Very interesting discussion indeed!

I've never had my PSS9's dyno'd, so I'm not sure how much of an effect (if any) the adjuster has on low speed dampening (on the RX-8 version). Medium and high speed dampening definitely seems very good on my RX-8 PSS9's (as Shaikh noted with the 350Z version), as the ride quality I've observed on the street is quite exceptional (you typically hit medium & high speed shock speeds when you go over potholes and bumps on the street and 'rumble strips' on the track).

I have no plans to revalve my shocks at the current time. With the front spring rate change I made, they've been working extremely well. With this said, I'd suggest talking directly to Bilstein in Poway, CA and see what their capabilities are if you decide to get the PSS9's revalved (they revalve PSS9's for $125/shock iirc).

Good luck whatever you decide.

Not sure how they look on a shock dyno. But I know even 1 click will make a noticeable change in how the car handles.
If you are interested in a set, I will have a very lightly used set for sale very soon.

Why are you deciding to get rid of them for solo8? Going a different route. I wanted to try and save for the fcm single adj coilover but I'm not sure of the extent of my racing. I don't plan on competing so I'm unsure of what to do at the moment. Unless u accept payments and want to sEnd me on one coil at a time I don't think I'll have any mine for anything. Especially when I just spent some of my coil money on that gb for the gt200.

^He bought a shifter kart, so his RX8 has become his tow vehicle.

Nice. Those are scary fun.

Yes, bought a shifter kart. Nothing wrong with my PSS9s and nothing not to like about them.

Bump and Droop travel
 

Okay, now that my new springs have been installed for several months and I've completed all the necessary tweaks to my bump stops, ride heights and alignment, I wanted to get another estimate of what the droop and bump travel are for my PSS9's.

These calculations/measurements are obviously estimates and not meant to be precise. My ride heights F&R on level ground are 13.5" all around (center of hub to top of wheel arch). I put the car up on four jack stands and then took this measurement again to determine the droop travel F&R.

FRONT PSS9's
Total front shock travel (~5.5")
https://www.rx8club.com/attachment.p...1&d=1263478092

REAR PSS9's
Total rear shock travel (~6.5*")
https://www.rx8club.com/attachment.p...1&d=1263478092

*Note*: Rear shock travel is 6.5" and not 6.0" as I used in previous calculations (didn't measure to the plate)

From the PSS9 manual, these coilovers come with 40mm bump stops F&R -- which means that ~1.58" of each shock's total travel is taken up by the bump stop. However, I cut 4mm from each of my front bump stops (making them 36mm bump stops), so for the front only, ~1.42" of shock travel is taken up by the bump stop.

The rough measurements I got for F&R droop travel were as follows:

Front = 16.5" - 13.5" = 3.0" of droop travel
Rear = 17.0" - 13.5" = 3.5" of droop travel

I then used these measurements to calculate my bump travel F&R:

Front: 5.5" - (3.0" + 1.42") = 1.08" of bump travel
Rear: 6.5" - (3.5" + 1.58") = 1.42" of bump travel

The bump travel F&R seems reasonable, but the amount of droop travel is definitely impressive.

http://dac.smugmug.com/My-Autocross-...32_FarDD-L.jpg

So in a picture like the one above I'm probably just getting into my left front bump stop on corner entry. However, from reviewing mid-corner and corner exit photos, my car seems to be off of them.

I'm very keen to see how my set-up works on the grippy concrete at the Little Creek Amphibious base in 2 weeks when I attend the Virginia Autocross Championships.

How low are you compared to stock? Looks like about -1.5"? How did you choose the ride height?

Also, note that because of the motion ratio 1" of wheel movement is about .9" of shock movement.

So droop is probably more like (16.5-13.5)*.9 = 2.7" at the shock (3" at the wheel)

Making bump travel 1.38" at the shock or 1.38/.9 = 1.53" at the wheel.

(I'm not sure about the .9 motion ratio so if anyone knows the real number please speak up.)

Great post! Very good point re: motion ratios. I completely forgot about that and I need to research this some more...

Btw, I'd also estimate that my ride height is ~1.5" lower than stock.

To be honest, I ended up at my current ride height based on the input of other RX-8 STX competitors. I know some who have gone as low as 13.0-13.25" in the front and I know of others who have run ride heights in the neighborhood of 13.75". 13.5" seemed like a good starting point and as it turned out, I needed my car to be at least this low in order to get front camber of -2.5 deg on my stock a-arms.


Edit--I did find this page on FatCat's site: http://www.fatcatmotorsports.com/FRC...M_MSDS_RX8.htm
Shaikh mentions the following: **Assuming** Shaikh's MR's calculations are accurate for the RX-8, I get the following numbers:

FRONT
(16.5-13.5)*.82 = 2.46" of droop travel
=> Bump travel will therefore be 1.62" at the shock (~2" at the wheel)

REAR
(17.0-13.5)*.84 = 2.94" of droop travel
=> Bump travel will therefore be 1.98" at the shock (~2.36" at the wheel)


Edit #2--I came across this thread: https://www.rx8club.com/series-i-wheels-tires-brakes-suspension-55/motion-ratio-140446/
And then this post by TeamRX8:
Plugging in these MR's, gives me the following numbers:

FRONT
(16.5-13.5)*.752 = 2.256" of droop travel
=> Bump travel will therefore be 1.824" at the shock (~2.43" at the wheel)

REAR
(17.0-13.5)*.855 = 2.99" of droop travel
=> Bump travel will therefore be 1.93" at the shock (~2.26" at the wheel)

Very interesting! I guess you'll have to measure to find out the MRs for sure. I thought manufacturers usually built in more bump travel in the rear, that way the fronts hit the bumpstops first which makes the car understeer at the limit. Have you noticed any snap oversteer that would indicate you are hitting the rear bumpstops before the fronts? Or are you off the bumpstops all the time?

