# 540i sway bar set up M5 front Dinan Rear



## s500fun (Sep 30, 2003)

Just want to know how people feel about this set up with the stock sport suspension for a 1998 bmw 540i let me know what you think and if I should go ahead with it ~ Suman


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## SoonerPast (May 14, 2002)

*My setup, long response*

For my 540, Eibach springs, Koni shocks/struts, M5 sway bar front and rear.

I will be at a track for the first time since the installation this weekend. On the street the difference is noticeable, mostly because the car is lower and it scrapes in places it would not have before.

The nice part of the Koni choice is adjustability, but really only on the front. At the tighter settings, the difference is very significant. It is uncomfortable for street and interstate driving. At the lightest setting they aren't much different than BMW stock.

I expect significant track performance improvement with the setup. The car is lower and the camber is slightly more negative.

If I were doing it again, I would consider keeping the stock BMW sport springs. It is such a big job to get to the mounting locations for the shocks that it seemed silly not to change the springs while we were there.

The larger sway bars alone will make a big improvement in handling. You already know the front change is a big job and that is an understatement. I intend to keep my car a long time and I enjoy taking it to the track. The swaybar improvement really helps the car handle like a much smaller car.

Now, more power would be nice. I have visions of a stripped down E39 trackmobile in a couple of years.


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## Malachi (Sep 30, 2003)

s500fun said:


> Just want to know how people feel about this set up with the stock sport suspension for a 1998 bmw 540i let me know what you think and if I should go ahead with it ~ Suman


I don't know how the M5 front differs from the Dinan, but I have to say that the Dinan sway bars made a significant difference in handling..much less body role and understeer. I also had driven on a road coarse while it was OEM then after and again big difference. It is my favorite mod.


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## DZeckhausen (Mar 11, 2003)

s500fun said:


> Just want to know how people feel about this set up with the stock sport suspension for a 1998 bmw 540i let me know what you think and if I should go ahead with it ~ Suman


That's exactly the set-up I have on my 2001 540i/6 and it works very well. I have the Dinan rear bar in the middle setting.

It's interesting that the Dinan and the M5 front swaybars are the same diameter and the Stage 3 kit for the M5 does NOT include a new front swaybar. That tells me that Dinan considers the M5 front bar to be good enough. The M5 bar is certainly cheaper than the Dinan front 540i bar. The M5 bar is less than $100.

I wrote up detailed instructions for doing the swap yourself after doing my own and then my neighbor's car. 
http://www.zeckhausen.com/howto/bmwe39/swaybar_replacement.htm


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## Malachi (Sep 30, 2003)

DZeckhausen said:


> I have the Dinan rear bar in the middle setting.
> 
> It's interesting that the Dinan and the M5 front swaybars are the same diameter and the Stage 3 kit for the M5 does NOT include a new front swaybar. That tells me that Dinan considers the M5 front bar to be good enough. The M5 bar is certainly cheaper than the Dinan front 540i bar. The M5 bar is less than $100.


Great info Dave :thumbup: I have my Dinan rear sway bar also set in the middle.


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## DZeckhausen (Mar 11, 2003)

Malachi said:


> Great info Dave :thumbup: I have my Dinan rear sway bar also set in the middle.


What's that I see in the foreground of your photo? Could it be a stock rubber brake line? :tsk:


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## Malachi (Sep 30, 2003)

DZeckhausen said:


> What's that I see in the foreground of your photo? Could it be a stock rubber brake line? :tsk:


 :rofl: :rofl: :rofl: 
Yes, :eeps:


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## Lscman (Aug 5, 2003)

Soonerpast,

Did you happen to compare the free length of the BMW Sport and Eibach springs?? Which is shorter? Would you mind measuring the free length of your front and rear Sports? I am trying to figure out the difference between them. I am surprised with your assessment about ride height dropping. Many folks have posted ride heights with Eibach and Koni that are within 1/4" of my BMW Sport setup. My car sits around 14" from fender lip to the center of the wheel cap.


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## SoonerPast (May 14, 2002)

In a very rudimentary way, by placing the BMW and Eibach springs on the floor side by side, the Eibach were slightly taller than the BMW sport, but less than 1/2 inch. I am no pro at this stuff. I thought that since the Eibach are "progressive", that explained them being taller.
After installation the car did drop a small amount. On the RF board, Viestb has collected various measurements and mine are included there.


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## s500fun (Sep 30, 2003)

Just did the instal using Dave Z.'s directions. With a lift I cut the time to 1 1/2 for the front and 10 seconds for the rear haha. What a difference the car changed from night to day. The handling on the highway was exceptional. First thinbg I did was hit 140 in and out of traffic wooo what a rush it feel like my old E36 M3 Well good luck everyone else that thinking of this mod ~Suman 1998 540i sport


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## Lscman (Aug 5, 2003)

Soonerpast,

Vietsb's static ride height data is nice for those interested in changing "looks", but it has no bearing whatsoever on handling or spring rates. We need spring wire diameter and coil count and a couple other things to properly evaluate each spring for track use. It is terribly unfortunate that so many folks are throwing springs on their cars without expected performance results or being able to predict the outcome. Sounds like another set has been installed without collecting this data (geez).

