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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > All-Wheel-Drive (Xi / xDrive) Talk > Koni Yellow/Eibach Pro on Xi - Jittery rear axle



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      06-04-2013, 08:30 PM   #45
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Originally Posted by RX_AGENT View Post
I got the rear tucked look too after my install last weekend. I didn't expect the Eibach drop to be this low in the back.

Its a nice looking drop though!
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      06-04-2013, 08:47 PM   #46
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Originally Posted by RallyRcrr View Post
What kinda of $$$ are you talking? Can you point me to a specific part or set of parts? I'm interested in some suspension upgrades. Bushing and suspension work aren't an issue for me, and can get those swapped out relatively easily. So what does that leave me for pricing out the bushings? I'm assuming all you're talking about for the rear is a bushing set and sway. Is there anything else?

BTW, I did do a search but couldn't locate anything concrete as far a link to parts or a part number to search. Tried going through Grinchboy's possible locations, but no one gave any specifics for a 3 ser. I found bushings online for a 3, but is there are particular set? Any info you can give would be helpful. Thanks!
I haven't done this, but lots of people have. Google it or searched for it on this forum.

Here are some links
http://www.e90post.com/forums/showth...=698705&page=2
http://www.e90post.com/forums/showthread.php?t=230973
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      06-05-2013, 12:16 AM   #47
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Quote:
Originally Posted by RallyRcrr View Post
What kinda of $$$ are you talking? Can you point me to a specific part or set of parts? I'm interested in some suspension upgrades. Bushing and suspension work aren't an issue for me, and can get those swapped out relatively easily. So what does that leave me for pricing out the bushings? I'm assuming all you're talking about for the rear is a bushing set and sway. Is there anything else?

BTW, I did do a search but couldn't locate anything concrete as far a link to parts or a part number to search. Tried going through Grinchboy's possible locations, but no one gave any specifics for a 3 ser. I found bushings online for a 3, but is there are particular set? Any info you can give would be helpful. Thanks!
M swaybar kit
http://www.ecstuning.com/ES248879/

M Bushings
http://hpashop.com/BMW-Rear-Subframe...e-bushings.htm
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      06-05-2013, 12:19 AM   #48
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http://hpashop.com/BMW-Rear-Subframe...e-bushings.htm
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      06-05-2013, 12:21 AM   #49
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http://hpashop.com/BMW-OEM-M3-Rear-A...bar-e9x-m3.htm
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      06-05-2013, 06:28 PM   #50
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Thanks for the links!!
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      06-09-2013, 10:13 PM   #51
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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 10:27 PM.
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      06-09-2013, 10:35 PM   #52
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Quote:
Originally Posted by ajsalida View Post
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.
NICE!!!! Thanks for the update and good work! I was thinking about adding the M3 sway bar/bushing as part of the spring swap out to ZSP. Now, you went with the M3 rear sway, M3 bushings, the bushing inserts, and the Koni at 1/2 turn from full soft, interesting... Part of my upcoming spring swap out was going to include dialing back the rear Koni to 1 turn from full soft. If it still as compliant as you say, may be I will dial it back further. Love to hear an update after a couple days/weeks of driving.
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      06-10-2013, 06:21 AM   #53
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Quote:
Originally Posted by thegrinchboy View Post
NICE!!!! Thanks for the update and good work! I was thinking about adding the M3 sway bar/bushing as part of the spring swap out to ZSP. Now, you went with the M3 rear sway, M3 bushings, the bushing inserts, and the Koni at 1/2 turn from full soft, interesting... Part of my upcoming spring swap out was going to include dialing back the rear Koni to 1 turn from full soft. If it still as compliant as you say, may be I will dial it back further. Love to hear an update after a couple days/weeks of driving.
Well on the dialing back to 1 full turn off soft. Couple of things. If that other thread you posted up about spring rates was right about rear Eibachs being linear and stock rate then adding a bigger bar, stiffer bushings and stiffer rebound onto stock rate is a lot. Full soft they are already stiffer than stock shocks. Something to consider.

Other thing is people tend to not understand all the functions of rebound on shocks. First since it is a damper it resists motion, with force proportional (roughly) to velocity of piston rod. But there are low piston speed and high speed effects. Keeping the tire on the ground over bumps is one, the other is governing rate of chassis dynamics and weight transfer (F/R side side and corner corner). The latter is more a low speed function.

Point is a softer setting lets weight transfer faster. A bigger rear bar already slows down the side-side roll, stiffening up the shocks will slow it down more. I was thinking after my test drive I might want to slow down the weight transfer in front, that is stiffen up the front a little.

Too much rebound will also slow down the high speed damping, and that is why for example when people complain about rear feeling loose over bumps I ask what their shocks are set to. To much rebound WRT wheel travel over bumps will not let the susp extend fast over small bumps so tire does not stay in optimal contact with the ground.

Trick is finding the softest settings that do everything well and playing the low speed chassis dynamics against high speed tire behavior over surface irregularities.

edit: and that is with only rebound adjustable. Compression damping and sway bars on many cars are also adjustable, some with separate high and low speed damping.
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      06-10-2013, 07:46 AM   #54
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Shock dyno plot (off Koni's website) for Sport shocks with adjustable rebound. Also called force-velocity curves, just to give folks an idea of what the sports are doing. Velocity is piston velocity (inside the shock body), or how fast suspension is moving in rebound or compression You'd need motion ratios to figure wheel rates but in the industry they use piston velocity. Force is the force opposing motion. Note OEM curve vs full soft.



