[Fireflyer239]

From what I've gathered, the Bilstein HD's and Koni FSD's are intended for use with stock- or near stock height springs, going about as low as say, Eibach Pro-Kits would take us. Bilstein Sports are, as Dackelone mentions, valved the same as the HD's but intended for use with lower springs (Eibach Sportlines, H&R's etc) and I have verified this with a call to Bilstein. They recommended using the HD's with the BMWP coils as opposed to the Sports due to the minor (10mm) drop I will see with these springs. Even the Bilstein rep admitted the HD designation can be misleading. He reminded me that as enthusiasts, we want ANY sport damper we choose to be "heavy duty", which I think is a great point. Would any of us buy a shock labeled "light duty"? He went on to remind me that the HD's intended for BMW's have valving appropriate for a BMW's intended use, and the HD's intended for a Chevy pickup will have valving appropriate for that vehicle's intended purpose.

Interestingly, Koni's website states that their Yellows are for use with lowering springs, but I think many folks also use them effectively with stock ride height (at least with a sport package-type stock ride height).

I think they are all good quality dampers. As pnosker states, the FSD's do have a reputation for delivering both comfort and performance, and for me it really came down to these or the Bilstein HD's. I ultimately went with the HD's for the following reasons:

1) Although this is my DD, I am mostly in the car alone and use another vehicle when carrying clients. I do not mind a firm ride and don't anticipate it will be excessively harsh. I have decided I'm willing to trade the increased comfort I'd get with the FSD's in return for very sharp response and more road feel with the HD's. I like to feel the little pebbles I'm running over.

2) The BMWP springs represent a fairly mild upgrade in spring rate, and the Michelin Pilot Super Sports have been praised for their comfortable ride, so I'm banking on the combination of these springs and tires to work with the HD's in delivering a decent ride.

3) It seems Bilstein's mono-tube design offers outstanding long term performance and reliability. I could find almost no negative comments regarding these dampers, and trust that the Bilstein engineers have selected a valving which I will find ideal. It's just me, but I don't really want adjustability - I want to install them and forget them. I was told these dampers have been revalved in recent years to be slightly more forgiving.

As mentioned, I've already done the Hotchkis front ASB (my car has the Sport Package so I won't need the rear ASB), so did not want to purchase the whole BMWP suspension kit. While I am sure the dampers provided with the kit are of better quality than stock, the fact that the stock dampers have gone floppy after 30K miles has left me with a bad taste for BMW branded dampers, regardless of who makes them. I fully believe the Bilstein HD's will be a perfect match for the BMWP springs.

I value the input from fellow members here, and look forward to reporting on the results upon install. I regret not having the time to do this work myself, as I've always worked on my own vehicles, but such is life at this time!