I posted few days ago about the single Bilstein PSS9 I dynoed. At that time I warned that the results may not be representative, as I was still waiting for results of the second shock. Now that I dynoed both, I can speak more openly.

I believe that this problem is affecting all B5 PSS9s and potentially all PSS9s.

Here are the dyno results for the front and rear shocks:

<img src="http://www.startupracing.com/images/Suspension/BilsteinFront.jpg"><img src="http://www.startupracing.com/images/Suspension/BilsteinRear.jpg">

As you can see these shocks only offer two adjustment settings, not the 9 that are commonly advertised. There is no difference in the shock performance in the middle settings, only the two extremes matter. I also believe (and this can only be proven by track testing) that these shocks will deliver harsher ride and sharper response at the stiff setting, but with that much rebound less traction and ultimately slower cornering speeds.

I was hoping that with the PSS9s we had a good offering in the sub $2,000 range, but I am confident now that Penskes and Ohlins deliver quite a bit more value.

Until proven otherwise I believe that there are two generic categories of coilovers there: low cost, high durability street optimized twin tube coilovers like Vogtlands (my preference) or Konis, and high cost, rebuild able, race track optimized mono tube coilovers like Penske and Ohlins. Both will deliver lots of value per dollar. Unfortunately the middle ground seems to be a compromised solution... acceptable to many, but still a compromise.

To get the above results I had to spend little over $200. If you are interested in having any other shocks dynoed, please e-mail me. Maybe we could get small donations from a group of enthusiasts and dyno few more offerings. To kick this off I want to share the results from dynoing the B5 S4 Vogtlands:

<img src="http://www.startupracing.com/images/Suspension/968417Front.jpg"><img src="http://www.startupracing.com/images/Suspension/968417Rear.jpg">

compared to the street coilovers you mentioned IMO. Sure you dont get perhaps a full range of 9 settings but as you can see on the stiffest setting the valving is doing exactly as it should. It is easily able to surpase the street setup like the vogtlands dynod there as it should with its slightly higher spring rates making it not pogo like most of the street setups I have tried that rely on much smaller dampers. The handling is fantastic for track duty and the street feel is only slightly more harsh than the OEM S4 suspension as those members will report and I have seen (quite a bit stiffer than the OEM non sport suspension of an A4 though). Then if you prefer the feel of a soft spongier ride for the inlaws when in town you just crank them down while still on the car and you have an almost non sport suspension feel. For $1450 (the price now Autozone and many other sites are carrying them for) it really was the only way for me to get a performance level similar to what I wanted but not having to pay almost 4 grand. Would I prefer a motorsport kit? Sure I would. Would I prefer street coilovers? Not at all. Even for confort I find the PSS9 is fantastic and it really does perform well on more harsh tracks.

cheers! Mike

Just wanted people know what I knew though.

FWIW, today I changed my PSS9s from "3" to "9" and noted a difference. Significant? No, but it did come out in road undulations and freeway expansion joints.

I don't fully understand the technical discussion here, but I would like to understand what was done and how changing the dampening would have an affect on spring rates.

Can a Bilstein representative be contacted to comment on this as well?

Graph shows the force in lbs. that the shock excerts at different speeds.

Key here is that PSS9 does not change between most settings. It is what it is. Not judging here.

separate line show that the shock is working almost exactly the same for all but one setting.

the single line with a very different path is the "other" setting of the 9 options. the remaining 8 are following the same trend-line. actually one line may be deviating, but it's pretty much going to feel the same.

I think PSS9s have enough rebound to accept a stiffer spring, you could add about 100 lbs without issues. If you crank up to stiff, you could add 200 lbs or more. The problem is that stiffer springs require softer compression settings. Bilsteins add compression at the stiff setting. I do not understand that at all...

I am not kidding. Bilstein springs are custom to this app, and shocks are not user rebuildable.

actually keeps one set at BS USA and one set on the car and communicates track results over the phone with Steve as he sets up their valving and ships out the set to them. He has been helpful to me in the respect before. There is a cost for the revalve though. As for spring rates. Bilstein reports the setup is good for 650lb springs with no need for a revalve at all, perhaps more but they are not willing to commit.

cheers! Mike

Tein says +/- 110 lbs on their shocks from what the original spring rates were.

rather than try and push me to do something more daring. I'll do that all by myself :)

cheers! Mike

You've only got graphs for at one speed, a relatively slow speed of 5in/s.
Perform testing across the board from 1inch/s up to 14 or 16inch/s, and I'm sure you'll much clearer differences between the various shock settings.

