OK I just finished the Whiteline bushing insert and M3 rear swaybar install on my 2009 335xi e92. Took most of a day and I am beat. However the test drives made it all worth while. I tend to not like doing two or more things at once to suspensions as it is hard to parse out what did what. But dropping the subframe twice I did not want to do.
Basically, tendency to plow/understeer into corners is gone. Very stark difference in turn in and steering feel. You can feel the outside front load up and bite as weight transfers onto it, very clear and predictable shift across diagonal inside rear to outside front. Overall went from a neutral to frequently understeering car under aggressive driving to a more neutral very slight oversteering car. This is mostly the M3 bar and I am sure the busing inserts helped keep things nailed down. This was the coupe/sedan bar not the bigger vert M3 bar. Bar was still massive compared to stock but hollow (tubular). Note I have Koni sport set 0.5 turns off full soft, and Eibach pro kit.
Where the bushing inserts were very apparent was on washboard dirt. I live on a dirt road and the car always got a little unpleasant on this stuff (washboard). But literally first 30 seconds out of my driveway I was tooling along and realized, whoa I am flying over this washboard and it feels great. So comments about nailing down the rear subframe and letting the suspension work are dead on. I never noticed the rear misbehaving on flat asphalt, now it just seems much more planted.
OK on to other stuff. No change in ride height which was not surprising when you look closely at how the inserts fit into the bushings. There are large voids in the stock bushing and what appears the be thick parts of the inserts slip up into those voids and fill them. Once everything is compressed I doubt there is 1/8 to 1/4 inch overall added to thickness, and then only half that (the upper half) pushes the subframe down WRT car. Furthermore the springs set up into the unibody (not the subframe) so they take the load at the same point and compress the same amount. My car has 34k miles, stock subframe bushings looked great no tears or rot. So maybe others who were experiencing bad shake or slop their stock bushings might be gone already. I never felt that but I do feel the difference now.
Install notes. I thought installing down pipes on an XI was hard. This is twice as bad. The bushing inserts would be an easier job (say 3 hrs tops), the sway bar was a bear though just no room up there for a much thicker bar. Oh yeah, put the brackets/bushings on the bar BEFORE you spend 1.5 hrs trying to get the bar threaded though the mess underneath there. The M3 sway bar bushings are hard delrin/poly/rubber and 2 halves need to be pressed into each other around the bar and snap into detents in the M3 sway bar bracket. I must have spent 2 hrs getting those friggin things onto the bar with the bar already on, then lubing/sliding the assembly into position. I used some carpenter's clamps, even then it was very difficult.
I did a lot of unnecessary stuff, too. Dropped the exhaust, don't need to do that. Took off the rear X brace thing, that could stay. Etc etc. Had a hell of a time getting the upper strut arm thing's bolts threaded into the rear hubs, kept wanting to partially strip them and that was stupid. Turn out you need to put a jack under the control arm and jack it back up a bit AFTER you raise the subframe back up & bolt everything else back on, and they go in fine.
I have to get back under there again and check a few things, reTQ big bolts etc. I was getting a slight clunk on hard accel couple of times on 3-4 upshift in sport mode, may be the exhaust. I noticed one side tailpipe outlet was maybe 1/4" lower than the other I could have forgot to TQ down an exhaust hanger nut or two. Was completely wiped at the end of this, very demanding physically.
This was one of those jobs where your forearms cramp up so bad when you try to type after, like now, just crazy. Anyway more later as I nail down a few things, overall great mod. Major handling improvement without any added harshness.
PS: I did not know this before I bought them but the Whiteline inserts are the same or substantially the same as the powerflex inserts. They look identical but the Whitelines cost over 2/3 less than what the powerflex do. I got mine $45 shipped no tax. There are some DIY and Q&A in the suspension section on powerflex, good reading.
Last edited by ajsalida; 06-09-2013 at 11:27 PM.