I bought the STi strut bar a while back, and finally got around to installing it. I liked this strut bar mostly because of the clean design, but also was intrigued by the "flexible" design.
Contrary to popular belief, strut bars are meant to deflect/transfer loads from one strut tower to another to by tying them together but can be of virtually any design. Many OEM bars are cheaper hollow steel bars, while aftermarket bars often end up being a more intricate aluminum design (or prettier steel design).
After getting the STi bar, I wanted to look at how it was designed, so I pushed the STi rubber center cover to reveal the ball joint design:
From what I can tell, it's just a simple ball joint socket with two rubber covers over it. The package and instructions specifically state to not put load on this joint past a certain angle (when handling the bar), and I can see why; if you were to bend the bar more than ~45 degrees or so, it will pop the ball joint out of the socket.
Having said that, when pushing the ends together there's absolutely zero play. After seeing this design, now I understand why it is "flexible".
Under hard cornering, the bar acts as a solid piece and any deflection from one strut tower is transferred to the other. However, when driving in a straight line the bar allows one side of the car to "sag" or "go upwards" depending on the road condition. This is hard to describe but I hope someone (or STi themselves) can make an animation showing how this works.
Anyhow, install instructions (for those wanting to buy):
Tools needed:
- 12mm deep socket (or wrench)
- 5mm hex tool
- Long ruler/leveler
Time: approx. 15-20 minutes
Start by taking off the 12mm strut tower nuts.
Next, put strut tower bar onto shock towers, over the strut studs.
Tighten the 12mm strut tower nuts.
In this picture, you can clearly see the deflection the bar has shipped from the factory.
(no picture for this step but it's self-explanatory)
Use a 5mm hex tool to loosen the hex bolt on the ends of the strut bar from the end plates. Using the leveler (or some type of string/flat edge as a guide), move the bar so that it is level with the measuring edge. Tighten the 5mm hex bolt on one side, then move to the other side.
After you are done with this step, the leveler should look approximately like this:
Lastly: if you moved the rubber cover (or need to adjust it), there are white marks on both sides of the cover (and a corresponding white mark on the strut tower bar). Line these up on both sides to center properly.
Installation finished, go out and test drive!
-alex