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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > All-Wheel-Drive (Xi / xDrive) Talk > Xi suspension- my $.02



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      08-30-2012, 09:00 PM   #1
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Xi suspension- my $.02

Just sharing some experience tuning the suspension on an xi..
As you know, our cars tend to understeer.. The rwd's as well, but I think its worse on the awd platform..

In order to rectify this problem I first went and replaced the springs with Eibach ones.. I noticed the car was a bit more planted.. And there was significantly less body roll..

Step two was to replace the rear sway bar (what a flimsy POS) with an m3 one.. As was the recommendation from Sal at Autocouture to also replace the rear subframe bushings with m3 ones.. I did this probably six months ago.. So this is a bit overdue

What I've found is that the car feels SO much more balanced.. Understeer has been Dramatically reduced.. And dare I say it, i can even get the car to oversteer.. Turn in feels very sharp.. And the car feels the way it should have from the factory.. I will update this as soon as I install the Bilstein sports

I'm sure alot of you are running coilovers or lowering springs, but I HIGHLY recommend this mod.. It makes a big difference
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      08-31-2012, 04:44 PM   #2
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Having the rear end on the XI feel a tad bit soft is excatly what i thought about when i drive it. Is that rear sway bar adjustable? Did you any of the tires get kicked out further than the stock bar?
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      08-31-2012, 04:57 PM   #3
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Thanks for the info! How are the Eibachs on the stock struts?? also how does the stance look, any reverse rake??

Quote:
Originally Posted by BAL278 View Post
Just sharing some experience tuning the suspension on an xi..
As you know, our cars tend to understeer.. The rwd's as well, but I think its worse on the awd platform..

In order to rectify this problem I first went and replaced the springs with Eibach ones.. I noticed the car was a bit more planted.. And there was significantly less body roll..

Step two was to replace the rear sway bar (what a flimsy POS) with an m3 one.. As was the recommendation from Sal at Autocouture to also replace the rear subframe bushings with m3 ones.. I did this probably six months ago.. So this is a bit overdue

What I've found is that the car feels SO much more balanced.. Understeer has been Dramatically reduced.. And dare I say it, i can even get the car to oversteer.. Turn in feels very sharp.. And the car feels the way it should have from the factory.. I will update this as soon as I install the Bilstein sports

I'm sure alot of you are running coilovers or lowering springs, but I HIGHLY recommend this mod.. It makes a big difference
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      08-31-2012, 05:46 PM   #4
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I lowly recommend springs only. Ride will suffer and rebound will be subpar if you're going over bumps or imperfections.

I agree with the rest
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      09-01-2012, 03:46 PM   #5
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Quote:
Originally Posted by pits200
I lowly recommend springs only. Ride will suffer and rebound will be subpar if you're going over bumps or imperfections.

I agree with the rest
I agree with this.. Which is why I'm getting Bilsteins lol
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      09-01-2012, 03:49 PM   #6
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Quote:
Originally Posted by 802Bimmer
Thanks for the info! How are the Eibachs on the stock struts?? also how does the stance look, any reverse rake??

Quote:
Originally Posted by BAL278 View Post
Just sharing some experience tuning the suspension on an xi..
As you know, our cars tend to understeer.. The rwd's as well, but I think its worse on the awd platform..

In order to rectify this problem I first went and replaced the springs with Eibach ones.. I noticed the car was a bit more planted.. And there was significantly less body roll..

Step two was to replace the rear sway bar (what a flimsy POS) with an m3 one.. As was the recommendation from Sal at Autocouture to also replace the rear subframe bushings with m3 ones.. I did this probably six months ago.. So this is a bit overdue

What I've found is that the car feels SO much more balanced.. Understeer has been Dramatically reduced.. And dare I say it, i can even get the car to oversteer.. Turn in feels very sharp.. And the car feels the way it should have from the factory.. I will update this as soon as I install the Bilstein sports

I'm sure alot of you are running coilovers or lowering springs, but I HIGHLY recommend this mod.. It makes a big difference
The eibachs on stock struts.. It is livable lol.. I would recommend to upgrade them, but the drop isnt as aggressive as HR (imo the perfect amount of drop) so the ride isnt as harsh as those

Stance is great.. Could benefit from upgraded shocks.. I will update this when the Bilsteins are on
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      09-01-2012, 04:14 PM   #7
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Interesting. I'm not much of a suspension guy...I was thinking that the easiest way to reduce understeer on our cars would be to use camber/caster plates to get the front camber to match the rear. Due to liability issues I tend to assume that the factory has pretty much maximized the traction at the rear and not at the front to make sure there's plenty of understeer and that the fix is just a matter of increasing traction at the front.
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      09-01-2012, 05:16 PM   #8
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Quote:
Originally Posted by Carl Morris
Interesting. I'm not much of a suspension guy...I was thinking that the easiest way to reduce understeer on our cars would be to use camber/caster plates to get the front camber to match the rear. Due to liability issues I tend to assume that the factory has pretty much maximized the traction at the rear and not at the front to make sure there's plenty of understeer and that the fix is just a matter of increasing traction at the front.
I agree completely, Understeer is the "safe" route.. The rear sway bar is incredibly flimsy.. I'm sure camber would increase front grip, but from my experience with only these mods.. It does a fantastic job of balancing the car.. The rear end just feels too soft.. Using these M3 components makes a noticeable difference
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      09-06-2012, 03:51 PM   #9
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what is the part number for the Eibach springs you installed?
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      09-07-2012, 07:09 PM   #10
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Would this apply to coupe, sedan, or both?

