Wednesday, February 9, 2011

Out with the squish!

Removing stock steering rack bushings
We replaced several factory squishy rubber suspension bits on our STI with firmer polyurethane versions from Whiteline.  On the menu this week were the rear differential mount inserts, front lower control arm bushings, the Whiteline Anti-Lift Kit, and the a set of steering rack bushings.  The idea of all these parts is to take out slop and squish from the system, resulting in more precise location of the suspension components so they can do their job more directly and without deflection.  The factory rubber stuff is soft and comfortable, but as I've complained about in early blog posts, the 2008+ STI feels a lot more vague in its steering feel than previous-generation cars.  I wanted some of that feel back.

 Note that the 2011 STI did get revised, slightly firmer rubber bushings at the front and rear control arms. These Whiteline parts will be firmer still, but the difference from stock on the 2011+ cars will not be as dramatic as on the 2008-10 cars.

Pointing to the stock rear diff carrier bushings
Our shop guys report that installing all these parts was very easy.  The steering rack bushings come with a cylindrical tool that makes pulling out the old bushings very simple.  The rear diff bushing inserts just push into the voids in the existing rubber bushings -- we spritz the rubber with glass cleaner to provide a bit of lubrication.  The two sets of front control arm bushings (the Anti-Lift Kit goes on the back of the control arms, and the control arm bushing set goes on the front) install easily, too.

Once the car was back on the ground, I took it out on the road to see if I could tell the difference.  The effect on the steering was immediate -- between the control arm bushings and the steering rack bushings, it feels like the steering from a different car.  There's much more immediacy in the reactions of the front end.  Twitch the wheel, and the nose of the car twitches.  Go over a ripple in the pavement, and you can feel it in the steering wheel.  I love the increase in precision -- I feel like I can place the nose of the car very exactly in a corner.

Pressing in the Whiteline rear diff bushing inserts
The rear diff bushings were not as easy to feel at the beginning.  Once I started driving the car hard, though, I could tell things were firmer.  There is less "bounce" from the rear under hard one-two gear shifts, and on-off throttle transitions produce less wiggling of the rear end of the car.  It's hard to describe this, because I didn't really notice it before, I just perceive the lack of it.  Getting on and off the gas when the car is loaded up in a corner, it seems to stay planted better than it used to.

I can't say there's no effect on comfort from these modifications.  The increased feel in the front end is also accompanied by more small bumps and impacts transmitted into the car.  The stiffer diff mounting is noticeable when the car goes over expansion strips or other quick, small impacts, and in the form of some additional drivetrain vibration and noise in the rear of the car.  (You probably won't notice this from the driver's seat, but rear seat passengers might.)  The car isn't uncomfortable to me at all, but it's firmer and not as plush-riding as the OEM bushings were.

Overall I'm quite happy with the changes.  The steering feel, in particular, is worlds better than it was before.  The whole car just feels more secure and planted because of the more direct connection to the road.