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      05-10-2019, 08:49 AM   #1
Thunderguts
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Would I even want the 28 mm sway bar?

I'm planning the following suspension mods and I'm wondering if the 28mm front sway bar might actually downgrade handling.

My 128 already has the sport suspension with rear sway bar. I'm running a square setup with 225s on all corners. I'm planning to add BMW Performance springs (T1 all around) with Bilstein B8s and M3 control arms (definitely front, maybe rear). I'm hoping to get around 1.5° negative camber in the front and whatever I can get in the rear. I'm thinking the 28 mm Performance sway bar would reintroduce understeer, no?

Obviously the proper answer is to wait until I have the suspension set up, but sway bars are cheap and I could do it now while waiting to do the rest. I just don't want to bother if it's likely to make me understeer.

Would the increased negative camber in the front offset the larger sway bar and thus improve my overall grip while keeping the handling neutral?
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      05-10-2019, 11:31 AM   #2
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I also had Sport suspension and tried out the 29mm E93 M3 swaybar. I only got one track weekend down, and a bulk of it was wet and cold, but it seems to have made the front more willing to turn in and less likely to push through longer sweepers.

It's certainly possible it's a bit of placebo since this was the first weekend of the season for me, but it certainly didn't make things worse, if that's your concern.
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      05-10-2019, 12:30 PM   #3
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Good to know!
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      05-10-2019, 12:56 PM   #4
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Quote:
Originally Posted by Thunderguts View Post
I'm planning the following suspension mods and I'm wondering if the 28mm front sway bar might actually downgrade handling.

My 128 already has the sport suspension with rear sway bar. I'm running a square setup with 225s on all corners. I'm planning to add BMW Performance springs (T1 all around) with Bilstein B8s and M3 control arms (definitely front, maybe rear). I'm hoping to get around 1.5° negative camber in the front and whatever I can get in the rear. I'm thinking the 28 mm Performance sway bar would reintroduce understeer, no?

Obviously the proper answer is to wait until I have the suspension set up, but sway bars are cheap and I could do it now while waiting to do the rest. I just don't want to bother if it's likely to make me understeer.

Would the increased negative camber in the front offset the larger sway bar and thus improve my overall grip while keeping the handling neutral?
I would add Dinan camber plates up front, so that you can get at least 2° negative camber.

Larger sway bars up front can actually reduce understeer on cars with MacPherson struts up front. From this thread: https://www.1addicts.com/forums/showthread.php?t=677455

"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."
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      05-10-2019, 01:28 PM   #5
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Quote:
Originally Posted by duder13 View Post
I would add Dinan camber plates up front, so that you can get at least 2° negative camber.

Larger sway bars up front can actually reduce understeer on cars with MacPherson struts up front. From this thread: https://www.1addicts.com/forums/showthread.php?t=677455

"... 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.
This is why I went to the larger sway bar - I was looking at track photos and saw the outside wheel with clearly positive camber in several of the turns (I'm running M3 control arms and Dinan plates). I don't have the exact same angles for this event, but things look much better in this regard in the new set of photos.
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      05-10-2019, 02:16 PM   #6
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Quote:
Originally Posted by crowtrobot View Post
This is why I went to the larger sway bar - I was looking at track photos and saw the outside wheel with clearly positive camber in several of the turns (I'm running M3 control arms and Dinan plates). I don't have the exact same angles for this event, but things look much better in this regard in the new set of photos.
Yep, I'm also on M3 control arms, Dinan plates, and an M3 sway.
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      06-02-2019, 07:29 PM   #7
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Not seeing an increased understeer at all with an E93 M3 front bar, Square 225's, Bilstein B6's, Dinan camber plates, - 1.5 camber all around.
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      06-03-2019, 06:16 PM   #8
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I just put the E92 M3 sway bar on my 128i a few months ago. Really love the way the car handles now. Highly recommend this upgrade
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      06-03-2019, 06:43 PM   #9
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No. Sways fine tune the setup you get from geometry tires weight dampers, springs, driving style, etc.

In other words at the very least fix your camber setup, practice driving the car more, and change up your sways only when everything else is setup for badass performance. Otherwise you'll ruin the handling.

If you want to change the balance for more rotation and bite in the front adding negative camber in the front is the #1 mod to make that happen. The factory puts tons of negative camber in the rear and very little in the front stock so the car is more stable even without stability control.
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      06-04-2019, 03:57 AM   #10
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I found the front-end handling gains come from increased negative camber and a larger sway bar *together*. Do both mods, but not necessarily a large solid bar. Go for one of the BMW E92 or E93 M3 front bars if you can find one.

I'd say you need to change the rear subframe bushings before going any further with mods. Especially on cars that have done some mileage, the handling with stock subframe bushing is likely to get dangerous.
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      06-22-2019, 03:10 PM   #11
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I had a 28mm front bar, and then I deleted it. Much better...

That said, I have the spring rates and damping to support such a change. I'll have the static camber to support it eventually, but the car was performing artfully at Mid-Ohio two weeks ago without any more camber mods (Dinan plates and M3 control arms).

Now, when I was on my Koni's and Eibach springs, the 28mm sway bar helped a lot with the wallowing and softness of the car side-to-side. It made it much more stable at highway speeds, and fixed a lot of complaints I had about how the car felt.

Sway bars are merely tools for fine tuning. See how the car feels, and then add/remove bar rate to adjust as you see fit.
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      06-25-2019, 11:16 AM   #12
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OP, I had the same question, but my 128 doesn't have the sport package, so no rear bar. I have Koni's (pulled pins) and BMWP springs all around, and will have 245's square pretty soon. I'm trying to decide on a rear bar or a bigger front bar.

Edit: Sidenote, my car is used for daily driving and autocross. It will probably never see a track.

Last edited by skylarhagler; 06-25-2019 at 11:55 AM..
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      06-25-2019, 11:59 AM   #13
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Quote:
Originally Posted by skylarhagler View Post
OP, I had the same question, but my 128 doesn't have the sport package, so no rear bar. I have Koni's (pulled pins) and BMWP springs all around, and will have 245's square pretty soon. I'm trying to decide on a rear bar or a bigger front bar.

Edit: Sidenote, my car is used for daily driving and autocross. It will probably never see a track.
Somewhat the same situation re suspension. I have a 13mm rear ARB (stock is 12mm) waiting for me to get the motivation to install, but, I keep thinking about a thicker rear bar like an M3.
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      07-10-2019, 04:39 PM   #14
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Quote:
Originally Posted by skylarhagler View Post
OP, I had the same question, but my 128 doesn't have the sport package, so no rear bar. I have Koni's (pulled pins) and BMWP springs all around, and will have 245's square pretty soon. I'm trying to decide on a rear bar or a bigger front bar.

Edit: Sidenote, my car is used for daily driving and autocross. It will probably never see a track.
I'd stick with the stock bar up front (I removed mine when I went to much higher front spring rates). Now, as for the rear bar, I wouldn't recommend going thicker than 12-15mm without also getting an LSD. With the open diff and the eLSD's lackluster (but still remarkable) performance, you'll be roasting the inside coming out of corners, especially in a parking lot race
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      07-10-2019, 04:43 PM   #15
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I'd skip the bigger bar. Feels flatter but actually less mechanical grip and the car is slower through corners.

Stock is 26.5mm
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