Front suspension refresh - Koni struts, OEM mounts, tower reinforcements, powerflex black FCAB's
I had a couple days off of work (spring break is starting here - everything shuts down) and made the most of it. I installed new Koni front sport struts with new lemforder strut mounts and strut tower reinforcement plates. I went ahead and replaced the FCAB's as well since they looked worn, and chose power flex blacks on the recommendation of a friend who's driven, fixed, and tracked many BMW's. This was a challenging job since it was my first time doing a front suspension refresh. There's reasonably good DIY's online, but here's a few tips I learned along the way. Feel free to critique/correct in the comments if there was a better way to tackle these challenges.
1) You need a very unusual, thin 18mm wrench to remove/install the sway bar end links. I got lucky - I found one in the back of a tool drawer (pic below). But without it, I would have been up a creek. There's flats on the sway bar housing, but they are very thin and bounded, so you can not get a normal open wrench on them. This was one of those moments when I felt like BMW engineers must have a competition with one another over who could design a part that required the most obscure tools.
2) Spring compressors take some trial and error. The stock springs on stock struts require a LOT of compression. Below is a picture of the setup that finally worked for me. I did, unfortunately, have to clamp the lower seat on the stock strut to get enough travel with the particular spring compressors I borrowed. That meant I couldn't remove the spring while compressed. I had to release it, move it to the new strut, and recompress. A power drill makes this go a LOT faster (or air tools if you have them).
3) Be very careful to make sure you get all the washers moved over to the new strut and top mount. As you'll see in the pics below, I missed one. I didn't realize it till I was cleaning up and saw that the old mounts didn't match! I had to remove the passenger side strut and add the washer. The good news was that by this point in time, my technique was much improved and the job only took about a quarter of the time.
4) It's difficult to loosen or tighten the top nut on both the stock and Koni struts. In both cases, the interface that allows you to hold the piston while turning the nut (a hex socket on the OEM units; external flats on the Koni's) is on the top of the piston... exactly where you need to get your socket to turn the top nut. There's a variety of specialty tools described online, which I did not have. Instead, I used vice grips with a 3" piece of old engine belt. It worked perfect. I was able to clamp the piston shaft with sufficient force to break the old nut free and torque the new nut, and there were no marks left on the shaft.
5) I will never again try to press old FCAB's out of their housings! That was incredibly hard. I ended up ruining my 3-jaw pullers (stripped threads). Just buy new lollipops with OEM bushings preinstalled - or get empty ones if you're doing poly like me. Here it is with the job done and new power flex bushes installed... finally!
Alright... so here's my first impressions after going for a spirited drive and impromptu autocross in an empty parking lot. The new Koni's are superb. They are soft at the moment since Koni wants you to do 500 miles at full soft. But the ride is so much improved. It's smoother, quite, and there's less jounce. I'm very pleased, and look forward to stiffening them up. The new FCAB's are also excellent. I expected them to be a bit harsh. They are not. Turn in is quicker and the car feels more responsive and planted. Overall, the front suspension is now tighter and I'm hearing less of the clunks and pops that I heard before. Now one caveat... I was replacing stock struts with 100k miles on them. So ANY suspension would be an improvement
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Originally Posted by Vas
