I began to look into Bilstein PSS9 coilovers. I also checked a BMW forum, and read some independent opinions from Porsche owners, all seem to really like the PSS9s.

The PSS9 are monotube, 9 way single adjustables. For the RX-8 they are retailing around $1300 from a few vendors that responded to my inquiry.

What was interesting to me, is that if you look at the spring rates of the factory 6spd RX-8, they are:

155 Front
112 Rear

HKS RS Coilovers:
392 Front
280 Rear

Tein Flex:
503 Front
392 Rear

Many of the other available coilovers I've looked into are the same in that they maintain much stiffer springs in the front as compared to the rear. I assume Mazda has done this to prevent dive under hard braking, and to allow weight to be transferred to the rear under acceleration.

Bilstein's PSS9 rates, however are:

370 Front
375-445 Progressive Rear


I'm a bit confused as to why they have done this. Does this make sense to anyone else why Bilstein would have changed the spring bias from front to rear?

 

Most real-deal Porsche track racers will tell you the PSS9s are a great street setup but to mild for track. So depends on what you want. As far as your rear bias question, most RWD cars have a softer rear to slide (controllably) around. Too stiff and it'll swing (uncontrollably).

 

the progressive part makes it a little tricky... but i do looove my bilstein shocks on my M

 

That's interesting, I definitely don't want snap oversteer, but rather a progressive predictable loss of grip.

I was also confused by the linear rate in the front and progressive in the rear. Or maybe I just heard them wrong. Either way, I wasn't ready to go out and buy these tomorrow, and the more I think about them the more I lose interest and go back to thinking about HKS.

 

I'm also considering the PSS9's. Where did you find data on the spring rates? I couldn't find anything on the Bilstein web site.

 

ahh......... if you really want performance go with KW Variant 3 coilovers.

The top off the line for racers.

It will cost you big bucks.

 

you mean wannabe racers ... real racers use Koni 28 series, Moton, Penske, etc.

but back on topic, Speedsource uses 800# front & rear on their GrandAm cars

I don't know how they do it either I have 600# front, 325# rear, RB front swaybar and tiny OE auto-trans rear swaybar and my car was so spin happy at the National Championships last month that I couldn't do anything with it. We even put 800# front springs in and took the rear bar off and it still was too loose ...

 

I got those numbers directly from Bilstein over the phone.

As a side note, I didn't get these, I got the Tein Flex instead. My car is a daily driver, basically, and does see a few HPDE sessions a year. So they're more than adequate for my purposes.

 

I think that the stiffer setting on the front has to do with the weight of the front of the car vs the rear. Maybe? On my 911 and my GT3 my settings were the opposite since most of the weight of the car was on the rear. The RX-8 is more balanced but a little front-biased (as shown in a recent weighing session on the track).

 

I don't have a problem with the KW's.

Their 575 front with progressive rear