[Doyle]

The back half of the xi is exactly the same as the regular "i". Anything will fit. Check the sticky up top for more info.

CobraMarty-
I have not tried the UUC sways, personally. I have read that there are some fitment quality issues, but who knows? I called to get some more specifics about their bars (arm lengths) and I got the sell that "you can't compare one company's product to another". Yeah, right. Without that info, it is tough to get figures.

However, most knowledgable members say that as long as you have stock spring rates (stock springs or eibach springs), the UUC bars should work fine. Just don't go crazy adding them to other setups. Just because it handles flatter does not mean it handles better.

[CobraMarty]

I can pull the bars out of the box and measure what you need.

[Doyle]

CobraMarty-

That would be awesome!



Since the rear bar is adjustable, measure the above from each hole (in mm). The front should be pretty straightforward.

Also, if anyone else wants, we can try to compile some data points for reference. Feel free to submit/PM the above measurements of your bars.

For reference (data from Orb):

Stock Rear Bar wheel rate - 42.19 lb/in
E90 M3 Rear Bar wheel rate - 109.53 lb/in

[CobraMarty]

OK here is what I measured, the bars are for 328xi coupe E92 if that matters.

Rear: A1=8.125", A2=9", B=30.5", C=12.5", D=19mm
Front: A=9.25", B=30", C=10", D=27mm

Tires and wheels: Front 225/40x18 +5mm spacers, Rear 255/35x18 +15mm spacers.
Stock shocks and springs.

[Doyle]

Results for running the UUC bars with stock suspension:

Goals-
Total Roll: 1.8-2.5'
Total Load Transfer: 56.9-59.9 (with ~57.4 being the sweet spot)

Stock-
Total Roll: 2.99'
Total Load Transfer: 65.44

Both Bars (rear full stiff)-
Total Roll: 1.72'
Total Load Transfer: 68

Rear Bar Only (full stiff)-
Total Roll: 2.59'
Total Load Transfer: 58.06

So, obviously the best choice is returning the front bar, and keeping the rear on full stiff. Otherwise the understeer actually gets worse. This is consistent with what Orb has recommended to xi owners in the past -- the front bar is just WAY too stiff.

[UltraRacer13]

do you mind me asking for you to "show your work" on that math? I have no idea where you are getting these numbers.

[CobraMarty]

Interesting results. It shows everything is a comprise. Using both bars decreases total roll and slightly increase TLT. Rear bar only slightly decreases total roll but brings TLT to a much improved spot. So both bars gives a 'better street' feel (less body roll) but rear bar only gives better handling.
The front bar is easier to install and gives a 'better feel' with less body roll compared to the rear bar which is harder to install but would be better.

Can you calculate with only the front bar? Thanks.

[IN54NITY]

Great reading Doyle. Thank you.

Off topic: FYI, I just went in to my local shop www.bimmerhaus.com for an alignment, get less toe in for rear, and get max camber out of Vorshlags. To the point, unfortunately I could only get -2.5d for camber out of fronts. I don't know why I can't get an additional -.5d. I need to take a wheel off and see. It's disappointing considering front tire outside shoulder wear I was getting. (TXSailor, my bad, but I was only at -2.2d before up front.) My rear camber is at -1.9d, and this seems to be good for this car.

[Doyle]

TXSailor-
No problem. Attached is a worksheet obtained from Orb that has pretty accurate assumptions. All of the calculations are validated and based off of Milliken's work. Since you can't attach excel doc's, just right click and save target, then right click the icon and "open with excel".

CobraMarty-
UUC F Bar, Stock R
Total Roll: 1.89'
Total Load Transfer: 73.73

I would not advise this at all, lol.

aleckzandr-
There can be a few reasons for not being able to get additional negative camber. If you are using OEM shaped springs (like what comes with all xi coilover kits, except AST and HPA Swift conversion) then it is likely the large diameter of the top of the spring and spring perch is preventing anymore negative camber. If you do have 60mm springs, then further investigation may be needed.

Also, depending on your current spring rates and suspension choices, you may be getting excessive understeer.

[CobraMarty]

So will widening the front track 10mm and the rear track 30mm decrease the total load transfer?

[Slops]

Doyle, you have some great information in here and thanks for contributing . I feel so out of place here because I do not track my car at all, but figured i'd start investigating some options as many has done before on how to just lower that front a little bit so it doesn't look like a 4X4. The non-xi models looks pretty nice with a full wheel well and here i come with my brand new car looking like i'm ready for some off-roading

I like the stock handling, but i do feel that at some brisk runs that the car doesn't feel as planted even going straight. It feels a little wobbly ... SO i'll subscribe to this thread until i can figure out what I need to help this. The backroads seems to handle nicely as i do drive the shit out of it when i get the chance. The only upgrade i was thinking later down the road was the KW V1's.

[Doyle]

CobraMarty-

Widening the front track relative to the rear will decrease front load transfer. The opposite is also true.

Sloppy-

No problem. I don't think may xi owners actively track their cars. Most are looking for exactly what you want. For your situation, bilsteins and eibachs will probably be fine. V1's are decent if you want to have height adjustability, but the spring rates are pretty out of whack.

Also, the bushings the cars are equipped with are largely to blame for the "wobbly" or disconnected feeling.

[Slops]

I wish the stock suspension was hight adjustable - haha. Only reason i'm looking at the V1's are because of hight adjustment. I'm just concerned about how well they would fit for my driving style and of course I would love the ride quality to be similar to that of a stock xdrive. Most people on here that have them says its a little harsher but not bad at all... so I dont know. 2K is a lot of money to do a trail and error

[Doyle]

Sloppy-

Pretty much the only thing that the V1's have going for them is ride height adjustment. If you NEED height adjustment, then I would personally save up for a couple more months and get the AST's. Why sacrifice ride and performance for looks? You can have your cake and eat it, too.

