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Suspension question.

Discussion in 'E46 (1999-2006)' started by bha7176, May 29, 2012.

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    I am thinking of upgrading my 2005 330XI's suspension with the following:

    Bilstein HD's up front, Bilstein E36 sport shocks in the rear, with Eibach pro springs on all four corners and upgraded Rogue rear support mounts. Questions I have are:

    1. Do I need to replace other components, like spring pads, bump stops, etc while I'm doing the shocks, struts and springs?
    2. I think I will, but do I need to get an alignment after the work is done?

    A little more car history. Car has 112,000 miles. It's on Bilstein HD's upfront, Bilstein sports in the rear with stock (I think) springs all around. Springs have single brown stripes on them. I bought the car used, so don't know the history.

    I took the car for an alignment at my local BMW dealer and they said that the ride height is off on the car making it impossible to align it properly. That, coupled with the bouncy ride and see-sawing front to back accelerating / decelerating prompted me to change out the springs and rear shocks. I'll let the front HD's in place for now.

    The dealer did replace the FCAB's before the alignment - I could have done this myself but since they had the car and the parts I went ahead and spent the money just to have it done.

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    What's the rationale for different shocks front to rear? For balanced handling, I'd think the recommendation would be the same shocks at all 4 corners. Presumably stock springs wouldn't have the ride-height problem you mention, and any quality aftermarket springs specifically made for the car shouldn't either. If your car's a 2005, it's either an E46 or E90 (realoem.com shows E46 330xi production to the end of 2004), so it seems odd to me that it would have E36 rear shocks if it's not an E36.

    You have to remove the front struts from the car to replace springs, and it's advisable to get an alignment anytime the front struts are removed. If you intend to replace the front strut inserts/cartridges (ie, the front shocks) eventually, if you don't do it when you replace the springs, you'll be duplicating that effort and labor, and the alignment, to swap out the shocks later.

    I think minor things like spring pads and/or bump stops are reasonably long-lived and unless they're visibly damaged or worn, there's probably little reason to replace them. If you have the front struts out, that's the time to install a new strut-mount bearing, or eventually face the same labor and alignment costs as for replacing front springs or strut inserts when the strut-mount bearings ultimately need replacing.

    But, going to that much effort, what's the intended usage? If you intend to track the car at driver's schools or auto-x, that path would guide one set of considerations, and primarily street driving with a priority on maintaining street drivability and ride quality would entail a different focus.

    Before starting to throw money at it, see if you can figure out what kind of springs you have on it. Perhaps the easiest and minimum thing to do is get the shocks matched up - if you know for sure the front has Bilstein HD's, installing the same shocks on the rear should give you an idea about ride quality, and hopefully address the oddball suspension dynamics you're experiencing. However, it's possible you have some generic or mismatched springs, or cheapo springs that are wrong for the car, and partially or fully to blame for the issue. Or, that sport shocks at all 4 corners is more in-line with what you hope to achieve, which would make buying a couple of different rear-shocks a moot point.

    If you don't know without a doubt what shocks you have and the springs are questionable, it may take a new spring set and shocks all around to get the car driving and handling in a balanced fashion. If you can figure out what's installed, then at least you have that as a comparison base for any package you consider. Obviously there's a huge range of suspension options out there for these cars and no shortage of choices - the hard part is figuring out what combination will give you what you want!
    two30grain likes this.
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    ^^^ +1.

    mixing and matching components in the way you have described can cause odd handling characteristics like MGarrison stated and can lead to unpredictable behavior. i wouldnt question this selection if you knew what you were looking for in the handling department and had an idea about what this setup changes the handling profile, but at the same time you are asking about bump stops etc. (i for one agree with MGarrison on springs pads, bump stops, etc., and def replace the bearings while you are in there, they are cheap).

    sorry to be blunt, but just keep in mind that sport springs have less travel then standard (which include HD's) and using them with anything other then sport springs is inadvisable. same for the vice versa. For OEM springs/ride height, use OEM or HD struts and shocks, and for sport springs use sports dampers. i believe Eibach pros drop 1.5-2.0", so def use sports with them. and do the same thing front to rear unless you are trying to obtain a particular result like removing the designed understeer. and if thats the case, make sure you are awake in the twisties! ;)

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