Bilstein PSS family
12-06-2009, 12:38 AM
#21
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Design flaws of the PSS9 adjuster - changes ride, NOT handling!
Jim,
Interesting that you are taking your experience (which you are not presenting all the details of) and now telling people to not use us when there are now TWO 350Z owners that are very happy with our services. The difference is that they bought PSS and you had a PSS9 because you had to have adjustability, so you thought. I initially thought that was a good idea but came to find out Bilstein's adjuster is a piece of marketing junk.
You had the misfortune of being the first (and last) person we dealt with to experience the Bilstein's PSS9 adjuster mechanism. Based on your own comments, the adjuster did not allow you to change the car's dynamics (which is what low-speed does). The ride simply got rougher with stiffer settings. Our dynos plus a tear-down of the shocks made it clear why this was happening.
First, Bilstein's adjuster goes through 180 degrees (1/2 turn) from 'soft' to 'stiff.' Even Koni, who is not as highly regarded in terms of quality as Bilstein, uses an adjuster with 2-2.5 turns. What was Bilstein thinking?
Second, the Bilstein adjuster changes forces in the mid-speed region, which is where ride quality, NOT handling is affected. As the PSS9's **** goes toward stiff, before you start to notice any handling changes (region from 0-3 inch/sec, typically), the ride quality degrades (3+ inch/sec region). The graphs speak for themselves.
Why would they do this, we and others asked? My reasoning is that Bilstein did not want an average driver to get into a situation where the car would be unsafe, so they remind the drive (via a rougher ride) that the stiffer settings could make the car (gasp!) oversteer more than expected. They increase the bounciness without making the car any more fun to drive. That's how lawyers apparently have to think and I understand the logic from a mass market point of view. However, an informed group of enthusiasts (am I assuming too much?) deserves a better thought-out product.
I've included three graphs to make it clearer what we had to deal with with Bilstein's design to achieve an adjusting profile similar what I've seen in true low-speed bleed adjusters. The last graph shows our FCM Variant 2 adjustable shock vs Bilstein PSS9.
#1 This graph shows the front PSS9 from soft (setting 1) to nearly stiff (setting 8). There is virtually no change in the low-speed (no surprised based on road tests), but noticeable change in the mid and high speed. This means the adjuster is changing ride quality, not handling. I don't think anyone would buy a 'Professional Suspension System' expecting the **** to be a gimmick.
#2 As the **** is turned from 8 to 9, the setting suddenly jumps significantly so the **** is highly non-linear and the change is still largely in the mid-speed region (3+ inch/sec). You indicated this setting made the car undriveable on the street. For spirited driving or competition, this setting or one near it (if there was finer resolution) would be useful. But the change from '8' to '9' has no 8.1, 8.2, 8.3 etc. We put the **** in some intermediate positions to approximate what that setting might be like.
#3 Looking at the Bilstein PSS9 coilover from soft to stiff vs the FCM Variant 2 coilover, you see how the force changes most significantly in the low-speed region on ours. The Bilstein barely doubles the 2 inch/sec force, which is where a driver would wants the strongest control for fast transitions. There is less than 50% change at 1 inch/sec while our adjuster gives over 900% change from soft to stiff! THAT's a real low-speed adjuster, what any serious enthusiast would want!
When we opened up the shocks and found a preloaded 'bleed cup', it was apparent the fluid going through the shock first had to deflect the shim stack on the bleed cup before it would enter the oil chamber. This effectively negated the low-speed nature of the shock, like having a plugged cat on your car. The engine isn't breathing as well. The problem we had was that in removing this handicap, the 1/2 turn range made it impossible to valve the shock to use the adjuster to give a proper damping profile across the board. We had to fix the adjuster in one position then valve the shock around that bleed position. The full stiff position would definitely be very stiff, but there was only one position that would work for daily-driving. It still DID work very well, but there wasn't a fine-tunable range of adjustment as we wanted to give you. It simply isn't possible with their design.
The extreme sensitivity, non-linearity, and non-low-speed nature of the Bilstein adjuster makes it a poor choice for anyone who wants to adjust their G35/350Z's balance. Yes, there is some low-speed change, but there's a harsh penalty in ride quality once you turn the **** past soft. A well-designed low-speed adjuster will not worsen ride quality as it gives the driver a nicely controlled, wide range of adjustment. I designed ours custom adjusters to have a very wide useful range, even before seeing how bad the PSS9 mechanism is. In fact, our shocks have wider range than many Penskes I've seen. We provide 6 TURNS of adjustments from the full stiff position, to softer than your father's Cadillac. The typical user only needs to go about 3 turns from stiff for their street/wet setting, and can stiffen as needed for track/competition.
