[NM_BMW]

Originally Posted by Orb

You have no idea how badly KW screwed this car up. Your car has more under steer than stock simply because the spring rates in the rear only increased 23 lb/in at the wheel while the front spring rate increased 100 lb/in. The pitch balance is as backward from how BMW designed it. Mr. 5 has no idea about anything to do with roll bars so how can there be an approach….the blind leading the blind sounds about right.

There is a way to fix but no going to come easily or cheaply.

Orb

So are you saying that the 2k isn't worth it? Hopefully bilstien comes out with a nice setup by spring time.

[jgalaxy]

Originally Posted by Orb

You have no idea how badly KW screwed this car up. Your car has more under steer than stock simply because the spring rates in the rear only increased 23 lb/in at the wheel while the front spring rate increased 100 lb/in. The pitch balance is as backward from how BMW designed it. Mr. 5 has no idea about anything to do with roll bars so how can there be an approach….the blind leading the blind sounds about right.

There is a way to fix but no going to come easily or cheaply. The root problems are in ass end with both the springs and roll bar.
Orb

Might explain why I havent been too successful with any combo of adjustments on the KWs no matter what is done. Frustrating as hell.

[Kev]

Originally Posted by Orb

You have no idea how badly KW screwed this car up. Your car has more under steer than stock simply because the spring rates in the rear only increased 23 lb/in at the wheel while the front spring rate increased 100 lb/in. The pitch balance is as backward from how BMW designed it. Mr. 5 has no idea about anything to do with roll bars so how can there be an approach….the blind leading the blind sounds about right.

There is a way to fix but no going to come easily or cheaply. The root problems are in ass end with both the springs and roll bar.
Orb

As you have said earlier in our correspondence, KW designed the V3 with people who drop their car to the max in mind, so they sacrificed the handling in favor of looks. Not good in my books. By the way, I PM'ed you about the linear springs. I'm considering removing the UUC sway bars and going back to stock for now.

[Orb]

Originally Posted by Humtek

So are you saying that the 2k isn't worth it? Hopefully bilstien comes out with a nice setup by spring time.

Going by the Bilstein spring rate which are progressive peaks 390 lb/in front and 610 lb/in the rear is actually worse than the KW but maybe there is hope. At least with the Bilstein you can get linear spring and revalve the damper so you can get the right setup if someone gives you magic numbers.

The after market kits have been design for peg leg differential approach for suspension tuning. The progressive springs are not what you want on track car ever. The only way around is to put on a big friggen tire up front. This is just a Band-Aid and only delays the onset of under steer.

Originally Posted by jgalaxy

Might explain why I havent been too successful with any combo of adjustments on the KWs no matter what is done. Frustrating as hell.

I put my KW on about 6 months ago and lost 8 seconds a lap over my Koni FSD and H&R roll bar setup. I burned up 2 sets of front tires last year so getting this fixed to end has been something I have been working on every weekend since September. My KW v3 are going up for sale since I’m getting some real damper JRZ custom tune.

The quick solution is: 230 lb/in front spring on with an 800 lb/in rear spring. Put a UUC front sway bar on and buy H&R bushing to get rid of the crap ones that come with the bar. Buy a H&R rear bar which does fit the xi. The rear sub frame bushing will not work well with the incresed stiffness so you need to upgrade them M bushing. The bushings are cheap and the install is low for cost when doing a rear bar. You been warned if don’t replace the bushing the car will bounce around a lot and yu will not get good rear grip. There is two link in the rear you can also change to M link if you wish and they do matter a lot FWIW.

This setup will get you back to BMW OEM pitch which is a frequency of 12% higher at the rear than the front. The spring I selected is within the working v3 range.

The wheel spring rates are:

Front 215 lb/in (KW stock is 258 lb/in)
Rear 285 lb/in (KW stock is 205 lb/in)

In the mean time increase front rebound as much as you can...it is the only thing you can do.

How I got the info is much longer story……

Originally Posted by Kev

As you have said earlier in our correspondence, KW designed the V3 with people who drop their car to the max in mind, so they sacrificed the handling in favor of looks. Not good in my books. By the way, I PM'ed you about the linear springs. I'm considering removing the UUC sway bars and going back to stock for now.

I will PM you shortly.

Orb

[Kev]

JRZ makes some nice product and they also make some of the OEM products for Dinan. Too bad we can't copy your JRZ setup since our mounting positions are different...... I would love to have a squeak free, no coil binding, and appropriately tuned suspension setup.......

