[exidisjon]

Originally Posted by Prowess Symphony

I thought the kw v3 was replacing the front/rear struts?

kw v3 seem to be what everyone says but im still gonna go with the less expensive stuff first. And others have said that sways were not something that should be done. Seems to be lots of conflicting stuff about the xi still.

Yea what i meant was thats the most problems xi's have or what i feel is bothering me the most.

When you go thru high speed and make a hard lane change the body roll is too much.. Getting the kw v3 or M3 struts/sways cure most of the body roll..

Also kwv3 with 19's look dam good since there isnt any wheel gaps.

Im going for the kwv3 soon but not sure how soon.. Maybe possibly never..But i might be getting struts for cheap nearby so might give them a try.

[deletedelete]

Originally Posted by exidisjon

Yea what i meant was thats the most problems xi's have or what i feel is bothering me the most.

When you go thru high speed and make a hard lane change the body roll is too much.. Getting the kw v3 or M3 struts/sways cure most of the body roll..

Also kwv3 with 19's look dam good since there isnt any wheel gaps.

Im going for the kwv3 soon but not sure how soon.. Maybe possibly never..But i might be getting struts for cheap nearby so might give them a try.

Oh cool. I didnt know the m3 struts fit. Thanks

[Orb]

Originally Posted by Prowess Symphony

Thanks for the advice. So the m front bar and bushing/clamp is something I can add to the list? Ive heard that sway bars in either the front or rear imbalance the xi and should be left stock.

When it comes to balance between a 2wd vs 4wd the setup is much the same. The stock front bar with the M3 rear bar will give close to the same balance as M3 but biased towards understeer with the KW because of the slightly softer rear spring. It should feel peaty good with this combo right up to limit and then understeer a bit. No doubt it will be far better than the stock car. This is the best possible solution that I can see other than ramping up the rear spring a lot to work wit the stiffer front bar. We only have some many options to select from and this would be a good one.

The problem with the UUC and H&R bar they work real good with the sock spring rates but the after market stuff tends stiffen the front and soften the rear spring and then those bars start throwing the balance off towards understeer with other issue as well. The bars have such huge effect that you really got watch what you pick.

I suggested the front M3 bar bushing to match the rear. They are very stiff. This will ensure you keep thing matched as the stock bushing are considerably softer. The bar takes a fair bit out of body roll a well and you give up 0.2 degrees less body roll if you had a 27 mm front bar. It is a good compromise.

The roll bar selection is up to you but since you had a rear M3 bar listed I commented.

Orb

[Orb]

Originally Posted by exidisjon

KW v3 and front and rear struts& sways cure *most of xi's problem....I driven a friends car who had those mods with a tune and the difference is nite and day....After driving his car and coming back to mine which is all stock with just tune and car felt less agressive and SHITLOAD of bodyroll is what you really notice....With the KWv3 the bodyroll was pretty much gone and steering response is alot better as well...

The roll is still there but the rate of roll is reduced. The KW spring stiffness will not do a hell of lot for reducing roll but it feels better which is important.

The car will understeer abit more with KW if no correction is taken but this goes with amost every after market kit out there right now. You got to do skid pad in parking lot to notice for most of you.

Orb

[Kev]

Originally Posted by Orb

The roll is still there but the rate of roll is reduced. The KW spring stiffness will not do a hell of lot for reducing roll but it feels better which is important.

The car will understeer abit more with KW if no correction is taken but this goes with amost every after market kit out there right now. You got to do skid pad in parking lot to notice for most of you.

Orb

I notice that when I hit my exit at the Mass Pike (see arrow). It's a up hill almost full 360 degree right turn. In the past, I can feel the body roll even at 30 mph, but now I can take the same corner at up to 45-50 to feel the same body roll and understeering. Overall, it's better, but it's no where as good as an $1800 coilover kit should feel.

KW focused too much on getting the car dropped as much as possible and in the mean time sacrificed the handling aspect of the kit. There's nothing wrong with the struts, but the springs they chose are horrible. I'm trying to hit up my tuner and see if they can find me some custom made linear springs to match up with the KW struts. I'm also taking out my UUC bars and replacing them with the stock front bar, M bushings, and the M rear bar, along with a bunch of rear M suspension upgrades, plus the M3 front strut tower brace. All thanks to Orb's pointers

It's too bad that us XI owners can't benefit from the front suspension upgrades.

[Orb]

Originally Posted by Kev

I notice that when I hit my exit at the Mass Pike (see arrow). It's a up hill almost full 360 degree right turn. In the past, I can feel the body roll even at 30 mph, but now I can take the same corner at up to 45-50 to feel the same body roll and understeering. Overall, it's better, but it's no where as good as an $1800 coilover kit should feel.

