Okay, so I've had these on for about 300 miles or so...my impressions thus far but of course this is all very subjective.
The car is definitely more solid. As a matter of fact my wife just drove the car tonight and she said "I can't believe how tight the steering is now, it makes my car feel so sloppy". She has an FX but up until a few months ago drove a G37S. This was also the first time she drove the car since it got M3 arms, wheels and tires, additional camber (-1.5x4), and the rear bushings. She's right, it's pretty tight and the steering is a tad heavy but solid and great feedback. The car definitely feels more connected. In an earlier post I spoke of a section of road that I drive that had the backend bouncing up and down and rocking a bit. The rocking is still there due to the undulations in the road surface, but now it's more like the whole car is rocking. Shocks and struts will hopefully help with that. The back end bouncy feeling is gone.
If I flick the wheel as if I were avoiding a pot hole and flick it back, the car stabalizes pretty quick and I no longer feel like the front and rear settle at 2 different rates.
The corner I spoke of, I've nailed it a couple times pretty hard now, I still feel like I get launched a bit but again don't feel like the back starts doing the same sort of ballet it did before, it's a nasty approach to a corner. All things considered the car does pretty well. Again, hoping coilovers help with that.
Accellerations are definitely improved...no doubt about that. I don't feel near the dancing around that I did before the upgrade. Still get wheel spin of course, but only a slight wiggle out of the rear end.
Road noise and vibration...I've really tried to pay attention to this...it's sooo subjective. Is it increased, maybe slightly, I wouldn't consider my car a luxury ride in any way. With everything I've done, it's a much less clunky feeling, so I feel quite a bit but it's a sports car...I want to feel what's going on. It definitely handles the big stuff better now, so in that respect I'd say it's actually improved as far as vibration. Small stuff like rough road surfaces, it may be slightly worse. But I also run 36F/38R PSI, this could certainly contribute to that.
Understeer, I'm undecided on this one, so many variables (temps, surface...)...sometimes I think it has a tad bit more, others not at all. It's really hard when just driving on the street. Overall my car doesn't have much understeer, so if it contributed to it, it's certainly not much. I will literally come up to a 90 degree corner very hot and just throw the car in to it...no complaints (except from my passengers...lol). The backend is predictable and while I can certainly get it to oversteer post apex, it's a conscious decision and very predicatable.
Overall, I'm very happy with the upgrade, if I had known what I know now, I would have done it much earlier. So many stories of the installation costs and how you have to drop the rear end is a bit intimidating. If you're a DIYer, this is not hard, it really sounds much more intimidating than it is to actually do it. Pressing M3 bushings in "might" be a bit more tricky...I really wouldn't think so though. Lube em up and use the same trick I used to remove the old bushings (minus the heat) and let gravity and the jack do their thing. Work smarter...not harder
