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Koni Yellow/Eibach Pro on Xi - Jittery rear axle
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05-11-2013, 11:02 PM | #1 |
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Koni Yellow/Eibach Pro on Xi - Jittery rear axle
Hi Guys ~ Need some help here.
Just upgraded my '11 335xi to Koni Yellow/Eibach pro. The handling is great but the back-end seems to shift when I drive over an uneven surface e.g. manhole cover, potholes, cracks, etc. For example, drive over manhole cover on passenger side, rear of the car shimmies left then back to the right. Same on the driver side but not as prevalent. It feels like the body is moving, as the wheel/tire are planted to the road. The car was aligned by the installer after the upgrade. My local BMW dealership has also checked out the install and reported everything to be tight and realigned the car (again) in trying to resolve the issue, but it's still there. The car is riding on 18" staggered Michelin PSS RFT. Any thoughts or suggestions would be greatly appreciated. Thanks! |
05-12-2013, 06:07 AM | #2 | |
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05-12-2013, 07:24 AM | #3 |
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That's because of our crappy subframe bushings on non-M cars. Getting better shocks simply revealed the deficiency that was already there.
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05-12-2013, 08:38 AM | #5 |
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That was one of my thoughts as well. e.g. stiffening up the rear, but others have gone the Koni/Eibach combo without issues. So wanted to get feedback before possibly spending more $.
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05-12-2013, 08:50 AM | #6 | |
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Also were the rear bump stops trimmed? You need to take 1" off them in back. Fronts need to be trimmed too or use e36 M3 stops. You could be riding on the stops (this just occurred to me). All kinds of shit could go wrong that would not nec be apparent from casual inspection, springs not seated properly, missing/misaligned spring rubber pads, improperly assembled under-tightened shock mounts. etc etc. Not sure who your installer was or how well he knows BMW's. If this were my car I would take it all apart and start over. As for the rear subframe bushings, yeah they are "weak" but that only shows up on hard launches and super hard cornering. Over ordinary road imperfections you should not be experiencing what you're describing. |
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05-12-2013, 02:15 PM | #7 | |
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I do agree that the dealership most likely did a superficial check. Therefore my next step is to bring the car to a local BMW specialty shop and them take a look. I will provide an update after the visit. Thanks again for the input! |
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05-12-2013, 02:31 PM | #8 | |
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There are procedures on line @ Koni's website make sure you are looking at the right one for your car and then the right end of the car. Rears esp are hard to get the rod fully compressed and seated into the adjuster mechanism, and then held there while turning. |
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05-12-2013, 06:25 PM | #9 |
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I respectfully beg to differ re: subframe bushings. I feel them squish sound all the time in normal driving conditions and cause exactly the same feeling the OP described... On stock zsp suspension.
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05-12-2013, 07:44 PM | #10 | |
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I'm not seeing how you can conclude bushings are at fault on OP's car when you haven't even verified bushings are the problem on your own car. My car does not do this, I am running koni/eibach 335xi, 18" OEM staggered wheels but non RFT conti DWS tires. |
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05-13-2013, 12:19 PM | #11 |
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I got the eibach/koni combo. I can tell you the car still feels a little unstable over bumps like those you describe. Sometimes it feels like the car hydroplaned, sometimes its like a shake (like when a dog tries to shake water of its body). Cant really give you a better description. Car is not as planted as my old STI.
I just attributed this to the subframe bushings that seem to be fluid filled ones, rather than solid ones. |
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05-13-2013, 12:45 PM | #12 | |
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One of the things I did try yesterday, per Ajsalida's recommendation was to review Koni's specification and install procedure. What I found was that the rear shocks actually have 2.5 full turn, not 1.5 full turn (per the installer's verification during the install). Assuming that is the case, 1/2 turn from what I thought was "full soft" is actually 1.5 turn for the "real full soft" baseline. Short of removing the rear and restarting, I firmed up the front end to match e.g. 1.5 turns from full soft. This seemed to have made the car better, but now makes me wonder if both rear shocks are set up identically. Next step is getting it checked out by an independent BMW shop, when I get new tires put on. |
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05-13-2013, 01:15 PM | #13 | |
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However I am not ruling out the rear (subframe) bushings, enough people have complained about them, it is something I've read about and considered doing if I ever kick the power level up beyond where my car is now (Cobb stage 2+). It's just I drove my car a lot looking for what they were describing and I just could not feel it. And believe me I live in an area with some pretty rough roads. One question for both you guys, or all you guys reporting this who have K/E. What kind of tires? RFT or not, and then independent of that, what wheel sizes and widths. Finally what pressures? I also found 2.5 turns available and set them to 0.5 turns off full soft. Next time I have them off I want to try 1 full turn. I run 18" staggered with non RFT conti DWS, OEM sizes, set at 38 PSI F/R. The rear feels very planted esp on sharp transitions (like tucking back in after an aggressive pass), or getting on throttle coming out of a turn. edit: last thing, I forgot to mention. When I first installed these and did an initial alignment (I do my own), I did notice a jiggling at the rear. Then I went back again after a few miles of settling and did a full alignment, and also released the binding on all the rear bushings. Meaning I fully loosened the main control arm and the two rear suspension adjuster bolt/nuts, and let the car visibly settle full weight, tightened it all back up again, then completed the alignment off that base. Two things happened. The rear dropped another 1/4 or so, and the jiggling went away. If you do not do this the bushings are twisting against load at rest. Last edited by ajsalida; 05-13-2013 at 01:24 PM.. |
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05-13-2013, 02:25 PM | #14 | |
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Aligned twice as noted. Not sure how it was done the second time, but the suspension was installed with the frame supported and components tightened, then moved to the alignment machine. |
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05-13-2013, 02:58 PM | #15 |
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Don't know what to tell you mon, inclined to think at the very least the rear shocks are at or near full stiff. If you could change one thing it'd be dial them back to 0.5 turns off full soft. Unfortunately they have to be taken out to do that.
Somebody here invented a way to only need to drop the top of the shock out, leaving the bottom still attached. Wheel removed, you unbolt the upper mount, drop the susp corner til it comes out of the upper fender well, take the mount and and the bump stop off the rod, and adjust while still bolted into the lower arm. Next time I do this I'll try that but I haven't done it myself. Keep up posted and good luck. |
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05-13-2013, 03:02 PM | #16 | |
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05-14-2013, 07:12 AM | #17 |
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When I installed mine, I specified turns from full stiff, rather than full soft. So installer should have turned to full soft then to full stiff (counting) and then to the setting I wanted. This might have given me better knowledge of how they were set up (knowing how many turns are in the strut, which seem to vary)
I changed over to non-rfl (michelin) like 500 miles ago and the car feels way better now. This jitter is less pronounced. Tire pressure as defined in the car (i think its 38 back, 32 front). I once read that the higher tire pressure is to fix the understear that it receives from the AWD. I have not tried it with lower pressure on back. I like my ride right now. On a separate note. I got road force tire balance and it was awesome. Car was just gliding on the road. No vibration whatsoever. Too bad it didnt last long, due to these damn roads |
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05-14-2013, 08:16 AM | #18 | |
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05-20-2013, 08:37 PM | #19 |
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I have a e90 330XI and just ordered koni FSD w/ eibach prokit. i have the 18" OEM staggered wheels on non RFT conti DWS tires. Did you trim down your bump stops? Or use E36 bump stops? Is this absolutely necessary?
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05-21-2013, 04:56 AM | #21 |
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Considering that I have a 330XI will the E36 M3 fit for the front? I would prefer purchasing new ones for the rear instead of trimming them down, anyone know which ones i can get?
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