Anyway....the bit of information you provide is very interesting! If the Eibach springs are, in fact, slightly taller uncompressed and slightly shorter compressed, that tells us one thing....they collapse farther under load. Therefore, they are a lower lb/in spring rate than the stock spring (softer than stock). This is a very depressing fact for me to swallow, since I was considering these springs. Perhaps Eibach softened the front and stiffened the rear to provide less understeer?? How do the lengths of the Eibach and stock rear springs compare?? I hope you ccompared both front and rear heights & I assume you were talking about the fronts.

The front H&R sport for sport spring is much shorter than the Eibach which tells me it's stiffer. It is difficualt to compare accurately since the H&R loaded ride height is lower too. The H&R rears are terrible for track because they are highly progressive. They get super stiff when compressed about 1" below ride height. This ramps up loads on the outside tire in corners. If you like a tailhappy condition like a Mustang, perhaps they are suitable.

The Eibach's for the E39 are not significantly progressive. The coils are equally spaced except for the end of spring pigtails. IMO, that's the last thing you'd want for track anyway.


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## DZeckhausen (Mar 11, 2003)

s500fun said:


> Just did the instal using Dave Z.'s directions. With a lift I cut the time to 1 1/2 for the front and 10 seconds for the rear haha. What a difference the car changed from night to day. The handling on the highway was exceptional. First thinbg I did was hit 140 in and out of traffic wooo what a rush it feel like my old E36 M3 Well good luck everyone else that thinking of this mod ~Suman 1998 540i sport


One and one half hours? That's great! I'll add that little detail to the web page. Were you working by yourself, or were there two of you? What did you use to lift the motor? A tranny jack?

Isn't the difference amazing? I love it! Did you put in a rear M5 bar or a Dinan bar?


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## s500fun (Sep 30, 2003)

*540i with new sway bars*

Dave_

The set up kiss a$$ I love it. Actually I had my mechanic put the front one on. He did it by himself in no time. This dude is a genius and charged me 100 bucks. Could not say no!!!

P.S- please dont ask me where I can put you in contact with him cause I assure the price will not me the same 

The directions were solid and well written. I think the fact that my car is pre 1999 I had it easy. The fact I did not have xenon lights saved alot of trouble. The fact that a lift was involved made it way easier to take the bar out. Well I hope to see you soon, need those rotors.

~Suman


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## Ohmess (May 29, 2003)

Lscman said:


> Soonerpast,
> 
> Vietsb's static ride height data is nice for those interested in changing "looks", but it has no bearing whatsoever on handling or spring rates. We need spring wire diameter and coil count and a couple other things to properly evaluate each spring for track use. It is terribly unfortunate that so many folks are throwing springs on their cars without expected performance results or being able to predict the outcome. Sounds like another set has been installed without collecting this data (geez).
> 
> ...


I'm confused.  How can you tell the characteristics of a spring by its wire diameter and coil count? Don't the properties of the metal/alloys used to make the spring and the process whereby the spring is manufactured and finished have something to do with the spring's characteristics? :dunno: I guess I'm wondering why its possible to determine a spring's characteristics by physical observation?


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## Lscman (Aug 5, 2003)

Spring coil wire used for automotive springs has fairly similar characteristics from one manufacturer to another. The differences in spring stiffness for a particular diameter wire are typically on the order of 5%. There are good formulae that predict spring rates and allow you to compare them within a few percent.

http://www.m5board.com/vbulletin/showthread.php?s=&threadid=35113
http://www.m5board.com/vbulletin/showthread.php?s=&threadid=35313
http://www.m5board.com/vbulletin/showthread.php?s=&threadid=35075

From a subjective viewpoint, a person can also accurately "compare" spring rates by comparing ride height and free length.

For example, if an Eibach Pro-Kit 5 series spring free length is longer than a stock sport spring but the ride height is lower, this means the Eibach spring has a lower spring rate. The car's fixed weight compresses the spring farther (more inches) than stock. In fact, this IS the case.

There are many other properties that you can accurately predict and determine by physical observation. For example, the H&R "sport for sport" 540i rear spring is extremely progressive. About 1/3 of it's length is comprised of tightly wound coils that go into coil bind when the suspension is compressed about 1". When this happens, the spring rate suddenly increases about 50%. On a "slammed" suspension where the jounce travel is very low, this is cool as heck because it allows a streetable, supple ride on smoother surfaces while preventing bumpstop contact on a rough road or a sharp turn. From a performance perspective, they totally stink. When the spring rate jumps as the car roll angle changes, the tires lose grip and traction loss is encouraged almost like hitting bumpstops. This can send you into the gravel trap or guiderail. Racers can not maintain max G's at the limit with a progressive spring. To make matters worse, a progressive rate spring literally jacks the car up in turns. The outer spring rate rises when it compresses and the inner spring rate drops which physically lifts the car!

I am trying to determine the aftermarket options for 5 series E39 cars. Watching folks "try" springs with secret characteristics is very frustrating....especially when somebody removes a sport spring and installs an even softer spring in hopes of improving handling. With regular and sport BMW offerings, the aftermarket choices are ambiguous. What a friggin' waste of time to "try" a spring not knowing the outcome. There are slim pickin's for these cars & the 5 series community needs to be able to intelligently choose the proper spring for their needs.

Hope this helps


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## SoonerPast (May 14, 2002)

I agree that the spring decision is difficult. I chose Eibach on the strength of a mechanic's suggestion. He asked what I was attempting to achieve and made his recommendation.

I have now been to the track on the new setup and the car does handle better for me. I am happier with its dynamics and it is a lot more fun to drive. With adjustable Koni's, I can return to a more civilized road car for everyday needs.


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