I installed the Eibach kit on my '04 3.0 two years ago. I already had the 20" setup on it. The sport package 3.0 X5 was much more stiff after the upgrade and tracked more directly in highway transitions. Turn in was quick and body roll through the turn was significantly lower. The last thing I noticed was the added response I received from the X Drive front wheels. In pretty much any situation where I wanted to add throttle in a turn, I was able to do so sooner in the turn and with greater response from the driven front wheels than before. It makes sense- the vehicle is flatter, the wheels are more planted, the traction is better. But the application of it was surprising nonetheless.

I liked the setup so much that I moved the sways over to my 2004 X5 4.8is when I bought it last year (almost one year ago). I replaced the 3.0's sways with the ones from the 4.8is (same size for SPP 3.0's/4.4's). I drove the 3.0 to the shop with Eibach and back home without. I was surprised at how comfortable and responsive the 3.0 was with stock sways. It still provides a better balance than anything else its size. It felt much less aggressive, but still very capable.

On the 4.8is, the sways did not make such a difference. Or if they have, I just have yet to really feel it. One of the key differences in my two X5's was that the 3.0 was early production with the smaller sunroof. That means less weight up top to reel in with the 3.0. It's why *I* think the thing was so much more responsive than the 4.8is with all the glass. I love that smaller roof. I often see my next door neighbor tooling around in that old X5 and wonder if they've completely ground McDonalds fries into the seats. Could it be rescued?

Adding to the differences may also be the 4.8is' softer air suspension and drive by wire steering. The thing feels less connected to the road by design, so it would follow that the sways would improve, but not quite gain the same feel as they did on the 3.0.

With the Eibachs on the 4.8is, it still has all the grunt and it still grabs better out of a nice turn. Highway transitions are not as soft, and roll is reduced. But only so much can be done to challenge the affects of simple physics.

All in all, a nice upgrade for ~$500 in parts. The install is a killer, though unless you know some mechanics' tricks that I do not know. The way I looked at it, swapping the kit saved me about $400 after labor over just buying a new one for the 4.8is. It was worth it, and I like the results on both cars.

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