[MVested]

Originally Posted by Orb

Going by the Bilstein spring rate which are progressive peaks 390 lb/in front and 610 lb/in the rear is actually worse than the KW but maybe there is hope. At least with the Bilstein you can get linear spring and revalve the damper so you can get the right setup if someone gives you magic numbers.

The after market kits have been design for peg leg differential approach for suspension tuning. The progressive springs are not what you want on track car ever. The only way around is to put on a big friggen tire up front. This is just a Band-Aid and only delays the onset of under steer.




I put my KW on about 6 months ago and lost 8 seconds a lap over my Koni FSD and H&R roll bar setup. I burned up 2 sets of front tires last year so getting this fixed to end has been something I have been working on every weekend since September. My KW v3 are going up for sale since I’m getting some real damper JRZ custom tune.

The quick solution is: 230 lb/in front spring on with an 800 lb/in rear spring. Put a UUC front sway bar on and buy H&R bushing to get rid of the crap ones that come with the bar. Buy a H&R rear bar which does fit the xi. The rear sub frame bushing will not work well with the incresed stiffness so you need to upgrade them M bushing. The bushings are cheap and the install is low for cost when doing a rear bar. You been warned if don’t replace the bushing the car will bounce around a lot and yu will not get good rear grip. There is two link in the rear you can also change to M link if you wish and they do matter a lot FWIW.

This setup will get you back to BMW OEM pitch which is a frequency of 12% higher at the rear than the front. The spring I selected is within the working v3 range.

The wheel spring rates are:

Front 215 lb/in (KW stock is 258 lb/in)
Rear 285 lb/in (KW stock is 205 lb/in)

In the mean time increase front rebound as much as you can...it is the only thing you can do.

How I got the info is much longer story……



I will PM you shortly.

Orb

You are a wealth of knowledge, and I myself as well as others truly appreciate your dedication to a proper handling bimmer

[jgalaxy]

Originally Posted by Orb

Going by the Bilstein spring rate which are progressive peaks 390 lb/in front and 610 lb/in the rear is actually worse than the KW but maybe there is hope. At least with the Bilstein you can get linear spring and revalve the damper so you can get the right setup if someone gives you magic numbers.

The after market kits have been design for peg leg differential approach for suspension tuning. The progressive springs are not what you want on track car ever. The only way around is to put on a big friggen tire up front. This is just a Band-Aid and only delays the onset of under steer.




I put my KW on about 6 months ago and lost 8 seconds a lap over my Koni FSD and H&R roll bar setup. I burned up 2 sets of front tires last year so getting this fixed to end has been something I have been working on every weekend since September. My KW v3 are going up for sale since I’m getting some real damper JRZ custom tune.

The quick solution is: 230 lb/in front spring on with an 800 lb/in rear spring. Put a UUC front sway bar on and buy H&R bushing to get rid of the crap ones that come with the bar. Buy a H&R rear bar which does fit the xi. The rear sub frame bushing will not work well with the incresed stiffness so you need to upgrade them M bushing. The bushings are cheap and the install is low for cost when doing a rear bar. You been warned if don’t replace the bushing the car will bounce around a lot and yu will not get good rear grip. There is two link in the rear you can also change to M link if you wish and they do matter a lot FWIW.

This setup will get you back to BMW OEM pitch which is a frequency of 12% higher at the rear than the front. The spring I selected is within the working v3 range.

The wheel spring rates are:

Front 215 lb/in (KW stock is 258 lb/in)
Rear 285 lb/in (KW stock is 205 lb/in)

In the mean time increase front rebound as much as you can...it is the only thing you can do.

How I got the info is much longer story……



I will PM you shortly.

Orb

Thank you for sharing your hard work. I certainly know how much time and money I've spent on this. I'd be very interested in knowing what you've finally gone with to get your car balanced.

Cheers.

[NM_BMW]

Originally Posted by Orb

Going by the Bilstein spring rate which are progressive peaks 390 lb/in front and 610 lb/in the rear is actually worse than the KW but maybe there is hope. At least with the Bilstein you can get linear spring and revalve the damper so you can get the right setup if someone gives you magic numbers.

The after market kits have been design for peg leg differential approach for suspension tuning. The progressive springs are not what you want on track car ever. The only way around is to put on a big friggen tire up front. This is just a Band-Aid and only delays the onset of under steer.