[Slops]

Originally Posted by Doyle

Sloppy-

Pretty much the only thing that the V1's have going for them is ride height adjustment. If you NEED height adjustment, then I would personally save up for a couple more months and get the AST's. Why sacrifice ride and performance for looks? You can have your cake and eat it, too.

i'm a total noob when it comes to suspension as i've mentioned before. Thanks for your advice so far. I dont mind paying a bit more if i can eat my cake too. I'm not familiar with AST. Do you have a link to their website please?

I looked here but they dont seem to offer 2011 E90 xi suspensions parts... http://www.ast-usa.com/ast-4100-shoc...ilover-kit.php

[UltraRacer13]

Originally Posted by Sloppy

i'm a total noob when it comes to suspension as i've mentioned before. Thanks for your advice so far. I dont mind paying a bit more if i can eat my cake too. I'm not familiar with AST. Do you have a link to their website please?

I looked here but they dont seem to offer 2011 E90 xi suspensions parts... http://www.ast-usa.com/ast-4100-shoc...ilover-kit.php

Call or email Brian Hanchey at AST- He'll hook you up. Or call Harold at HPautowerks.com. He is pretty much the suspension guru and sells the AST's. He will be able to consult with you to determine the best setup for your needs.

[itsbrokeagain]

Good info in here

[Fozzy]

Originally Posted by Doyle

Sloppy-

Pretty much the only thing that the V1's have going for them is ride height adjustment. If you NEED height adjustment, then I would personally save up for a couple more months and get the AST's. Why sacrifice ride and performance for looks? You can have your cake and eat it, too.

Doyle, you are no doubt much more knowledgable than I am, but from what I've read most people prefer the ride of the V1 over a Blistien/ Eibach set up. My impression is the combination of comfort and handling is better with coils. The adjustment is a bonus, as with the springs they aren't lowering the vehicle much and the rake could be exacerbated, expecially on an xi.

Can you talk more to this? I'm not looking to slam the car and adjustment isn't critical, but comfort, tightened ride and lowering to around non-xi height is desired. Thanks for the input.

[Lenaxia]

I'm also curious about the same things as Fozzy, but also on a few other things.

From what I've read pretty much everyone who uses the Bilstein B8's use them with H&R springs. However because H&R doesn't release their spring rates I'm not too keen on going that path. On the other hand, I haven't found any references to a B8/Swift combo. Is this because it doesn't work at all?

Also, I've been playing around with the spread sheet you posted, but I can't figure out whether I need to enter in damper data or even where to find it as it seems no one has that information for most systems. Also, do we have numbers for the M3 rear sway?

[Lenaxia]

Also, another quick question: Why is a WT Bias targeted at 3-6% higher than the weight distro instead of having it the same. Or more specifically, what makes 3-6% such a special number?

[Doyle]

Fozzy-
Have these people owned and/or ridden in both back-to-back? I'm curious since the spring rates that come with the V1's are too low for performance, and the natural frequencies are almost dead even front to rear. This means ride settling, pitch, and oscillation will be way off. There are plenty that enjoy the Bilstein/Eibach ride. Search around. My guess is there is quite a bit of buyer's rationalization (the same reason every tune owner thinks their particular tune is the best).

"Ride comfort" is usually felt as the proper pairing of spring rates and shock valving. This is why the AST owners can run 400/800 rates and the ride is felt as "smoother" than H&R's on stock shocks. V1's are valved for their matched springs, just like Bilsteins are valved to match the stock springs, and accordingly, the eibach springs. "Ride comfort" will likely be the same, but the car will oscillate poorly with the V1's. Your passengers will pick up a feeling of queasiness.

That being said, neither of these are performance oriented suspension setups. They are best for the DD that likes to take onramps a little quicker.

Lenaxia-
I agree. I'm hesitant to buy anything, from any provider, if they aren't willing spill the details.

The B8/Swift combo was something that I was hoping would work out. The swift website shows that they are R&D'ing some lowering springs. Those haven't been released, yet. The other route was using the B8's with a coilover sleeve and 2.5" ID Swift springs. This is popular with the miata and supra guys. I recently talked to Bilstein and they said there was no way that that would work for these cars.

The damper data isn't important to the load transfer worksheet. If you work with shops/people that know what they are doing, than they will do that hard work for you. The intricacies of damper valving is waaaaaay beyond my understanding.

If you want to increase your basic knowledge of what to look for in valving charts, read these:

http://www.optimumg.com/OptimumGWebS.../TechTips.html
http://farnorthracing.com/autocross_secrets6.html

As far as "the magic number", that is a baseline recommendation by Milliken. It basically means that more of the roll gradient is taken by the front of the car. This will read as neutral to the driver. Around 5% is the rough goal. From there, changes can be made to suit the driver's needs. For example, some autocross drivers love tail-happy cars. They will usually have a magic number of 0%, or so.

For the average driving enthusiast, this magic number range will lead to a more than capable car. Who here can say that they can wring every last drop of performance out of an e90 M3? I know I can't!

[Lenaxia]

Thanks for the clarification Doyle!

I did have some questions about the Bilstein stuff though.

I think I'm missing some knowledge in regards to the kind of springs that exist, but if Swift hasn't released lowering springs for the e90 xi, then what are the AST4100's using that Harold put together? I know they're using swift springs with that, and on their website they say they're using 60mm ID swifts.

What's the difference between what they did for the AST's and using coilover sleeves with 2.5" ID swifts?

Is there something inherently different between the B8's and the AST's that allow the ASTs to use swifts and not the B8's?