Thanks,
Don Zielke
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      09-08-2012, 08:43 AM   #11
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I put kw V1s on last Dec. which markedly improved the floaty feeling, but still feel some sway in curves compared to my prior e92 non-x. Based on yours and others comments, am thinking of doing the rear M3 sway. However, a guy who runs a specialty bmw shop near me actually recommended against it, but I think he may not be as familiar with x-drive issues with suspension. How much should install run?
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      09-10-2012, 10:38 AM   #12
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Good tire pressure management can also go a long way to dialing out the understeer. On the stock setup before I upgraded, I found the bias to be pretty close to neutral (though it did still push a bit) with 32/36 F/R psi.

Combined with my new stuts, the car feels dramatically improved. I was thinking about a rear sway and bushings next, but given how much better the car feels, I'm probably going to hold off for a while.
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      09-20-2012, 08:48 AM   #13
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Quote:
Originally Posted by rwgeld58 View Post
I put kw V1s on last Dec. which markedly improved the floaty feeling, but still feel some sway in curves compared to my prior e92 non-x. Based on yours and others comments, am thinking of doing the rear M3 sway. However, a guy who runs a specialty bmw shop near me actually recommended against it, but I think he may not be as familiar with x-drive issues with suspension. How much should install run?
Install was about 4 hours for the Rear Sway and subframe bushings
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      02-02-2013, 01:04 PM   #14
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still available?
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      02-03-2013, 07:48 PM   #15
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Does the 22.5 m3 rear sway bar fit a 2007 e90 335xi
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      02-04-2013, 09:31 AM   #16
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Yes. All the E9x rears have the same config Sway. Just different thickness.
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      02-04-2013, 10:08 AM   #17
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Single best thing you can do to improve balance on a street BMW is add more front camber. The best way to do this, counterintuitively, is often to add a stiffer front swaybar to keep the front suspension in its happy place, because the front suspension geometry de-cambers the tire as it travels through its range of motion in bump. The E90 chassis is much better than past designs in this regard but still not as good as some double wishbone setups which can get by with less than a degree of negative camber and still keep the tire square to the road in a corner. A bigger rear bar just takes grip away from the rear especially under acceleration, what the car needs is more front grip
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      02-05-2013, 12:53 PM   #18
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Quote:
Originally Posted by Richbot View Post
Single best thing you can do to improve balance on a street BMW is add more front camber. The best way to do this, counterintuitively, is often to add a stiffer front swaybar to keep the front suspension in its happy place, because the front suspension geometry de-cambers the tire as it travels through its range of motion in bump. The E90 chassis is much better than past designs in this regard but still not as good as some double wishbone setups which can get by with less than a degree of negative camber and still keep the tire square to the road in a corner. A bigger rear bar just takes grip away from the rear especially under acceleration, what the car needs is more front grip
I though most would disagree to replace the front sway vs the Rear...
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      02-05-2013, 07:12 PM   #19
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Quote:
Originally Posted by MSport35TT View Post
I though most would disagree to replace the front sway vs the Rear...
Correct thats what iv heard too. Rear> Front , although what he said about front>rear does make sense as he explained .
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      02-11-2013, 01:36 PM   #20
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Changing out the swaybars and endlinks are usually the first step in tuning AWD suspension (well technically tires first). You will greatly benefit more from having stiffer swaybars/bushings prior to doing springs/shocks.

Coming from the Subaru scene this is quite common and companies like whiteline have a very good reputation and parts selection. Was quite surprised on how many BMW parts were made as well.

http://www.whiteline.com.au/do_segue...3%2F05-10%2F11
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      02-11-2013, 02:02 PM   #21
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Quote:
Originally Posted by SDV325 View Post
Changing out the swaybars and endlinks are usually the first step in tuning AWD suspension (well technically tires first). You will greatly benefit more from having stiffer swaybars/bushings prior to doing springs/shocks.

Coming from the Subaru scene this is quite common and companies like whiteline have a very good reputation and parts selection. Was quite surprised on how many BMW parts were made as well.

http://www.whiteline.com.au/do_segue...3%2F05-10%2F11

Unfortunately, such is not true with the bmw due to the complexity of swapping out the rear sway and needing to drop the subframe.
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      02-13-2013, 06:02 PM   #22
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with B8 bilstein's, correct? what is the part number for the Eibach's you put on?
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