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8 minute(s) of a 612 minute read
10-25-2008
10-25-2008
There are two versions of the Bilstein PSS10's, the version that people use is called B16 Damptronic, meaning it's compatible with PASM. One thing to note is unlike the Stock settings, where Stock Normal is too soft and Stock Firm is so stiff and harsh that it becomes nearly unusable, the difference between Bilstein Normal and Firm settings is more subtle.
On a scale of 1 to 10, if Stock Normal is 1, then Bilstein Normal is around 6-7, Bilstein Firm around 8-9, and Stock Firm is 10. But the numerical designation doesn't describe the difference in dampening quality. Although the Bilstein ride is firm, the ride/dampening quality is vastly superior to Stock Firm.
10-27-2008
1. Introduction
The anti-sway bar two functions, one is obvious from the name, the other not often discussed but equally important:
A. Anti roll
B. Adjust understeer/oversteer
A is just that, the anti roll bar adds roll stiffness and prevents your car from leaning in corners. Roll stiffness is very important because it keeps the tires in best contact with the road and maximize traction (larger contact patch) in corner. More body roll also unsettles driver and conversely, less body roll subjectively is a major reason for a car feeling "good." You've hear the oft mentioned expression "cornered as if on rail."
B is related to the effect of sway bar on roll couple distribution, an all important concept in understanding car behavior in corners. It has to do with the roll and ride stiffness of the front of the car RELATIVE to the rear of the car, and how this would cause the car to understeer or oversteer. Adjustment of sway bars is used by professional drivers to affect understeer/oversteer behavior of a car. If you stiffen the front, you have understeer (as a result of higher slipped angle of front tires); if you stiffen the rear, you have oversteer (as a result of higher slipped angle of rear tires).
To reduce the inherent understeer/neutral steer of a 4WD car, for a street car, I've softer front and stiffer rear, for example soft setting front and medium setting rear, to be an excellent starting point, but of course this is strictly personal preference, no right or wrong and it also depends on the rest of the suspension components in any particular car.
2. Which sway bar?
Top 2 choices are H&R and GMG. TPC is another reputable product. As far as H&R or GMG sways: I have no idea how they compare to each other with respect to stiffness/performance. The only reason I went with GMG was at the time I was going to go with the whole GMG package (later changed my mind to Bilstein Damptronic PSS10). Also for my peace of mind, I also like very much the fact that GMG is the only company that publishes specs of the bar:
GMG Front Sway: 3 settings: soft, medium, stiff. The front soft setting is 15% stiffer than stock, middle 25%, and stiff 35%.
GMG Rear Sway: 3 settings: soft, medium, stiff. The rear soft setting is 30% stiffer than stock, middle 45%, and stiff is 60%. The GMG bar btw is made by Eibach, one of the "gold standard" companies in after-market springs and bars.
Lastly, you could use 997 GT2's rear sway bar in the Turbo, and keep the stock front (front GT2 sway bar doesn't fit Turbo). Because the stiff GT2 rear bar is supposed to be used with the sitff front GT2 bar, only using the rear obviously will result in a setup that is unbalanced towards the rear; rear is stiff (GT2 bar) and front is too soft (stock Turbo bar). The risk of the imbalance is excessive oversteer, and just the overall uneasy feeling, for me anyway, that you are using something that is not made for your Turbo. Anyway, although I do prefer and recommend replacing both bars, there are people who use GT2 bar and like it,.
Much has been made of hollow vs. solid; I don't think it's that important because this is not unsprung weight. My rear GMG sway bar is around 7 lbs IIRC, 2 lbs heavier than stock. Could you feel whether there is an extra laptop computer in the back of your car? I rest my case.
Sway bar remains the most "mysterious" of suspension components, since no vendor except GMG releases their specs and there is no review "data" so you rely mostly on words of mouth. Were I to buy a sway bar set today, my top 2 choices would be H&R and GMG. No one knows how they compare with each other, or which one is "better," however I will give the slight advantage to GMG because of the reasons above.
3. What does it feel like? The GMG sway was actually the first suspension component installed in my car as I wanted to learn step by step and wanted to find out what it does by itself. To my surprise, I found that the anti roll effect is subtle with the stock springs, NOTHING like the transformation brought on by the Bilstein Damptronic that I was to install later. At the medium settings, body lean is reduced a little, but more importantly, the steering feels tighter. There is less free play to the steering wheel as you rock it back and forth for example.
Once stiffer springs (the Bilstein) are installed, I feel the effect of a sway bar is much more noticeable. Stiffens the rear will reduce understeer/increase oversteer - it's a great educational tool for anyone of us to try out and see for yourself! One negative effect I *have* found is that the rear setting, if at full stiff could affect ride significantly. The rear becomes stiff & very bouncy and for me unacceptably hard when the sway bar is set to rear stiff.
In short, I very highly recommend the sway bar - it is obviously a critical part of the suspension setup, but only after you have installed the Bilstein Damptronic with its stiffer spring. Used by itself with the stock soft suspension setup, the effect is very subtle.
4. Maintenance IMPORTANT!!: My GMG bars come with polyurethane bushing, and a lot of people don't know that unlike stock rubber bushing, after-market polyurethane bushing must be lubricated occasionally with Synthetic Grease (Super Lube from ebay). If you don't lubricate these bushings, the sway bar may become frozen in its axis, and subsequently may cause bending of the drop links, or even shearing off the mounting point of the drop link on the coilover.
The way to test is to completely disconnect both drop links from sway bar, and then try to swing the bar yourself; it should move freely. When I checked mine it was nearly frozen in place; I lubricated it once and since have switched back to the stock rubber bushing for peace of mind. One other reason that I changed back to rubber bushing is that while the rear bushing is easy to lubricate, the front one is a pain to access. In fact I had to have my tuner Lucent change the front bushing for me. Basically I am busy with work and car is daily driver; I don't want the hassle of having to bring car to a shop to lubricate that front sway bar.
If polyurethane is such a problem, why does GMG use it? It is supposed to be more durable than the rubber counterpart. AND it does make the suspension feel firmer (yes I have switched back and forth to compare) and more planted. Very subtle, but definitely noticeable.
For those new to this topic, remember that after-market suspension components are not maintenance free. This bushing is one good example, but these other links with metallic (heim) joints also have to be inspected for wear and tear - they do wear. The inspection could be every couple of years for street use, and more frequently for track obviously. A little more work but in return, car handles with aggressiveness and that's why people still do it.
For lubricant, I've read different things so not sure, but I believe that while you could use either SYNTHETIC or PETROLEUM based grease for polyurethane bushing, you should use only the synthetic stuff, ie the Super Lube on ebay I quoted above, for the stock rubber bushing.
In picture below, black bar and black rubber bushing are stock, blue bar and red urethane bushing are GMG. The Super Lube Synthetic Grease could be purchased from ebay http://www.ebay.com/itm/SUPER-LUBE-S...-/161003162819.
