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Old Sat, Jan-10-2009, 03:57:40 PM   #9
Join Date: Jun 2008
Posts: 464
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ahhh, the famous clunk right after or not long after an FCAB replacement haha..

been there done that

Here is something a lot of people don't know about our control arms:
the hex points on the lower control arms that slide into the FCAB sleeve vary in size. Yes, I'm talking about the OEM control arm and what i like to refer to as the FCAB "pivoting" (for lack of a better word I guess) point. And while the thickness of this pivoting point is very close to that of another random control arm's pivoting point, it is NOT as equal and precise in size as other components on the car. Go ahead, call TCKline, ground control, etc. and ask them about it.

That is why 50% of people experience some sort of issue with their FCABs at some point. Now, you may wonder why the stock FCABs are NEVER affected by this varying size of the pivots. That's because the stock FCABs are extremely tight and are able to be seated on the sleeve perfectly snug due to the fact that they are essentially made of rubber. Rubber stretches and so even with the variances in pivot sizes, OEM FCABs are able to provide a perfect fit. Of course all this at the expense of reduced steering response.

Aftermarket FCABs are typically urethane or some other material. Some have rubber-like components also, but they are typically reinforced by metal (e.g. Powerflex FCABs - also note that there were 2 versions of the Powerflex FCABs) or another material. Whatever the case, aftermarket FCABs are stiff and they are stiff for a reason. Because of this stiffness, they are able to tremendously improve your car's steering response. The downside is that because of this stiffness and "non-stretchiness" (like that of the OEM FCABs), it's much more difficult to have them seated properly.

When installing aftermarket FCABs, you will experience one of the three:
(1) they fit perfectly the first time you try to hammer them on (wow, this rarely happens), but they are seated very tight and snug.
(2) they appear to be too small. You try to hammer the sleeve of the FCAB onto the pivot and it's a no-go. You have to sand down the pivot point little by little until you can hammer them on. Like in #1, they end up being seated very tight and snug.
(3) they fit perfectly (almost with ease), but it seems too good to be true, so to speak. That's because the pivoting point is smaller than the typical (if there is such a thing ) pivoting point. In other words, it appears that the sleeve of the FCAB is bigger than it needs to be. But actually, it's the control arm pivot that is too small.

Honestly, #3 gives a lot of people trouble later down the road. Ask me how I know. I had this happen with my Ground Control urethane FCABs twice. They are MUCH stiffer than the Powerflex FCABs and they are superior in terms of steering response. This is not even up for debate, they ARE superior in that regard. However, they are also much more difficult to seat properly due to the fact that the bushing has no flexibility whatsoever. The Powerflex does.

that is why in terms of steering response,
GC FCAB > Powerflex FCAB

...but in terms of being more comfortable, noise-free, and clunk-free ,
Powerflex FCAB > GC FCAB

To me, it's a no-brainer. For street and semi-track applications, always go with Powerflex FCABs. For serious track/race setup, choose GC FCABs. In either case, the improvement over the stock FCABs will be noticeable and significant, to say the least.

Also, that's not to say that Powerflex FCABs will never give you trouble and will remain completely clunk free. Again, with the FCABs you are sort of rolling the dice because how well it is seated depends more on the pivot of the control arm rather than the FCAB itself. I've had my Powerflex FCABs for 1.5 years and they are 100% clunk-free. I've had GC FCABs prior to this and replaced them twice within 6 months. No matter what I did, I would develop a clunk after a while on the drivers side (another proof that not all pivot points are equal). I personally spoke with several individuals who experienced the same identical issues on either driver or passenger FCABs. Then again, there were those who did not.

Last edited by swaybar; Sat, Jan-10-2009 at 04:01:33 PM.
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