C Street Strut

[bill]

I'm driving a 2000 Boxster S in C Street currently.  Thinking of putting on Koni Sport or Bilstein B6 struts.  I have read and re-read the class rules and from what I read both those strut will keep me in C Street.  Also, from what I read I cannot do any modifications that would allow me to increase camber beyond what is currently on the vehicle.  Just want to check and ask if my interpretation of the rules are correct.  Thanks for any feedback.

[Morlandella]

Yes you are correct. You can change your shocks as you please so long as ride height remains stock. You are not allowed to modify your alignment capabilities beyond what the car already has. 

[Matt U]

Bill, sometimes there are little things written in the factory service manual that allow for smaller diameter bolts on the lower part of the strut. A quick Google search and it seems that the lower strut mount on yours is a ring style, so there’s no adjustment there. 
 

Regarding the rules, basically the lower spring perch to the wheel centerline on a strut can’t be anything different than O.E. So the Koni and Bilstein are the right choice. There is also a rule that droop travel needs to be 1” or less difference from the O.E. shocks. 
 

Just because I did the research on this a while back, I figured I should share. Now, Koni makes the Str.t (street pronunciation apparently), and the yellows. The Str.t is a non-adjustable version of the yellow at full soft. The yellow have a “rebound” adjuster only. I say “rebound” in quotes because there is what is called cross-talk in the yellow’s, so about 40-50% of what you add in rebound will also be added in compression. 
 

Now on to the Bilstein camp. There is the B6 and the B8 that are both viable options that are class legal. Now before you say that the B8’s are designed to work only with lowering springs, that’s not really the case. I talked with a few shops that rebuild them and they all agree that the B8 will work with stock springs. The biggest difference with the B8 is that the amount of droop is 1” less than the B6, which is legal, and the B8 is slightly stiffer. One big thing to note on the Bilstein’s is that they are mono-tube shocks, so they will flex less. The other thing that may influence your decision is that because the Bilstein’s are mono-tubes, the nitrogen pressure in the shocks actually acts as a bit of additional spring rate. I have heard about 10-15 lb/in in addition spring rate just due to the shock alone, for both the B6 and the B8. This can help a softly sprung car be a little bit better in the roll rate department. Lastly the Bilstein’s are non-adjustable, but there are a lot of shops that can re-valve them if you need it. 
 

I know there’s a lot to digest, but I figured I would put it out there. 

[jw1]

I'd contact Pro Parts USA and get the Koni Yellows.    I have used them on multiple cars and they are a good entry level shock that is adjustable.