Koni FSD vs Bilstein B4 for 05 X3

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Now that the X has gotten a new head, its time for suspension! Rear coils are broken, so deciding between shocks and struts. The B4 and Konis I can get at basically the same price, so looking for experiences with either. Id normally go with the B4, but the Konis are on sale bringing the price down by 150. Im also considering the B4s from the sport package X3 for a little more, but want to confirm the springs are correct. Thanks
 
FSD = WAY better ride quality
B4 = better longevity

Either should handle about the same as stock.

On any vehicle that I wasn't constantly pushing to its handling limits, I'd go FSD every time.
 
Try the FSD
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My personal experience with the FSD struts was not good on my 2010 Accord when I owned it. Struts rode great but made a clunking noise over bumps and Koni refunded my money under warranty. But, you might be okay because your application is a BMW.
 
FSDs worked great on my Mazdaspeed 3; I usually put Bilsteins on my BMWs(and Jeep) but I'd think the Konis would be a good choice for your application.
 
The B4's are Bilstein's economy dampers, meant for OE replacments, which are twin-tube dampers

The Koni FSD's are theoretically should be an upgrade to the Bilstein B4's, which uses a similar technology to Monroe Sensatrac, which adjusts dampening and rebound for the conditions of the road and driver inputs to the suspension, which FSD's are typically tuned softer for the comfort frequencies and adjusts to be firmer for sportier frequencies, though not quite as firm as the Koni Sports.
 
Going to go with the FSDs. Thanks for the help, will update with any issues that come up. The wife really uses this car most, and with the baby on the way trying to get everything ready. Also going to go with the heavy duty springs in the rear, in case I tow something small with the car.
 
I get the impression that a lot of people come to the FSD expecting that it'll be like any other "performance" damper, except with more of a comfort bias. IMO, what it's really for is improving ride quality with stock or stock-ish springs, without compromising handling.

If you want significantly better handling, you'll be disappointed with the FSD. I've also heard complaints that it makes the car feel weird at its handling limits. And it can't be expected to last longer than any other damper -- unlike Bilsteins, which are probably the longest-lasting dampers you can get.

But if you're happy with stock handling, don't push the limit, and want better ride quality, FSD is magic. I'm not sure anything on the market comes close. It's basically the perfect damper for... most people, really.
 
Definitely not looking to push the handling limits of the car with a baby seat in the back haha. I ordered the FSD, Im sure they'll be fine for the 8k a year max this car sees.
 
I missed that is was B4, OE replacement. B4 for the price of Koni's FSD is not a good deal at all, so definitely get the FSD!

Now, if it was a choice between B6 and FSD, then it's worth debating. But the FSD definitely > B4
 
The Konis were about 40% off, so they came down to the B4 price level. Hoping they get delivered today, I ordered new lower control arms, balljoints, and springs already, waiting on the Konis to start the install.
 
The Konis shafts were considerably larger than the OE Sachs in the rear, and slightly larger in the front. So far very impressed with build quality, says made in Holland which is reassuring.
 
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