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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Suspension | Brakes | Chassis > Upgrading front sway-bar only a bad idea?



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      02-28-2013, 12:10 AM   #1
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Upgrading front sway-bar only a bad idea?

I was going to do front and rear M3 sway bars but really don't want to drop the rear subframe again (just did it a week ago) to do the rear, can I just upgrade the front swaybar or will this throw my car out of balance? I honestly can't see to much improvement with a upgraded sway bar in the back (have a pretty stiff rear suspension with mods I added last week) but maybe a bit in the front.

Here is the sway bar I want to get (want to do M3 since everything else is lol!)

http://hpashop.com/BMW-OEM-M3-Front-...bar-e9x-m3.htm
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      02-28-2013, 12:20 AM   #2
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There's not much of a benefit to roll in the front of the car. Adding the M3 front sway will help curb that behavior. It won't be a night and day difference, but you'll notice. Go for it!
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      02-28-2013, 12:23 AM   #3
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Quote:
Originally Posted by CJ421 View Post
There's not much of a benefit to roll in the front of the car. Adding the M3 front sway will noticeably curb body roll - go for it!
You mean no benefit to back but benefit to front...I was thinking the same....appears the damn M3 swaybar bar is on national back order until April. I saw one for sale for a E92....I assume this would be the same for a E90?
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      02-28-2013, 12:38 AM   #4
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Yeah the front will turn in flatter w/ the front sway - it's just adding to the total effective spring rate up there by transferring forces from one side of the car to the other.
I see you already have coilovers so that should be plenty of stiffness in the rear. No need for rear sway; just apply throttle to rotate the rear.

The sway bars aren't differently designed between E9x variants, so one from an E90 will fit fine. The E93 M3 sway bar is a bit more powerful, you could try that.
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      02-28-2013, 12:59 AM   #5
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Quote:
Originally Posted by CJ421 View Post
Yeah the front will turn in flatter w/ the front sway - it's just adding to the total effective spring rate up there by transferring forces from one side of the car to the other.
I see you already have coilovers so that should be plenty of stiffness in the rear. No need for rear sway; just apply throttle to rotate the rear.

The sway bars aren't differently designed between E9x variants, so one from an E90 will fit fine. The E93 M3 sway bar is a bit more powerful, you could try that.
What he said!
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      02-28-2013, 01:05 AM   #6
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Quote:
Originally Posted by HP Autowerks View Post
What he said!
harold you have one I can get or are they on back order? I like ordering from you lol!! Also lengthening the endlinks in front was great advice...my buddy had shortened his and tried your way of lengthening them and it is much better
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      02-28-2013, 01:06 AM   #7
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Quote:
Originally Posted by CJ421 View Post
Yeah the front will turn in flatter w/ the front sway - it's just adding to the total effective spring rate up there by transferring forces from one side of the car to the other.
I see you already have coilovers so that should be plenty of stiffness in the rear. No need for rear sway; just apply throttle to rotate the rear.

The sway bars aren't differently designed between E9x variants, so one from an E90 will fit fine. The E93 M3 sway bar is a bit more powerful, you could try that.
Great post & info
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      02-28-2013, 01:09 AM   #8
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If you replace only the front bar with a beefier one you'll get more under steer than without the replacement bar. I'm not sure why you would want to do this. But then I guess it depends on what you are trying to accomplish. For me, I'm looking for better overall handling with less under steer. I've made my tire sizes more square and have added a camber plate from Dinan and gotten a significantly better handling car. I've also upgrade the bars but did so front and rear.
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      02-28-2013, 01:25 AM   #9
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Quote:
Originally Posted by HeelToe View Post
If you replace only the front bar with a beefier one you'll get more under steer than without the replacement bar. I'm not sure why you would want to do this. But then I guess it depends on what you are trying to accomplish. For me, I'm looking for better overall handling with less under steer. I've made my tire sizes more square and have added a camber plate from Dinan and gotten a significantly better handling car. I've also upgrade the bars but did so front and rear.
You would think that, but in the BMW's the opposite is true. You get much better turn-in, less understeer and less body roll.
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      03-03-2013, 11:44 PM   #10
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Quote:
Originally Posted by HP Autowerks View Post
You would think that, but in the BMW's the opposite is true. You get much better turn-in, less understeer and less body roll.
Gotta help me on this one. The physics don't change by brand. If what you are saying is true then help explain further.
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      03-04-2013, 01:21 AM   #11
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Quote:
Originally Posted by HeelToe View Post
Gotta help me on this one. The physics don't change by brand. If what you are saying is true then help explain further.
MacPherson Strut.

Typical "race car" geometry would dictate, yes, thicker front bar would result in less grip up front thus increasing a chassis's tendency to understeer. But the MacPherson type strut design has unfavorable camber gain once the suspension compress past roll center. Therefore, on a car with limited camber, preventing additional roll increase in the front MIGHT actually improve grip in the front rather than take it away.

HAVING SAID THAT. You can't just throw thicker front bar and assume it'll reduce understeer. It has to be a combination of factors, one mainly of reducing the suspension's compression past roll center. If you have a very stiff suspension, with moderate amount of camber, the result will likely be positive. If you have a soft-ish suspension and factory camber, the problem might actually be exacerbated. If you have any combination there of, or if the vehcile's lowered significantly, the result then become a little bit less predictable.
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      03-04-2013, 02:03 AM   #12
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Quote:
Originally Posted by The HACK View Post
MacPherson Strut.

Typical "race car" geometry would dictate, yes, thicker front bar would result in less grip up front thus increasing a chassis's tendency to understeer. But the MacPherson type strut design has unfavorable camber gain once the suspension compress past roll center. Therefore, on a car with limited camber, preventing additional roll increase in the front MIGHT actually improve grip in the front rather than take it away.

HAVING SAID THAT. You can't just throw thicker front bar and assume it'll reduce understeer. It has to be a combination of factors, one mainly of reducing the suspension's compression past roll center. If you have a very stiff suspension, with moderate amount of camber, the result will likely be positive. If you have a soft-ish suspension and factory camber, the problem might actually be exacerbated. If you have any combination there of, or if the vehcile's lowered significantly, the result then become a little bit less predictable.
great post! I have all M3 upper/lower control arms, Meyle HD tie-rods & coil-overs so my suspension is very stiff. .... so this should work well.
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      03-06-2013, 08:37 AM   #13
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Do the rear, a big difference in reduced body roll. You'll be happy you did. It's almost x2 thickness than the stock one.
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      03-06-2013, 10:58 AM   #14
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Quote:
Originally Posted by MSport35TT View Post
Do the rear, a big difference in reduced body roll. You'll be happy you did. It's almost x2 thickness than the stock one.
Did you install your sway before or after or same time as coilovers?...coilovers alone might be enough to reduce most of that body roll.
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      03-06-2013, 11:23 AM   #15
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Quote:
Originally Posted by nitehawk View Post
Did you install your sway before or after or same time as coilovers?...coilovers alone might be enough to reduce most of that body roll.
I agree, for an E90 the coils should reduce the body roll and give your ride that sexy drop.
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      03-06-2013, 05:46 PM   #16
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Quote:
Originally Posted by nitehawk View Post
Did you install your sway before or after or same time as coilovers?...coilovers alone might be enough to reduce most of that body roll.
before... and with summer tires the car sticks!!! afterwards, the Coils when on I also did M3 rear end links and now the handling is MINT!!!


Deff do the rear sway!
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