Since posting about my Ohlins suspension, I have received numerous PMs and emails asking me for more detailed thoughts about the PSS9s I ran for road and track previously. I think it prudent to add this quick post summarizing my thoughts about the PSS9.
I have driven on PSS9s on the track and street for the better part of 3 years, so I am very familiar with them. Let me take a moment to explain how the adjuster works on the PSS9. Have a look at this scale:
1..........2345678..........9
A setting of 1 is full hard. It is so hard, it will rattle your teeth out of your head as you skip off the track, which makes it useless. A setting of 9 is full soft. It is so soft, it is like driving a '59 Cadillac. Unless you like bouncy-floaty, it is also useless. That leaves the settings bunched in the middle. There really isn't much difference between a setting of 2 and 8, as the adjuster only turns 180 degrees, and most of that travel is between 1 - 2 and 8 - 9. At first, you will play around in that area trying to find what you like best. Eventually, you will realize that 5 is best for most conditions, and you will set it there and forget it (or wish you had your $500 back).
In my testing, I found a setting of 5 front and rear to provide a sporty feel on the street without being harsh or showing signs of weirdness that some of the other settings induce. On the track, I found a setting of 5 front and rear to be the best at keeping the car planted in most situations. Settings lower than 5 exhibited problems with compression over bumps and curbs, and higher settings exhibited problems with rebound, such as wheel hop under braking. Changing settings was rarely predictable and proved frustrating on many occasions. After experimenting with different settings over about 6 track days, I decided to just leave them on 5 all around, treat them as non-adjustable, and just drive to the available grip levels.
There is also the issue of what the adjuster is actually adjusting. I call it a "comfort" control, because it is not actually adjusting full spectrum rebound. It adjusts some combination of compression and high frequency rebound, and those are not always compatible in each setting. Some settings are just plain weird. High frequency rebound speaks to comfort, but low frequency rebound speaks to performance, and LF does not seem to change--except at the extremes of adjustment (and not in good ways).
The PSS10 has a much better design, but it is not available for our cars, unfortunately.
If I were buying Bilstein again, I would buy the non-adjustable PSS and save the $500 and months of frustration. Really, PSS9s set on 5 are very good street coilovers, and are also quite competent on the track. The non-adjustable PSS version should yield similar performance at a lower cost and with less frustration. I have not run the PSS myself, but I have spoken to the tech folks at Bilstein, and they tell me that, even though the spring rates are slightly different (370/240 PSS vs 340/240 PSS9), they are valved to those rates as if a PSS9 set on 5.
One last thought. Both PSS9 and PSS coilovers maintain a bump frequency that will bias a typical RX-8 from slight understeer toward slight oversteer with the factory sway bar ratio.
I have driven on PSS9s on the track and street for the better part of 3 years, so I am very familiar with them. Let me take a moment to explain how the adjuster works on the PSS9. Have a look at this scale:
1..........2345678..........9
A setting of 1 is full hard. It is so hard, it will rattle your teeth out of your head as you skip off the track, which makes it useless. A setting of 9 is full soft. It is so soft, it is like driving a '59 Cadillac. Unless you like bouncy-floaty, it is also useless. That leaves the settings bunched in the middle. There really isn't much difference between a setting of 2 and 8, as the adjuster only turns 180 degrees, and most of that travel is between 1 - 2 and 8 - 9. At first, you will play around in that area trying to find what you like best. Eventually, you will realize that 5 is best for most conditions, and you will set it there and forget it (or wish you had your $500 back).
In my testing, I found a setting of 5 front and rear to provide a sporty feel on the street without being harsh or showing signs of weirdness that some of the other settings induce. On the track, I found a setting of 5 front and rear to be the best at keeping the car planted in most situations. Settings lower than 5 exhibited problems with compression over bumps and curbs, and higher settings exhibited problems with rebound, such as wheel hop under braking. Changing settings was rarely predictable and proved frustrating on many occasions. After experimenting with different settings over about 6 track days, I decided to just leave them on 5 all around, treat them as non-adjustable, and just drive to the available grip levels.
There is also the issue of what the adjuster is actually adjusting. I call it a "comfort" control, because it is not actually adjusting full spectrum rebound. It adjusts some combination of compression and high frequency rebound, and those are not always compatible in each setting. Some settings are just plain weird. High frequency rebound speaks to comfort, but low frequency rebound speaks to performance, and LF does not seem to change--except at the extremes of adjustment (and not in good ways).
The PSS10 has a much better design, but it is not available for our cars, unfortunately.
If I were buying Bilstein again, I would buy the non-adjustable PSS and save the $500 and months of frustration. Really, PSS9s set on 5 are very good street coilovers, and are also quite competent on the track. The non-adjustable PSS version should yield similar performance at a lower cost and with less frustration. I have not run the PSS myself, but I have spoken to the tech folks at Bilstein, and they tell me that, even though the spring rates are slightly different (370/240 PSS vs 340/240 PSS9), they are valved to those rates as if a PSS9 set on 5.
One last thought. Both PSS9 and PSS coilovers maintain a bump frequency that will bias a typical RX-8 from slight understeer toward slight oversteer with the factory sway bar ratio.
A Few Words about Bilstein PSS9 Coilovers
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