I put my KW on about 6 months ago and lost 8 seconds a lap over my Koni FSD and H&R roll bar setup. I burned up 2 sets of front tires last year so getting this fixed to end has been something I have been working on every weekend since September. My KW v3 are going up for sale since I’m getting some real damper JRZ custom tune.

The quick solution is: 230 lb/in front spring on with an 800 lb/in rear spring. Put a UUC front sway bar on and buy H&R bushing to get rid of the crap ones that come with the bar. Buy a H&R rear bar which does fit the xi. The rear sub frame bushing will not work well with the incresed stiffness so you need to upgrade them M bushing. The bushings are cheap and the install is low for cost when doing a rear bar. You been warned if don’t replace the bushing the car will bounce around a lot and yu will not get good rear grip. There is two link in the rear you can also change to M link if you wish and they do matter a lot FWIW.

This setup will get you back to BMW OEM pitch which is a frequency of 12% higher at the rear than the front. The spring I selected is within the working v3 range.

The wheel spring rates are:

Front 215 lb/in (KW stock is 258 lb/in)
Rear 285 lb/in (KW stock is 205 lb/in)

In the mean time increase front rebound as much as you can...it is the only thing you can do.

How I got the info is much longer story……



I will PM you shortly.

Orb

Why the H&R rear bar over the UUC bar? Different stiffness? I thought the H&R bar was fixed where as the UUC is adjustable

EDIT: Thanks for all the input, I'm sure you have spent countless hours figuring this out.

[Orb]

Originally Posted by Humtek

Why the H&R rear bar over the UUC bar? Different stiffness? I thought the H&R bar was fixed where as the UUC is adjustable

EDIT: Thanks for all the input, I'm sure you have spent countless hours figuring this out.

The UUC bars work great if your car has stock springs. The numbers I gave in this thread are still not enough to bring the car around back OEM flat ride state so the rear is still a bit soft. The flat ride stat is when the suspension frequency in the rear is about 15% higher that the front. Every BMW has this and that is one reason why they feel great.

The rear motion ratio for this car is about 0.32 after being squared (it truly sucks). The problem with this is that when you have such a high motion ratio it is difficult to get a stiffer rear spring and damper to work and this is mostly due parasitic losses in the system so you have inconsistency in suspension action and this is a really a big deal!! I know the rear spring rate stated with the M bushing will be okay and maybe a bit more but the damper craps out around 900 lb/in the rear for adjustment as the adjustments go very non linear near the end. You can go higher with rear spring rates but you need some M link and a variation of my custom links as well. All the soft bushing and links must go.

If anyone thinks the spring are to stiff then you will realize they are not so do the math below and the wheel rate is what you feel and is the only thing that is important to you. The rear spring rate on the KW is 570 lb/in.

Coil spring rate x 0.32 = wheel spring rate
800 lb/in x 0.32 = 256 lb/in

Sorry about the error in my numbers in the previous post.

Orb

[JRZFresh]

Originally Posted by Laurence928

Hey Guys,

Supposedly, the AWD of the xi will disengage once the vehicle hits approx. 75 MPH, which may acount for one of the posts complaining about the xi not handling the way he felt an AWD should handle at high speeds.

Are you kidding??? How does that make any sense?? Why would BMW design a AWD system that disengages at a set speed?

[HERR FSTIR]

Originally Posted by JRZFresh

Are you kidding??? How does that make any sense?? Why would BMW design a AWD system that disengages at a set speed?

To reduce drivetrain losses. Supposedly the AWD system also reverts to "RWD mode" at very low speeds to assist in parking lot maneuvers and so forth.

Back to the major topic - I would be curious to know if Orb has an xdrive or a RWD 335 (I suspect the latter). He clearly knows a great deal about the suspension setup, and has put a lot of time into making improvements. I am just curious whether his comments specifically relate to the xi suspension problems or pertain to the 3 series in general.

[Orb]

Originally Posted by HERR FSTIR

To reduce drivetrain losses. Supposedly the AWD system also reverts to "RWD mode" at very low speeds to assist in parking lot maneuvers and so forth.

Back to the major topic - I would be curious to know if Orb has an xdrive or a RWD 335 (I suspect the latter). He clearly knows a great deal about the suspension setup, and has put a lot of time into making improvements. I am just curious whether his comments specifically relate to the xi suspension problems or pertain to the 3 series in general.