In street cars you rarely get anything above 5" / sec. rumble strips... maybe.

I will test it again...

They could differ at slower speeds as well.
Testing just a single speed only gives you a graph at that speed, nothing else. You can't necessarily infer that the shock will behave exactly the same at every other speed.

If we're trying to fiddle with the car's handling, under 5"/sec is where we're likely to see an effect. At the higher piston speeds, you're only likely to see an increase in ride harshness and loss of traction.

To say that these shocks simply "have 2 adjustment settings, not the 9 advertised" is probably very premature to be saying without testing the shock at more cycle speeds.

I'd agree most of the suspension movement is relatively slow, but by no means is suspension only limited to 5in/sec motions.

many small surface inturruptions. I'm surmising that you want the shock to be able to hold up in all situations for optimum handling and ride. cheers! Mike

Shock do not start acting differently at higher speeds. The lines would begin to diverge at lower speeds, and the difference could be more pronounced at higher speeds.

Also look carefully at the colors. On the fronts red and purple are closer on the rebound side, while they are at the opposite ends of the adjustement spectrum.

I agree that if you extrapolate instead of the 30 lbs. difference at 5" /sec. we may see a 60 lbs. difference at 10" / sec. But look at the randomnes of the lines versus adjustement.

As to useable range. 5" / sec. is fast. Unless you are building a car for gravel roads anything after that does not matter. Yes, a pothole may feel stiffer - but that setting has no impact on performance.

Let me show you what and adjustable shock should be able to do:

<img src="http://www.startupracing.com/images/Suspension/RbAdj.jpg">

You've got what appears to be a twin tube rebound adjustable shock there. Probably a KONI or something similar.
It's not completely comparable to a monotube.

When you change the input, the curves will change dramatically. He's an example of a KONI shock at the speeds shown on the left.

<img src="http://pictureposter.audiworld.com/13830/dyno.jpg">

The 3-way <a href="http://penskeshocks.com/8760.htm">Penske 8760</a> we use on our race car is independently adjustable for low speed bump, high speed bump, and rebound. Once springs and sway bars are correct, low speed (less than 1"/sec) damping is adjusted to control load transfer and basic handling thru the various phases of a corner. High speed damping primarily determines how the car responds to rough track or corner exit alligators. Measurements up to 5"/sec are more than sufficient.

The <a href="http://www.neohio-scca.org/comp_clinic/hand_out_reprints/damper%20_2003_handout%20.pdf">Basic Damper Fundamentals</a> pdf was written by Dave Weitzenhof, one of the best drivers I know. <a href="http://www.ozebiz.com.au/racetech/theory/shocktune1.html">Shock Tuning</a> explains in detail how load transfer affects handling.

1. Steve Weiner, considered one of the most knowledgable p-car guys in the country, has found from testing that PSS9's (for p-cars) indeed have distinct settings:

http://forums.rennlist.com/rennforums/showpost.php?p=3442160&amp;postcount=12

2. Bilstein's curves (taken at 1.5 in/sec pk) show distinct settings:<ul><li><a href="http://www2.bilstein.de/en/produkte/wettbewerbsvergleich.php3#16">http://www2.bilstein.de/en/produkte/wettbewerbsvergleich.php3#16</a</li></ul>

993 PSS9s and Audi PSS9s could be very different. If you read his post carefully he states that #1 and #9 are different, the rest... well up to your interpretation.

I am getting 220 wired to my garage, then we will test at additional speeds. Why not - it will be free then.

Their chart shows m/s... .5 m/s is a BIG bump, mosty of us operate well below .5 m/s. If you look at .5 m/s and below, disregard red line - that is stock, there isn't that much difference. Also notice how they only show #1, #4 and #9...

Bilstein Adjustable DOES NOT EQUAL Ohlin or Penske adjustable. You are not buying world class here. I think that they may be better than some Konis and other street suspensions, but they are not discount Penskes/Ohlins.