By the way, are the "helper" springs fully compressed when the car is stationary?

Another random note is that when you want to find the wheel rate (the spring rate as "seen by the wheel") you multiply the spring rate by the motion ratio squared so wheel rates would be:

Front = 340 * (.75)^2 = 191 lbs/in at the wheel
Rear = 260 * (.85)^2 = 188 lbs/in at the wheel

For the stock PSS9 setup, so really the wheel rates are almost the same assuming Team's MRs are correct. When you take into account the slight front weight bias the bounce frequencies are probably identical front to rear, a very nice setup indeed.

I get a front frequency of = sqrt((191 * (lbf / in)) / (800 * pounds)) / (2 * pi) = 1.52804203 hertz
And for the rear = sqrt((188 * (lbf / in)) / (750 * pounds)) / (2 * pi) = 1.56571209 hertz

So a slightly higher rear frequency than the front, which is usually recommended. Also you are right in the sweet spot of 1.5-1.6 recommended for streetable performance! Way to go Bilstein!

What setting would the R3's Bilsteins stiffness be on the PSS9s? Roughly.

I'm not sure what the R3 spring rates are. Also, I believe the R3 shocks are Bilsteins but not the springs, also they are probably more comparable to Bilstein HD shocks, the internals of the PSS9 are different. Anyways, if you can find the spring rates for the R3 you can plug them into those formulas above (if you copy that forumla into google and hit search it will do the calculation for you!).

I'm pretty sure I don't hit my rear bump stops at all. The thing about the Bilstein design is that the rear coilovers use progressive rate springs. So as the spring compresses, the effective spring rate increases.
Yes. I actually checked that today when I was swapping to my STX wheels & tires.
Thanks. I'd have to agree that Bilstein seems to have engineered quite a respectable coilover system. I'm just trying to find ways to develop it into an even better system for autocross.

Bump.

I'm still in the process of fine tuning the handling of my car through shock adjustments, swaybar settings, alignment settings and tire pressures. Since my last post, I've done events on grippy concrete and asphalt and the car continues to handle extremely well with no glaring deficiencies/vices from these coilovers.

Concrete:
https://farm5.static.flickr.com/4138...bb84b3fe_b.jpg

Asphalt:
https://farm5.static.flickr.com/4085...a2ffdea7_b.jpg

great photos and info..

va plate in the front i am sorry! sucks.. :lol:

beers :beer:

^ Yeah, I won't lie...it does suck. But I do take it off for big autocross events (National Tours, Nationals, etc)

The MRs were given to me by Koni following their having clydes car in their shop for developing the RX-8 fitment. IMO several points of data are incorrect in the FatCat spreadsheet. It's still a good resource.

i hate having to keep my front plate on as well... if i take it off i get parking tickets on my steet... screw LA...

Really nice pics though!

Any Before and after pics. To compare the drop?

These are the best I could find:

Stock
Attachment 252547

PSS9's
https://farm5.static.flickr.com/4011...927e50edc0.jpg

https://farm5.static.flickr.com/4093...612ac613da.jpg

https://farm5.static.flickr.com/4134...3da05b36c6.jpg


Couple things to note:

1) In the PSS9 pics, my wheels are 17" in diameter. Also, the outside diameter of my tires on the 17's is 1" less than stock (25.0" vs 26.0").

2) The PSS9's allow you to adjust the ride height at each corner. I can lower my car another 1/4-1/2" or raise it another 1" or so from where my ride heights are currently.

3) Overall, I'd say my car is ~1.5" lower than stock as it currently sits.

^^^Awesome thanx.

I just finished reading all 18 pages :score:

Such great info'' espcially from you chiketkd and Solo8.

I'm definitely DEFINITELY purchasing these coilovers. They seem to fit my needs perfectly.:ylsuper:

They really are great. This thread helped me pick the PSS9s and they're quite the upgrade from stock. You can turn them all the way down to 1 for traveling long distances and crank them back up when you're ready to shred the asphalt. My slight-OCD-ness absolutely loves them because I can keep fiddling with the dials to find the ride quality I want.

Also, they're height adjustable, the usefulness you'll properly grasp when you realize you've dropped your car something awful and want it raised an inch or so back towards stock.

If I get the chance, I'll perhaps post a few pics so you can see the current ride height (sig pic is outdated).

FWIW, on the PSS9 kit the setting of '1' is firmest and '9' is softest. :)

Glad you're loving yours!

Btw, I posted this video in the STX thread over in the Competition section, but I figured I'd post it here as well.

It gives a good exterior perspective of my car on course and you can see how the car is still easy to drive/predictable even through the bumpy parts of the lot. I was 1st in class, 2nd in PAX at this event:

http://www.youtube.com/watch?v=B1ntvDfHdpA

awesome video chiketkd!!!