H&R Performance sway bars

[germ]

Just got an email from ECS Tuning about those:

http://www.ecstuning.com/News/BMW_E8...012_2013_2014/

Apparently the same bars work on the vert as well. This is surprising to me, I had always seen bars for coupe only.

I've got two questions:
1. How hard would it be to install them on a vert? Is it a DIY job?
2. Which one is the better buy, just the front or both?

[brusk]

I'm curious on that. If you start with a car that already has a tendancy to understeer wouldn't adding a stiffer front sway bar make it even worse? I would think you'd get better results from wider front rubber and M3 control arms.

[128Convertibleguy]

Originally Posted by brusk

If you start with a car that already has a tendancy to understeer wouldn't adding a stiffer front sway bar make it even worse?

On a race car with double a-arm suspension front and rear, it would. On a car with MacPherson struts up front, not so much.

The sway bar transfers weight to the outside front wheel. Which increases understeer. But it also greatly improves wheel camber under hard cornering. Which decreases understeer. Which wins? Who knows? It depends on a lot of things. But reports here on just making the front bar bigger at least indicates increased understeer is not a problem if you change only the front.

Sway bars are extremely tricky. The front and the rear do very different things, especially on a car with MacPherson struts on the front. The front bar and the springs provide the vast majority of the roll control. The rear bar is largely for tuning the handling balance. It generally provides about 5% of the amount of roll control as the front, and only a couple of percent of the total roll control.

People (not just BMW guys) muck about with sway bars a lot without understanding exactly what they do and how they do it. Not the best idea. That also means any advice you get here may be questionable. Including my post. <grin>

[3002 tii]

There's a difference as to what feels better and what's faster. And yes, the MacPherson suspension has a weird camber curve which is why our cars respond better to thicker front sways. With that said, I've yet to drive my 1-er on track but I did change to the E93 M3 fsb and the car exhibited noticeably less roll. Great for daily driving, can't tell you though how it is on track.