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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Suspension | Brakes | Chassis > m3 sway bar and bushings



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      02-22-2012, 02:52 PM   #1
Sam335ix
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m3 sway bar and bushings

I was looking online and found these, wanted to make sure that these the ones I need to be getting for a 2011 335 xdrive sedan:

http://www.trademotion.com/partlocat...catalogid=4462
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      02-22-2012, 03:14 PM   #2
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That is the e93 rear bar. I'd try to find the e90/92 rear bar kit.

Call Tischer and I'm sure they'll hook you up.
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      02-22-2012, 03:18 PM   #3
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Hey Doyle

That is what Tischer sent me by email, did you see the drop down box where it says e9x option? Would that be it?
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      02-22-2012, 04:37 PM   #4
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Yup. That would be it. I didn't see that on the phone!
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      02-22-2012, 05:50 PM   #5
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Quote:
Originally Posted by Doyle View Post
Yup. That would be it. I didn't see that on the phone!
Thank you Doyle
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      02-22-2012, 07:13 PM   #6
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You are better off adding a larger front bar(aftermarket) than a larger oem rear bar. Although you have x-drive traction is still an issue adding a larger rear bar.
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      02-22-2012, 07:20 PM   #7
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Originally Posted by HP Autowerks View Post
You are better off adding a larger front bar(aftermarket) than a larger oem rear bar. Although you have x-drive traction is still an issue adding a larger rear bar.
Harold

You have been very helpful man and I appreciate it. So forget the read sway and just go with the front? I keep reading posts in here that the rear sway bar and bushings made a huge difference... can you explain why just opting for the front is better than the rear?

Thanks
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      02-22-2012, 07:37 PM   #8
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Quote:
Originally Posted by Sam335ix View Post
Harold

You have been very helpful man and I appreciate it. So forget the read sway and just go with the front? I keep reading posts in here that the rear sway bar and bushings made a huge difference... can you explain why just opting for the front is better than the rear?

Thanks
A sway bar works by pushing down on one wheel or pulling up on another. With the larger rear bar and the car going through a turn, the inside rear tire will be lifted up by the bar and have less traction.
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      02-22-2012, 07:40 PM   #9
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yeah so doesnt that mean adding just a rear bar will make the car oversteer? thats what i want. i hate the understeer on the x-drive


The of the major function of sway bars is to tune the handling balance of a car. Understeer or oversteer behavior can be tuned out by changing the proportion of the total roll stiffness that comes from the front and rear axles. Increasing the proportion of roll stiffness at the front will increase the proportion of the total load transfer that the front axle reacts and decrease the proportion that the rear axle reacts. In general this will cause the outer front wheel to run at a comparatively higher slip angle, and the outer rear wheel to run at a comparatively lower slip angle, which is an understeer effect. Increasing the proportion of roll stiffness at the rear axle will have the opposite effect and decrease understeer
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      02-22-2012, 07:41 PM   #10
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i have an e92 335xi. i want to get an m3 rear sway bar. should i get the M3 e92 rear sway bar? or the rear sway bar from the e93 M3?


OEM BMW E9X M3 Rear Sway Bar Kit. E9x M3 Kit includes rear 20mm swaybar, bushings, and brackets. E93 M3 Convertible Kit includes 23.6mm rear swaybar, bushings, and brackets. **Use of this kit on non E9x M3's is at your own risk.
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      02-22-2012, 07:59 PM   #11
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Quote:
Originally Posted by HP Autowerks View Post
A sway bar works by pushing down on one wheel or pulling up on another. With the larger rear bar and the car going through a turn, the inside rear tire will be lifted up by the bar and have less traction.
Thanks Harold, do you sell the front sway for the 335x drive sedan 2011? Would it be an over kill to do a front and rear sway? The fact that I am not going to go with an LSD, does it make much sense to do the rear at all then?

Last edited by Sam335ix; 02-22-2012 at 08:06 PM.
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      02-22-2012, 08:30 PM   #12
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Quote:
Originally Posted by Sam335ix View Post
Harold

You have been very helpful man and I appreciate it. So forget the read sway and just go with the front? I keep reading posts in here that the rear sway bar and bushings made a huge difference... can you explain why just opting for the front is better than the rear?

