fbfisher

So it turns out that Addisons Eibach springs are for a C4S. Addison Writes:

"I just talked to Eibach and here is what they told me. The springs for my C4S are part #7209.140 but they also have a different part #7208.140 for the C2 and C4 Cabs and Targas. According to the tech I spoke with, the spring rates are different but he could not give me specific numbers. They are the same size."

Will these work on my car?

fbfisher

Front | Rear

C2 PRO-KIT |1.3 in | 1 in | part # 7208.140
C4S PRO-KIT |1.5 in | 1.5 in | Part # 7209.140

From these specs, if I understand them correctly, the C4S kit lowers the car and additional 0.2 in the front and 0.5 in the rear. Still trying to find someone to tell me if this is a problem or not -

Eibach's site states: "Only simple linear springs have a spring rate. A sophisticated progressive Eibach Pro-Kit spring has a load/deflection characteristic. The special design parameters are only accessable through Eibach Desk-Tech Database to Eibach’s exclusive partners."

Given the assumption that they are the same size but different spring rates. I'm not clear what the implications of that are either.

Any help is most appreciated.

hdemas

I don't know if it will be a problem in your case. However, my brother used to work at a shop where in one case I remember him telling me about they were sent the wrong springs to install on a car--sent springs for a coupe where they were supposed to send springs for a cab. They called the supplier and were told not to use those springs and to wait for the correct ones to be sent. The reason they have different springs is because of different weights of the cars. Porsche is really picky about the springs they use, and I've heard that on some cars they use different springs even as a result of option level if there is a meaningful change in weight. As for aftermarket springs, it may work ok, especially given that they are stiffer than factory springs, but you risk having the ride height ending up too high or low. For example, your car may be lighter in the front than a C4, but heavier in the rear due to the cab mechanism, so the amount it actually ends up being lowered may be different, and worse yet it may not end up with the appropriate amount of front vs. rear drop, which would make the car not "sit" right.

My recommendation is that if Eibach makes different springs for the coupe and the cab, make sure you get the right ones. Eibach tests these things and there is a reason they sell different springs for the different cars. Considering how expensive the other things are that usually are involved with changing springs--shocks and, at the very least, alignment--it costs relatively little to get the right springs and so there really is no reason to be second-guessing the engineers at Eibach.

fbfisher

Good thoughts Harry. Thanks for the reply. I look forward to others more informed than myself chiming in on this.