Front Strut Bar Installation
Why
In terms of performance, strut bars stiffen the chassis by rigidly connecting the top of the strut towers together. This is important because it keeps the strut towers from flexing under heavy cornering loads.
In a stock car, the strut towers do not flex excessively because the springs are soft and the tires are not capable of creating high cornering forces. However, I have replaced the stock springs with Megan Racing springs,which are about three times stiffer than stock in the front and more than two times stiffer than stock in the rear. As a result, when you hit a bump or go into a corner, it is much more difficult to compress the springs. If the strut towers have no additional reinforcement, then the strut towers flex to absorb the bumps (since it is so difficult to compress the stiff springs).
Furthermore, I'll be using Falken RT615 tires during autocross competition, which provide much more grip than normal street tires. This will lead to more stress placed on the chassis of the car due to higher cornering forces.
In addition to providing better performance due to increased chassis rigidity, strut bars can also extend the life of the chassis. Using extremely stiff springs or adding significant power places extra stress on the chassis that it was not designed to handle. As a result, parts of the chassis can crack, and seams can separate. This is especially true if the car has a decent amount of rust on it (like mine). Therefore, strut bars should help extend the life of the car.
Option made a promotional film for Cusco that explicitly shows the performance and rigidity improvement achieved from using strut bars. In the first part of the video, a Nissan Silvia (S15) is lifted by a jack at the left front corner to show the amount of flex in the body when strut bars are not used. Also, the car is driven through a slalom with and without the bars, and suspension travel is compared. With the strut bar, the car experiences 6mm more suspension travel than without the bar. This shows that the suspension is absorbing the bumps and cornering forces more when the strut bar is installed. Watch the video on Option's website.
I specifically chose DC Sports strut bars because they are one-piece steel parts. This should be stiffer than conventional bars that have a bolt on each side to tighten.
Installation
For now, I've only installed the front strut bar. I'm still stripping the paint/rust from the trunk, so it's a mess back there. I'll install the rear bar once I've put the interior of the car back in.
- Remove the three 14mm nuts on each side that hold the top of the struts to the strut towers.
- Clean the top of the strut towers. Goo Gone cleaner followed by a 1:10 ratio mixture of Simple Green:Water scrubbed with a toothbrush helped get the grease and dirt off.
- Slide the front strut bar over the studs, and align the bar in the center if there's any free play. The holes on the strut bar are slotted to allow for easy fitment. On my car, the strut studs were close to the inside part of the slots on the bar, so there was no room to move the bar right or left.
- Finger tighten the three 14mm nuts on each strut tower.
- Tighten the nuts to 29-40 ft-lbs. as recommeded in the factory service manual.
Results
As far as fitment goes, I'm not completely satisfied. There's plenty of hood clearance, but the strut bar is touching the plastic fuel rail cover to the right of the valve cover (see picture). I'm not sure if it was there before, but after driving the car for a while with the strut bar installed, I noticed a small crack on the fuel rail cover under the bar. I don't think there's much to worry about though since it's just touching the cover. I'll keep an eye on it to make sure it doesn't cause any problems.
As for the performance in normal driving, I hear less creaking from the front of the car when going up a driveway diagonally or driving on a bumpy road. There's still a lot of creaking from the back though. Hopefully, the rear strut bar will reduce that when I install it.
I won't really be able to comment on true performance gains until the autocross season begins in March.