STLPCA

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by Allen:
<strong>Dan...if you upgraded all these things at once, how can you tell which item had which effect. This vast improvement in handling could have come from the springs & struts...there is really no way to know what specific impact that the sways had.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Allen
I disagree. The different components (obviously) do different things. I attribute the reduced roll & decreased understeer largely to the change in sway bars. There were other positive changes unrelated to the bars.

With prior cars (Triumphs & a 240Z), I've experimented w/sway bar installations or upgrades. The effects (all on the street w/street tires) have been profound.

911-TOUR

Allen,

As an engineer, perhaps you should avail yourself of some research into how anti-roll bars work:

<a href="http://auto.howstuffworks.com/question432.htm" target="_blank">http://auto.howstuffworks.com/question432.htm</a>

<a href="http://p-car.com/susfaq.html" target="_blank">http://p-car.com/susfaq.html</a>

FWIW, they are designed primarily to decrease the body roll in a turn - the stiffer the sway bar, the less roll - but get too stiff and you'll lose the independant nature of the suspension on each side. With stiffer springs and the smaller sways, you'll have pronounced understeer - you'll need to increase the stiffness of the bars to balance the car out.

I've now got the ROW springs w/Bilstein HD shocks and M030 sways, and the car is very close to neutral.

Hope that helps!

sean

JW in Texas

Allen,
Here's my 2 cts. worth(and that's being generous). Your mechanic is right to a certain extent & so are all the other posts that differ with his opinion. Yes, if a car has super stiff springs, like my Supercup, then most of your lean is controlled by the springs. They are so stiff they don't let it lean much. My stock bars are: Front-24 mm bar adjustable in five different positions, Rear-18 mm bar adjustable in three different positions. Not huge but bigger than your stock ones. On the other hand, you aren't running ridiculous spring rates. Tooling my car around the neighborhood will shake your fillings out. IMHO, your street/track spring rates probably need the help of stiffer bars to control your lean. <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />

Hank Cohn

Allen:

I went back to your original post before writing this response. This is a good discussion with many good points being made. I don’t want to present myself as any kind of suspension expert. I have a lot of experience with 993s on the track and on the street and have converted one to a dedicated track car with several PCA wins and a Speed World Challenge appearance. The purpose of springs and sway bars, as I understand it, is to control the contact patch of the tire. Too much lean causes the tire to decamber, reducing the area of the contact patch. Too little lean using stiff bars or springs causes weight to instantaneously transfer from the unloaded side to the loaded side, possibly overwhelming the loaded tires, (contact patch) leaving the driver too little time to react.

I don’t believe the sway bar sizes we are talking about (the turbo bars) are stiff enough to cause the worst case to occur. I do agree totally with your mechanic especially given that 90% of your car’s life will be spent on the road. Try the stock bars. They will give a better street ride especially over rough or uneven roads. Smooth roads will be the same with either. Lean isn’t a bad thing unless it is severe. We all tend to think that lean is undesirable, but a car that transfers weight slowly is very predictable and easy to handle. With the PSS9s, you have some good adjustment in the shock and can use that to dial out understeer or oversteer at the track to your liking. Sway bars are relatively easy to change and if your mechanic is going to the track with you one weekend, work with him to change bars on the second day and get a good back to back comparison. You will probably want to change shock settings as well.

Hank

Martin S.

The Turbo sways are not a major investment...I would suggest putting them on, drive the car for a month and make notes. As you drive 10% on the track, be certain to take the car to the track. You will notice with the M030 RoW bars, there will be minimal push (Understeer) with the M030 bars.

Perhaps you should go back to the shop, install the 20mm front and 17mm rear bars...drive around for another month and be certain to drive the track, or at least some very spirited street driving. Come back to the Board and report your results.

This is the only way you will really know.

From personal experience, I have the M030 RoW suspension and the Turbo sways, 22mm front and 21mm rears. I installed the sways with the shocks/struts and springs because that is the way Porsche sells them in Europe, the so called M030 package. I do about 6 DEs a year and minimal street driving. On the track, the car handles like a dream, no push and no oversteer to speak of. But that has been my experience. Good luck with the suspension...the trick set up seems to be the 993RS sway bars, 23mm front (5 way adjustable and 20mm rear, 3 way adjustable. You could run the fronts and rears at full soft, and then make adjustments as you and your mechanic felt were necessary.

In closing, I understand where your mechanic is coming from. There is an approach seen at the track by some where they tune the car's suspension with springs and shocks, and use relatively small sway bars. I have a friend who has 600 Lb. coil overs on the rear of his SC car, with 23mm front torsion bars (Stiff) and stock sway bars. His car really handles well, go figure!

Tom W

I get my car back today after converting from stock to PSS-9 and RS-sways. I chose the RS-sways as the stock allow the inside tire to be picked up pretty easily during autocrossing and the car suffered from really bad understeer. By the way, the stock are 21mm front and 18mm rear (I just went through a long song and dance to get the bushings right on the new RS bars (23 & 20).

My goal in getting the RS bars is to have something that can be adjusted for street, autox and DE to provide a car that handles well in diverse conditions. Sure it doesn'
t matter much for street use (my car is a daily driver) but the stock bars really diminished the enjoyment when I needed them most. Given how much you are paying for your cars new suspension , why handicap it when you really want it to perform at an autocross or DE? You've got the turbo bars, give them a try.

TrackJunke

A stiffer sway bar will do the same thing as a stiffer suspension up to a certain point. A stiffer suspension reduces body roll, thus reducing camber change during cornering and a making a better handling and more reactive car. This all happens up to a certain point, where putting a stiffer suspension on the car will actually reduce traction becuase there is not enough suspension compliance to smooth out bumps. This is the same principal with sway bars. A stiffer bar will increase the roll resistance of your car, and is a good thing up to a certain point. A stiffer sway bar will put more load on the outside tire when cornering and can help you to balance your car properly. My suggestion to you would be to try them out and balance your cars handling with them. A stiffer bar is not necessarily the best. As in suspension spring rates, there is a certain window between the stiff side and soft side that will make your car handle better. Anything outside that window will make it handle worse.