I hope this clarifies more of why we could not achieve a 100% solution while retaining the Bilstein adjuster. Bilstein was able to revalve their product to give the new owner a result they are happy with. That's good - however, the basic character of this adjuster hasn't changed. It still has 1/2 turn and a very non-linear nature.
Regarding money, we spent well over 15 hours servicing your shocks. That's a cost to us of over $1500, not to mention the volume of phone calls and emails. We both invested time and money. I understand your disappointment in having an adjuster that did not perform as you wished. You didn't know what you had bought and we didn't know what you had until we'd already opened up the shock. Now we're both wiser for it. I can't count the thousands of dollars I've spent on products where I received 1/10th the customer support I offered you. But I was not willing to provide you a refund for a service that ultimately DID provide you a car that was a blast to drive.
I'm glad Derek and others are choosing to work with us and I'm glad the new owner is happy. I think it's fair to let other G35 and 350Z owners decide what route they wish to take. I like to present facts more than opinions. I spent the time and stayed up late on a Saturday night to provide a more thorough explanation of why we did what we did.
Our history:
We have OVER 100 totally satisfied Miata customers, from street to track. Multiple wins in endurance road racing (SCCA and NASA), TWO Solo National championships and over 7 Solo National Tour wins. We supply our shock mount kit to SCCA and NASA for the Spec Miata series. Now, we also have two happy 350Z owners. There are recent requests from companies who want us to build shocks for F-Body and Hyundai markets. I am confident we are doing the right things and making the best decisions we can.
In the meanwhile, I also wait for Derek's full review. He offered me the pleasure of driving his car which reminded me a lot of Jim's after our last revalve. I'd have been happy daily-driving it, with a bit softer spring rates.
Shaikh
Interesting that you are taking your experience (which you are not presenting all the details of) and now telling people to not use us when there are now TWO 350Z owners that are very happy with our services. The difference is that they bought PSS and you had a PSS9 because you had to have adjustability, so you thought. I initially thought that was a good idea but came to find out Bilstein's adjuster is a piece of marketing junk.
You had the misfortune of being the first (and last) person we dealt with to experience the Bilstein's PSS9 adjuster mechanism. Based on your own comments, the adjuster did not allow you to change the car's dynamics (which is what low-speed does). The ride simply got rougher with stiffer settings. Our dynos plus a tear-down of the shocks made it clear why this was happening.
First, Bilstein's adjuster goes through 180 degrees (1/2 turn) from 'soft' to 'stiff.' Even Koni, who is not as highly regarded in terms of quality as Bilstein, uses an adjuster with 2-2.5 turns. What was Bilstein thinking?
Second, the Bilstein adjuster changes forces in the mid-speed region, which is where ride quality, NOT handling is affected. As the PSS9's **** goes toward stiff, before you start to notice any handling changes (region from 0-3 inch/sec, typically), the ride quality degrades (3+ inch/sec region). The graphs speak for themselves.
Why would they do this, we and others asked? My reasoning is that Bilstein did not want an average driver to get into a situation where the car would be unsafe, so they remind the drive (via a rougher ride) that the stiffer settings could make the car (gasp!) oversteer more than expected. They increase the bounciness without making the car any more fun to drive. That's how lawyers apparently have to think and I understand the logic from a mass market point of view. However, an informed group of enthusiasts (am I assuming too much?) deserves a better thought-out product.
I've included three graphs to make it clearer what we had to deal with with Bilstein's design to achieve an adjusting profile similar what I've seen in true low-speed bleed adjusters. The last graph shows our FCM Variant 2 adjustable shock vs Bilstein PSS9.
#1 This graph shows the front PSS9 from soft (setting 1) to nearly stiff (setting 8). There is virtually no change in the low-speed (no surprised based on road tests), but noticeable change in the mid and high speed. This means the adjuster is changing ride quality, not handling. I don't think anyone would buy a 'Professional Suspension System' expecting the **** to be a gimmick.
#2 As the **** is turned from 8 to 9, the setting suddenly jumps significantly so the **** is highly non-linear and the change is still largely in the mid-speed region (3+ inch/sec). You indicated this setting made the car undriveable on the street. For spirited driving or competition, this setting or one near it (if there was finer resolution) would be useful. But the change from '8' to '9' has no 8.1, 8.2, 8.3 etc. We put the **** in some intermediate positions to approximate what that setting might be like.
#3 Looking at the Bilstein PSS9 coilover from soft to stiff vs the FCM Variant 2 coilover, you see how the force changes most significantly in the low-speed region on ours. The Bilstein barely doubles the 2 inch/sec force, which is where a driver would wants the strongest control for fast transitions. There is less than 50% change at 1 inch/sec while our adjuster gives over 900% change from soft to stiff! THAT's a real low-speed adjuster, what any serious enthusiast would want!