So this is not explicitly off our 335xi shocks but probably represents Koni's philosophy on a street performance rebound-only adjustable. Note compression is very close to OEM, maybe a little stiffer at low piston velocities.

At higher piston speeds there are internal blow off valves which prevent too much force being generated, this is why the curves roll over. Quite a lot of design goes into shaping these curves for various applications by the various manuf.

Point here is pick a piston speed at the lower end of the X-axis, and move up to the first green line. That is how much force is resisting weight transfer (unloading of that corner). Now move up to middle or higher point along the same x-point vertically. That is how much force is resisting weight transfer 1 turn. We don;t know units but it is clear full stiff could be 3-4 times as much force as stock. Also these are not linear (I have been told) WRT turns so you may be full stiff by 1.5 turns.

So imagine you'd cranked the rears to 1.5 off full soft, have Eibach pro kit (same spring rate as stock) but 3-4 times the force resisting extension of the shock for weight transfer, and maybe 2-3 times for keeping the tire in contact. No wonder other bits in the chassis flex first.

Last edited by ajsalida; 06-10-2013 at 07:59 AM.
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      06-10-2013, 04:24 PM   #55
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Quote:
Originally Posted by ajsalida View Post

So imagine you'd cranked the rears to 1.5 off full soft, have Eibach pro kit (same spring rate as stock) but 3-4 times the force resisting extension of the shock for weight transfer, and maybe 2-3 times for keeping the tire in contact. No wonder other bits in the chassis flex first.
Agreed. Thus the slippery slope of upgrades

I know at some point I will want the M3 rear subframe bits, just don't want to pay to have the back of my car taken apart again (and again) thus the consideration of just doing it once (again) and adjusting the Konis to a stiffness that I can live with long term. Given that I am currently at 1.5 off full soft at the rear (and mostly OK except for the chassis flex previously discussed), the thought process is that dialing it back to 3/4 or 1 off full soft should be livable even with the M3 bits. Of course would still like to hear your experiences with your upgrades before committing.

Last edited by thegrinchboy; 06-10-2013 at 04:40 PM.
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      06-10-2013, 04:29 PM   #56
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OT but not that much, Nice video of massive understeer...e46 m3 getting totalled off a cliff

http://www.youtube.com/watch?feature...&v=BkasHdSb1nQ
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      06-10-2013, 04:37 PM   #57
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Quote:
Originally Posted by thegrinchboy View Post
Agreed. Thus the slippery slop of upgrades

I know at some point I will want the M3 rear subframe bits, just don't want to pay to have the back of my car taken apart again (and again) thus the consideration of just doing it once (again) and adjusting the Konis to a stiffness that I can live with long term. Given that I am currently at 1.5 off full soft at the rear (and mostly OK except for the chassis flex previously discussed), the thought process is that dialing it back to 3/4 or 1 off full soft should be livable even with the M3 bits. Of course would still like to hear your experiences with your upgrades before committing.
Sorry my mistake I thought you had dialed it back already and were going MORE stiff. Def dial it back some, 1.5 will be way too stiff. If it helps the stuff you need to do to adjust rear shocks does not cross over or have anything to do with dropping subframe or swapping springs.

The main thing for shock adjust is jack up rear of car, remove wheels, remove carpet drop out top of shock and mount, disassemble top shock mount and bump stops/dust boot. Adjust while shock bottom still bolted on the control arm.. Reassemble.

Except for jack up rear and remove wheels nothing else crosses over. It is way easy compared to the other stuff. In fact you might want to do it first while you contemplate other stuff. Swapping springs is super easy at that point too, maybe do that with the shock adjust as a first step.

Subframe bushings (M3 is far harder than just inserts and that was already hard enough) and rear bar are a bear.
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      05-02-2014, 03:50 PM   #58
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Is there a possibility that the jittery ride is the shock bottoming out on the rear? Has anyone measured the length of a Koni shock vs. stock?

Would be interested to know how much suspension travel is lost when an X Drive car is lowered.
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      05-02-2014, 04:32 PM   #59
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Quote:
Originally Posted by Stackedacc View Post
Is there a possibility that the jittery ride is the shock bottoming out on the rear? Has anyone measured the length of a Koni shock vs. stock?

Would be interested to know how much suspension travel is lost when an X Drive car is lowered.
Was not really ever bottoming out, unless with larger speed bumps or raised driveways.

Since the last update, I have gone to/through the following setups.

ZSP springs, Koni Yellows at 1/3 range from full soft, UUC F/R sways = Great drop (secondary importance), comfortable ride (important to the wife) but unhappy with spring loading during spirited cornering/driving as ZSP are progressive (drove me insane)

Now:
Dinan springs, Koni Yellows at 1/3 range from full soft, UUC F/R sways = OK drop (too much in back, but again secondary importance), firmer ride (which I like), linear spring compression and feel
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      05-04-2014, 12:18 PM   #60
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I still have the stock suspension and it bottoms out in the front with a loud 'bang' all the time. Super annoying. I was going to put on Koni and ZSP to try and fix that but I'm no longer certain that it will help. Apparently KWs don't bottom out at all...anyone have any experience with KWs bottoming out?
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      05-06-2014, 11:23 AM   #61
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Stackedacc - I experienced that problem (often described in threads as 'pothole explosion') with a 335xi I bought with 50K miles. Not clear to me if that was 'normal' behavior or if my shocks were bad. In any case, installing Koni FSBs completely eliminated the problem with no other changes to the suspension or tires. Don't know if Koni yellows will solve your problem but my guess is that any aftermarket shock will.
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