Initial Impression-- Koni FSD Dampers On an E91
Ordered them last week, installed them today and just got back from the 10 mile test drive. Of all the things said about the FSDs, the two that come most to mind are “there is a very noticeable improvement in comfort and handling” and “these are the dampers that should have been on this car when it left the factory.”
As many of you already know, Koni FSD dampers are unique in that they claim to be designed to have a two tier damping action. At rapid weight transfer, such as cornering, accelerating or stopping, the car stays level, not swaying or diving as much as OE dampers. At second damping action point, sudden bumps and deformities in the road surface are absorbed and smoothed out. These dampers are sold as a kit, which includes two front struts and two rear shocks. You can use your OE springs on the struts, purchase aftermarket springs, or buy a different kit from Koni that includes matched Eibach springs. I went with the regular FSD kit, i.e., I am using my OE springs with the FSD front struts.
I have been thinking of getting some Koni FSD dampers since I got my E91. Now that it has 50k miles on it I didn't want to put it off any longer. When I got serious about it, I started talking to car people and checking various forums online. Real life people generally spoke highly of FSDs. In the forums, most reviews were positive, but there were some incidences of premature leaking or outright failure.
One name came up in a post in 2007 and then again three or four years later. I paid particular attention to this guy’s posts because he had installed Koni FSD dampers on a touring and he owned them over a period of time. In fact, Highland Pete was the first to fit Koni FSD dampers to an E91 in the UK. Five years and 53 thousand miles later he told me he compares the ride on his touring to that of a Mercedes C-class sport with their version of the mechanical selective damper, i.e., nice and smooth with decent handling. This was a very persuasive endorsement.
Next step was to locate a vendor. There was pretty much just a generic BMW 328i fitment. But I knew that the OE E91 struts have a different part number than the E90 struts (although I don't know why) so I wanted to double check on the fitment. Koni's North American website only lists the 2100-4036 as fitting the E90 and E92, so just to be certain I contacted Koni tech or customer support. Their response: "These should work on your E91."
In the meantime, it seems these particular dampers were on nationwide backorder, no supplies expected until sometime in July. Two bimmerfest board sponsors basically said there were none to be had, give it up. One went so far as to add: "Koni does not list or approve this kit for any wagon models, so this would be a non returnable sale, 'order at your own risk' situation."
Now that is a pretty strong statement from this generally reputable vendor, so I put the question to Koni. Three times. The first two times they addressed other questions, but ignored my concern about their vendor's statement Koni does not approve or warranty FSD dampers for tourings. The final time I asked the question, their reply was "They should work." Apparently they are unable to say, "Yes, they WILL fit your E91, we guarantee it." Highland Pete, on the other hand, had actually been running the same model number on his 320d E91 for five years, with good results. I asked him why he took a chance and he said he contacted Koni support in Western Europe and they assured him it was a fit.
So I found a vendor in Southern California who not only had them in stock (“we have three sets in our warehouse in Michigan right now”), but even with the sales tax they came out significantly less than any of the other vendors would have charged if they had them, which they didn’t. And less than a week later, Federal Express delivered them to my door.
The ride on the touring from the factory is a bit harsh, noticeably more so than the ride on our E93. Up until I got behind the wheel for the first time with the newly installed FSDs, accelerated through the first turn and came to a quick stop I was thinking, “I should have got the kit with the Eibach springs.” My thinking is now I am glad I didn’t. I’ve never ran the touring hard and never will, but if I have to do some quick maneuvering the handling is definitely better than it was with the OE dampers.
The biggest difference I noticed is the ride comfort. Some of it is the new Michelin non runflats I put on about 1,500 miles ago, but most of it is the new FSDs. I’ll test it some more on some twisties and particularly bad roads this weekend, with an open mind. But for now my initial impression is noticeably better handling and significantly more comfort. I’m taking a short cut home in a bit, through Turnbull Canyon, a road I usually avoid because of all the twists and turns. Now, I'm looking forward to the ride home.