When we opened up the shocks and found a preloaded 'bleed cup', it was apparent the fluid going through the shock first had to deflect the shim stack on the bleed cup before it would enter the oil chamber. This effectively negated the low-speed nature of the shock, like having a plugged cat on your car. The engine isn't breathing as well. The problem we had was that in removing this handicap, the 1/2 turn range made it impossible to valve the shock to use the adjuster to give a proper damping profile across the board. We had to fix the adjuster in one position then valve the shock around that bleed position. The full stiff position would definitely be very stiff, but there was only one position that would work for daily-driving. It still DID work very well, but there wasn't a fine-tunable range of adjustment as we wanted to give you. It simply isn't possible with their design.
The extreme sensitivity, non-linearity, and non-low-speed nature of the Bilstein adjuster makes it a poor choice for anyone who wants to adjust their G35/350Z's balance. Yes, there is some low-speed change, but there's a harsh penalty in ride quality once you turn the **** past soft. A well-designed low-speed adjuster will not worsen ride quality as it gives the driver a nicely controlled, wide range of adjustment. I designed ours custom adjusters to have a very wide useful range, even before seeing how bad the PSS9 mechanism is. In fact, our shocks have wider range than many Penskes I've seen. We provide 6 TURNS of adjustments from the full stiff position, to softer than your father's Cadillac. The typical user only needs to go about 3 turns from stiff for their street/wet setting, and can stiffen as needed for track/competition.
I hope this clarifies more of why we could not achieve a 100% solution while retaining the Bilstein adjuster. Bilstein was able to revalve their product to give the new owner a result they are happy with. That's good - however, the basic character of this adjuster hasn't changed. It still has 1/2 turn and a very non-linear nature.
Regarding money, we spent well over 15 hours servicing your shocks. That's a cost to us of over $1500, not to mention the volume of phone calls and emails. We both invested time and money. I understand your disappointment in having an adjuster that did not perform as you wished. You didn't know what you had bought and we didn't know what you had until we'd already opened up the shock. Now we're both wiser for it. I can't count the thousands of dollars I've spent on products where I received 1/10th the customer support I offered you. But I was not willing to provide you a refund for a service that ultimately DID provide you a car that was a blast to drive.
I'm glad Derek and others are choosing to work with us and I'm glad the new owner is happy. I think it's fair to let other G35 and 350Z owners decide what route they wish to take. I like to present facts more than opinions. I spent the time and stayed up late on a Saturday night to provide a more thorough explanation of why we did what we did.
Our history:
We have OVER 100 totally satisfied Miata customers, from street to track. Multiple wins in endurance road racing (SCCA and NASA), TWO Solo National championships and over 7 Solo National Tour wins. We supply our shock mount kit to SCCA and NASA for the Spec Miata series. Now, we also have two happy 350Z owners. There are recent requests from companies who want us to build shocks for F-Body and Hyundai markets. I am confident we are doing the right things and making the best decisions we can.
In the meanwhile, I also wait for Derek's full review. He offered me the pleasure of driving his car which reminded me a lot of Jim's after our last revalve. I'd have been happy daily-driving it, with a bit softer spring rates.
Shaikh
12-06-2009, 01:14 AM
#22
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Here is a graph of a 350Z rear Koni (blue curves), from soft to stiff, compared to the PSS9 for G35/350Z (in red). You can see how the Koni adjusts the low-speed (rebound) more than the Bilstein PSS9 does. The mid/high speed on the Koni increases because it uses a preloaded valve on the bleed instead of a needle, but the **** IS actually adjusting the low speed force so the driver can tell its doing something useful.
01-04-2010, 05:24 AM
#25
PSS, PSS9 and PSS10 all share spring spec and perch design so they all lower the same. Only difference is the shock.
The instructions allow you to remove the adjustment ring so the spring perch sits on the last threads. This allows for about a fingers width between my 35 series 18.275 tire and the fender. Plenty low enough for me, but not slammed like you can get with other setups.
The instructions allow you to remove the adjustment ring so the spring perch sits on the last threads. This allows for about a fingers width between my 35 series 18.275 tire and the fender. Plenty low enough for me, but not slammed like you can get with other setups.
01-04-2010, 09:18 AM
#26
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PSS, PSS9 and PSS10 all share spring spec and perch design so they all lower the same. Only difference is the shock.
The instructions allow you to remove the adjustment ring so the spring perch sits on the last threads. This allows for about a fingers width between my 35 series 18.275 tire and the fender. Plenty low enough for me, but not slammed like you can get with other setups.
The instructions allow you to remove the adjustment ring so the spring perch sits on the last threads. This allows for about a fingers width between my 35 series 18.275 tire and the fender. Plenty low enough for me, but not slammed like you can get with other setups.
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