.gif" border="0" alt="[ouch]" /> early in the morning....

Martin S.

I really don't think adjusting the shocks is going to cure understeer...if it does, please let us know. You have the Sport bars...they are not adjustable, so all the striffen and loosen advice we give you is moot. You can go to the RS bars that are 5 way adjustable front, 3 way adjustable rear, a sweet set up, but you will spend $1,000 to get your hands on them.

If and when you have tried all the available combinations of shock settings on the PSS9s, and by chance it doesn't work, you can add a 21mm 993 Turbo rear sway bar, and have your favorite hole drilling shop add one (1) additional hole ahead of the standard hole. If you still have understeer after the 21mm bar is installed in the standard hole, re-attatch the drop link into the added attatchment point. I believe the cost on the bar was around $200.

I have this set up on my car...22mm front bar, 21mm rear bar, added attatchment point..no understeer to speak of. Also note with the 21mm bar, I have yet to reattatch the bar to the added attatchment point. The 21mm rear bar did the trick.

I do track the car so I have had the opportunity to visit understeer...she wasn't home with my current set up.

David C

Car was aligned to RS specs. Ride height was set at LF 142, RF 140, LR 121, RR 121. Corner balanced (with 165 pound driver) LF 951, RF 644, LR 968, RR 929. Thanks for all input.

KC993

Agreed with Martin, get a 21mm rear bar and you don't need to change the drop links. If still pushes get a RS adjustable front bar.
I have a C4 w/PSS-9 and that's what I have on right now.

kary993

In my opinion, if you are using stock tire sizes there is your understeer problem. What are your tire sizes?

David C

Yep. Stock sizes... Conti Sport Contact 2. I recently chose these after several sets of SO-2's. Certainly not as grippy.

JohnM

If your understeer problem is at the track and the tracks you are on are well surfaced you will find little change from damper settings, will only be really noticeable for fast turn ins or in tighter chicanes with rapid direction changes.

Your front/rear tyre load distribution is governed by anti-roll bars, springs, front and rear ride heights and throttle position - the last one is easiest to adjust . I find that in the tighter corners I have to stay off the throttle until the apex, feeding in the power before that just means running wide. It feels dead slow and like you are waiting forever to get back on the power, but gets you out of the corner quicker and round the lap faster. If you are struggling for grip generally, even in the medium speed corners, make sure your tyre pressures are not getting too high during your sessions and/or get grippier tyres (I have SO2's, they are only good for about 15 minutes at a time then they start to slide a lot and if I stay out they end up looking pretty 2nd hand).

Viken

[quote]Originally posted by Martin:
<strong>I really don't think adjusting the shocks is going to cure understeer...if it does, please let us know.</strong><hr></blockquote>

Martin, what are the adjustable shocks good for, then?