I'd like to stiffen my ride (2006 330Ci ZHP, 6m) before next year's track season. Here's what BMW has to say about its performance control arm package: "With a tighter, sportier feeling, the inclusion of a BMW Performance control arm with stiffer bushings gives your 3 Series an almost instinctual feel for the road. With adjusted spring rates and bushings, roll is drastically reduced, creating cat-like quickness, increased responsiveness, and stunning agility. Flexing with the motion of your vehicle around even the tightest curves, a BMW Performance control arm means athletic handling, faster turn-ins, and a totally immediate and much more intense reaction to the tarmac. It delivers a perfect compromise between racing car performance and driving comfort." Ya, put me down for some of that. Reduced roll and "cat-like" quickness. But since I don't really understand how a control arm does all that I'm wondering who among you has replaced control arms and what the outcome has been. Conceptually I can see how struts, springs and/or a strut brace stiffens suspension. Control arms? Not so much.