KW focused too much on getting the car dropped as much as possible and in the mean time sacrificed the handling aspect of the kit. There's nothing wrong with the struts, but the springs they chose are horrible. I'm trying to hit up my tuner and see if they can find me some custom made linear springs to match up with the KW struts. I'm also taking out my UUC bars and replacing them with the stock front bar, M bushings, and the M rear bar, along with a bunch of rear M suspension upgrades, plus the M3 front strut tower brace. All thanks to Orb's pointers

It's too bad that us XI owners can't benefit from the front suspension upgrades.

I know you want more performance more than v3 can offer which is possible. When we look at bar selection with higher spring rate we want to change the frequency biasing to the front more than the BMW biasing and it just doesn’t want to work. If we could pick bars of our choosing it would be 26 mm solid front bar and 20 mm solid rear bar…that 1 mm extra in the front is huge in stiffness. We are fighting an up hill battle with the high motion ratio in the rear but it is achievable for higher spring rates. The rear m3 bar is ideal but we lose some roll and camber control as well. The M3 bar seems to best possible lowest cost solution with stiffer springs. Although we increased roll with the smaller roll bar will gain most of this back with stiffer bushings so it may be a wash. You be surprised how much roll those bushing induce.

Kev, get rid of the front bar and put the stock one back on and test for few days. Understeer should reduce a fair amount. This is an easy test which is cheap to do. I'm assuming you have UUC rear bar.

I have given up on the pipe dream of running the H&R bar as well. I know I can do it but it is not want I really wanted. I looked into tooling a new roll bar and that will cost about 5000.00 and another 2500.00 to forge the ends for low production run.

I did get all the part numbers for you so look for some info tomorrow. Don’t hesitate to PM for a response.

You can check HP Motorwerks for new M3 stuff that has been validated and there should be more to come. The two most important rear links will be listed shortly.

If have any comments you can contact a KW rep on the board Glen@KW I think he would like to hear from you all if your not satisfied with an end solution. He wants to improve the product so if you say noting then it doesn’t get better.

Orb

[sparkyg]

Good stuff as always Orb. Dam I think you've forgotten more about suspension than I know

[Orb]

Kev, check your PM......

If anyone wants to help themselves I do need information on the weight on the unsprung mass of the front suspension. You simply need to take out the bolts that hold the strut to the tower and let the front well drop as low as possible on bath room scale. Please take several reading and then make them all down.

I would also appreciate if any one can list of the specification for xi including front to rear weight distribution. I got some data but I like it form a good source.

I will add this to load transfer worksheet and I will give you some baseline numbers on how to balances the car and lot more. If you work as group then you get some information how to setup the car rather than guessing.

I don’t have this car and to busy to do this. Post information in this thread if anyone wishes to help.

Orb

[vinny84]

On BMW's site they state the weight distribution:

front 53.8%/rear 46.2% - manual
front 53.9%/rear 46.1% - automatic

[Orb]

Here are some base calculation for load transfer. It is not 100% accurate until verified so I made a few assumption but they are reasonable. Do not take this as prefect by any means. The magic number is phrase coined by some race car engineer but it means balanced in this range. This is at 1 G in corner

There results are based on the information I gave Kev.

Orb

[Septro]

Is there a summary version of what M3 suspension parts can be used on a 335xi?? I tried following the thread but too much conflicting and incomplete information makes purchasing the right products difficult to tighten up the XI suspension.

[Xi021]

Originally Posted by Nick Nazareno

OP, (ie they lean a lot during cornering) but they have excellent wheel control (ie wheels follow the pavement and absorb bumps very well)

just because a car is leaning doesn't mean it can't carry a substantial amount of speed through a corner. Also, cars with 'more lean' typically have more compliance which makes the car handle mid corner bumps much easier. Also, part of what you are experience is the increased mass that comes with driving a large, heavy AWD car

I've seen many owners 'upgrade' to an expensive adjustable suspension, dial up the firmness and have a car that feels great (doesn't lean) but handles awful (too stiff, corner weights wrong, etc). not the best use of $$$$ in my opinion

This (see above) seems to make sense... does anyone else have the same feeling? i just got an 06 325xi (all i can afford haha) and it seems to do great in the turns even if it doesn't feel tight.

also, i would like to know if anyone has any good ideas on how to enhance acceleration... this is my first "real" car (coming off a '96 4Runner) and i'd like to make it a little quicker.

thanks

[GmanJeff]

I also tend to think Nick is on to something here. I would be surprised to learn that BMW carefully designed, engineered, and tested their AWD cars to build in subpar performance. Of course, "feel" is entirely subjective, but it would indeed be interesting to see if the factory set-up objectively allows the car to get around a wet or dry course/route faster, or handle more safely in an emergency, as is.