I have RWD with a Quaife.

The rear suspension are the same and the front is similar as well expect more mass and there slightly higher front frequency. The thing I am looking at is total load transfer for your car so the details on 2wd vs 4wd is not a significant issue but a consideratio. The purpose of this is to see the load distribution on each tire in a steady state roll which dictates car balance. The statement applies for 3 series in general including the M3.

Orb

[deletedelete]

Ive never heard of the awd disengaging at certain speeds. Where can I find out this info? Im sure it wasnt in the manual.

[NM_BMW]

Originally Posted by Prowess Symphony

Ive never heard of the awd disengaging at certain speeds. Where can I find out this info? Im sure it wasnt in the manual.

+1 I've never heard of it either. I always thought the XI was slower up top because of the driveline loss. If it disengaged at 75mph then it would be just as fast as the RWD 335.

[jgalaxy]

Originally Posted by Humtek

+1 I've never heard of it either. I always thought the XI was slower up top because of the driveline loss. If it disengaged at 75mph then it would be just as fast as the RWD 335.

I seriously doubt this claim too. I've taken the car to the track and seriously pushed the car between 50-120mph with traction control on and boys and girls it is on - there is no mistake. From a safety standpoint you would want to turn it off to eliminate the irrartic behavior at the edge.

[HERR FSTIR]

Whether xdrive disengages the front axle at speeds in excess of 100 mph has not been substantiated by any BMW technical document (to my knowledge). However, this idea has been mentioned several times on e90post and it might be best to consider it an urban legend until somebody can provide credible documentation. Nonetheless, if true, the rationale would most likely be to prevent excessive drive train loss.

On the other hand, BMW's website does state that the clutch pack disengages at low speeds to improve maneuvering.

"when parking, the system reacts to the need for high manoeuvrability at low speed by opening the clutch completely so the powertrain functions optimally."

http://www.bmw.com/com/en/insights/t...icle=mm_xdrive


I recall reading somewhere that this occurs at speeds <10mph. Unfortunately I can't remember the source.

[deletedelete]

Originally Posted by HERR FSTIR

Whether xdrive disengages the front axle at speeds in excess of 100 mph has not been substantiated by any BMW technical document (to my knowledge). However, this idea has been mentioned several times on e90post and it might be best to consider it an urban legend until somebody can provide credible documentation. Nonetheless, if true, the rationale would most likely be to prevent excessive drive train loss.

On the other hand, BMW's website does state that the clutch pack disengages at low speeds to improve maneuvering.

"when parking, the system reacts to the need for high manoeuvrability at low speed by opening the clutch completely so the powertrain functions optimally."

http://www.bmw.com/com/en/insights/t...icle=mm_xdrive


I recall reading somewhere that this occurs at speeds <10mph. Unfortunately I can't remember the source.

Yup, the article doesnt say anywhere that it turns off a high speeds. The article even mentions driving around corners fast and feeling the grip of the xDrive. Im sure BMW would have mention somewhere if the awd turns off at any point.

With all techs and tuners around here, Im surprised no one has proved or disproved this yet.

[Xi021]

you know, i have an '06 325xi and i think it handles fairly well. i mean ya, its nothing compared to any of the M classes, but its not as bad as people want to make it sound. it "feels" more floaty and like it can't take the hard turns, but i've done on ramps at 55 in 4th and though it kinda feels like i'm unstable (the body roll) but i know all 4 wheels are on the ground and keeping me in line. the suspension isn't great but its not at as bad as people want to make it seem. also, i've gotten up to 130mph on the highway and again, it feels floaty but perfectly maneuverable. ive had zero problems switching lanes and such at high speeds. (then again i'm used to driving a 4runner that is highly unstable at speeds over 60)... i do agree that it should not feel like its going to explode when i go over a speed bump though :\ .... i've never read about the xdrive disengaging, but i do know that its normally kept at 40-60 split. so most of the power is going to the rear wheels

[J.P.]

Dinan now makes a full stage 3 suspension for the xdrive cars.

Anyone try these yet?

[wakeboarder109]

Originally Posted by JP_335xi

Dinan now makes a full stage 3 suspension for the xdrive cars.

Anyone try these yet?

I'm very interested to know this as well

[NM_BMW]

What does the kit consist of ?

EDIT: Nvm, just camber plates.

[Hampi]

http://www.dinancars.com/store/produ...cat=321&page=1

@Orb: What do you think of this solution?