Thanks
Harold knows his stuff. Here is the long answer from The HACK.



"I'm going to let you in on a little secret. "Understeer" as a term is too often used to describe the wrong things. I'm going to let you in on another secret. Suspension tuning is all about a series of compromises, and each compromise will have different effect on how the suspension will actually behave depending on what other components are "upgraded." The last secret I'm going to let you in on, is that 99.9% of the people posting on these forums will never take the car to the track where they experience actual understeer to actually be able to give you any sort of objective answer as to what mod actually affect the balance of the car, and likely will not know understeer even if it bit them in the ass.

Now that I got the pleasantries out of the way. The reason why BMW front suspension typically employs a thicker front anti-roll bar is because of the MacPherson strut design. Unlike double wishbone type suspension, the MacPherson strut has an unfavorable camber curve, in that the camber does not increase linearly as the suspension is compressed. So as the car takes a corner and sets, the outside suspension is going to compress past the roll center and will go from a favorable increase in negative camber to start to lose the negative camber. When that happens the front end will lose grip rapidly. One of the solutions to alleviate this problem, is to deploy thicker front anti-roll bars to prevent the outside suspension component from compressing PAST the roll center and start to lose camber. It's a way to artificially increase spring rate to one side of the suspension without giving up straight line ride comfort. You'll find that most balanced chassis with double a-arm or double wishbone suspension front and rear will likely have very similar anti-roll bars front and back. A great example is the 1991 Acura NSX, the front and the rear anti-roll bars are within a MM in diameter and the NSX-S (JDM versions) actually has thicker rear anti-roll bars. In 1993 they increased the front swaybars to remove grip up front and promote "understeer" since the early NSXes were deemed too tail happy (i.e. NEUTRAL) for 99.95% of your average drivers.

But the entire system needs to be taken into consideration, since the amount of spring compression on the outside is going to depend on a lot of different factors. Meaning going toO thick on the swaybar will result in the front end not compressing enough, therefore not getting enough grip when entering corners, resulting in corner entry understeer. However said thicker swaybar may actually REDUCE corner exit understeer since it will retain a higher spring rate up front and potentially keep the front tires on the ground longer when accelerating out of a corner.

All of this, is assuming you're already taking the ideal line through a specific turn. If you're EARLY into a turn, or carrying too much speed into the turn, you are going to UNDERSTEER regardless. Most of the so-called journalists who mention "understeer" as a problem on these cars are usually talking about corner exit understeer, whereby when you apply too much throttle the car will tend to push at the exit of a turn rather than have the rear end break loose.

Now, if you want to talk about how to actually fix understeer in this particular instance, I've pointed out multiple times that the best way to actually fix it is by fixing the driver first. But in case you don't actually plan to do this part (fixing the driver), there are things on this particular chassis that you can do that may actually alleviate corner exit understeer. One of the biggest problem it has, believe it or not, is the fact that it lacks a mechanical limited slip differential. On a car with LSD, upon corner exit understeer when it doesn't respond to MOAR throttle, an LSD will actually attempt to send power to the outside wheel rather than inside wheel to attempt to correct it, and eventually too much power WILL overwhelm both rear wheels and switch it from understeer to oversteer. So if adding grip via driver/tire/camber/whatever is not an option, adding an LSD will go a very long way. But a simulated LSD via braking the wheel that is slipping will not."
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      02-22-2012, 08:39 PM   #13
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I just read your post in another thread, it makes total sense and I 100% agree that most drivers dont know unders steer and the term is used very losely. What I want is an over all better handling of my x drive, once its dropped I guess it will do some of the trick but it cant be the silver bullet. I have a 540i msports and the car handles like a beast and compared to the x drive its night and day. The more I read the more I get confused lol, at this point I think I am just going to drop the car for now and see how it handles and go from there.

I think an LSD and then rear m3 sway bars would become an option If I still have the floaty feeling after lowring the car.
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