[bulldog52]

Can anyone explain this - the guy with the 325xi talks about his car performing well in the turns and I know what he means. I have an 07 328xi sedan and an 08 335xi coupe. The sedan drives like it is on rails compared to the coupe - neither have any modifications. Why would there be such a big difference? There has to be an engineering explaination. Also, if you are wondering why I got the coupe if it drives so poorly - it is because I ordered it pre-production and never got to drive it before buying. I assumed it could only be better than a year earlier car with a smaller engine. Big mistake.

[Xi021]

haha i love the way you assume that i'm a guy... i would think that it has something to do with the weight distribution. those 2 extra doors on the e90 add alot of weight that had to be put somewhere... i'll look that up

[Xi021]

o and how do you make it so that you get email notifications when you get replys on a thread?

[equ]

Originally Posted by bulldog52

Can anyone explain this - the guy with the 325xi talks about his car performing well in the turns and I know what he means. I have an 07 328xi sedan and an 08 335xi coupe. The sedan drives like it is on rails compared to the coupe - neither have any modifications. Why would there be such a big difference? There has to be an engineering explaination. Also, if you are wondering why I got the coupe if it drives so poorly - it is because I ordered it pre-production and never got to drive it before buying. I assumed it could only be better than a year earlier car with a smaller engine. Big mistake.

They *should* have the same/extremely similar suspension. The difference is most likely tires, extra power of the turbo engine causing higher cornering speeds or less likely but possible, the extra weight up front with the N54.

[TayF80]

Does the front to rear sway bar ratio matter? like 32mm on front and 16mm on rear? or 27mm to 20mm? I am lookin to purchase sway bars soon

[louie_perm]

Originally Posted by TayE90

Does the front to rear sway bar ratio matter? like 32mm on front and 16mm on rear? or 27mm to 20mm? I am lookin to purchase sway bars soon

Much of the discussion is about exactly this issue.


Let me see if I am following with respect to Orb's Xi suggestions for those of us with the KW's:

- The KW V3's should mean an improvement in the rate of body roll, but they will cause a slight bias toward understeer at the limit due to the relatively softer rear springs.

- The stock front and (possibly) rear bars should be kept in place because aftermarket bar kits tend to stiffen the front relative to the rear, which is exactly the opposite of what the car needs.

- The M3 rear bar, being smaller than the stock rear bar, is possibly a better match for the softer rear springs.

- The M3 front and rear bushings should help--the rear is likely more important, but the front might be needed for balance if using the rear bushings.

- Stiffer springs in the rear are likely the only real way to re-acquire the "BMW" balance.

- A smaller 26mm bar in front would help but is not available.

Am I following? Not sure about the M3 stuff.

[TayF80]

I have been reading the threads. I still dont know if i should get front and rear sway bars, or just a front sway bar.

[louie_perm]

Originally Posted by TayE90

I have been reading the threads. I still dont know if i should get front and rear sway bars, or just a front sway bar.

The ratio absolutely matters. I'm still figuring out the specifics of how.

Best I can tell, if you're not replacing the stock springs, then I'm not sure it makes sense to change the bars. If you are changing the springs, then the specifics of the new springs are needed to determine if a sway bar (or other part) change is in order.

[Nikolas]

Originally Posted by louie_perm

Much of the discussion is about exactly this issue.


Let me see if I am following with respect to Orb's Xi suggestions for those of us with the KW's:

- The KW V3's should mean an improvement in the rate of body roll, but they will cause a slight bias toward understeer at the limit due to the relatively softer rear springs.

- The stock front and (possibly) rear bars should be kept in place because aftermarket bar kits tend to stiffen the front relative to the rear, which is exactly the opposite of what the car needs.

- The M3 rear bar, being smaller than the stock rear bar, is possibly a better match for the softer rear springs.

- The M3 front and rear bushings should help--the rear is likely more important, but the front might be needed for balance if using the rear bushings.

- Stiffer springs in the rear are likely the only real way to re-acquire the "BMW" balance.

- A smaller 26mm bar in front would help but is not available.

Am I following? Not sure about the M3 stuff.

There are many Autocrossers out there that would disagree with the concept of not stiffening the front to help reduce understeer. With my old STI I first tried the route of upgrading the rear bar only. While this helped a little, what really changed the dynamics of the car and made it very neutral was the addition of a much larger FSB - 29mm. It allows for more dynamic camber increasing the contact patch on the front tires through the turn allowing the rear tires to come around more freely.