Which sway bars for my setup...

zsapphire7 · 03-23-2009, 07:13 PM

So instead of blinding firing away at random set up sway bars, i decided to do some research first

. Id like to reduce body roll and eliminate understeer. I had a lot of trouble with understeer at the last autox event i was at. Im not sure what to do because i think on the track a little bit of understeer is fine while in autox the car just needs to be able to turn at slow speeds. It seems like sway bars can ruin all this very quickly if chosen poorly so im seeking advice. My current setup:

KW v2: 2012 springs in the rear
Staggered setup 19x8.5 front w/ 235/35/19 and 19x9.5 rear with 265/30/19.
Quaife LSD.

Everything else is stock. I believe most sway bars have been designed with an open differntial in mind and want to reduce inside wheel slip. Im more interested in making the handling at the limits predictable. ATBs can transfer 80/20 instantly when the inside wheel begins to slip. If this happens too suddenly, id imagine a snap oversteer situation would occur since the sudden 50/50 is distrupted. Idealy i would like the inside wheel to slowly lose grip forcing the LSD to slowly transfer power to the outside, 60/40, then 70/30, and so on to the max.

I read up on Mr 5's F/R biasing when selecting sways but am not sure if i understand everything properly. Should I go with Hotchkis for a near 92.2/7.8 split... or Hotchkis front and M3 rear sway for a 85.5/14.5 split? What is the M3 stock bias? I'm just wondering if i should aim for a stiffer rear setup or try to stay closer to the stock bias. Would a stiffer or softer rear make the tq transfer from the LSD be more linear/even at the limit in a turn?

My knowledge of suspension tuning and improvement is pretty elementary so please be patient with me

. Im open to all sorts of advice and am just looking to learn more and also trying to get my car into tip top shape!

Mr. 5 · 03-23-2009, 08:27 PM

I actually eliminated the sway bar discussion from the sticky since it started to get really confusing and I have recently learned that it does not only have to do with front and rear biasing.
Increasing the rear bar diameter will definitely balance the car out and create less understeer.

mike-y · 03-24-2009, 11:05 AM

more rear bar or more rear spring will reduce understeer. Or you can try running the same size tires up front as you do in the rear (or vice versa) when you auto-x. Though there can be issues with running a rear bar that is too large/stiff for your spring rate, so you don't always want to get the largest bars you can get your hands on.

zsapphire7 · 03-24-2009, 11:33 AM

im wondering what combination to go with tho. Obviously i want a stiffer rear but if i change out the front to be stiffer too, it means the rear has to be stiffer porportionally.

Options options... Should i get stiffer rear springs +~10% (2012 to 2017?)

does anyone know more information about the front oem m3 sway? I wonder how much stiffer than stock it is..

tapengl · 03-24-2009, 08:18 PM

Quote:

Originally Posted by zsapphire7

im wondering what combination to go with tho. Obviously i want a stiffer rear but if i change out the front to be stiffer too, it means the rear has to be stiffer porportionally.

Options options... Should i get stiffer rear springs +~10% (2012 to 2017?)

does anyone know more information about the front oem m3 sway? I wonder how much stiffer than stock it is..

I had same thought as you so I choose Hotchiks.
According to their website, front is 95% stiffer than stock and 105% on the rear. I do feel the flat turn is very well balanced.

dvpouldar26 · 03-24-2009, 08:32 PM

I think that a little bit of understeer at the track is a good thing to let you know where your cars limits are. It lets you know when you are puching your car too hard. As for the autocrossing, i would try a square wheel and tire setup, see how much understeer there is from there, and make the changes accordingly. If there still is understeer in the rear, i would get a sway bar in the rear such as the UUC, H&R, Hotchkis, or m3 sway bars.

TSM330i · 03-24-2009, 10:26 PM

I'd try adjusting your shocks first to help the understeer. Stiffen up the rears and soften the fronts. This will allow you to bite in the front better while the rear should be able to slide around and put your LSD to use.
If that doesn't work, I highly recomment UUC Swaybars. If you're going to get swaybars, why wouldn't you get ones that are adjustable? While you're changing the rear bar, maybe get the stiffer sub-frame mounts while you're at it.

HP Autosport · 04-01-2009, 01:31 AM

Quote:

Originally Posted by zsapphire7

So instead of blinding firing away at random set up sway bars, i decided to do some research first

. Id like to reduce body roll and eliminate understeer. I had a lot of trouble with understeer at the last autox event i was at. Im not sure what to do because i think on the track a little bit of understeer is fine while in autox the car just needs to be able to turn at slow speeds. It seems like sway bars can ruin all this very quickly if chosen poorly so im seeking advice. My current setup:

KW v2: 2012 springs in the rear
Staggered setup 19x8.5 front w/ 235/35/19 and 19x9.5 rear with 265/30/19.
Quaife LSD.

Everything else is stock. I believe most sway bars have been designed with an open differntial in mind and want to reduce inside wheel slip. Im more interested in making the handling at the limits predictable. ATBs can transfer 80/20 instantly when the inside wheel begins to slip. If this happens too suddenly, id imagine a snap oversteer situation would occur since the sudden 50/50 is distrupted. Idealy i would like the inside wheel to slowly lose grip forcing the LSD to slowly transfer power to the outside, 60/40, then 70/30, and so on to the max.

I read up on Mr 5's F/R biasing when selecting sways but am not sure if i understand everything properly. Should I go with Hotchkis for a near 92.2/7.8 split... or Hotchkis front and M3 rear sway for a 85.5/14.5 split? What is the M3 stock bias? I'm just wondering if i should aim for a stiffer rear setup or try to stay closer to the stock bias. Would a stiffer or softer rear make the tq transfer from the LSD be more linear/even at the limit in a turn?

My knowledge of suspension tuning and improvement is pretty elementary so please be patient with me

. Im open to all sorts of advice and am just looking to learn more and also trying to get my car into tip top shape!

How about just add the M3 front and rear anti roll bars for a balanced handling. I think you may find the aftermarket ARB's a little bit on the stiff side.

zsapphire7 · 04-01-2009, 05:54 PM

Actually i have thought about the M3 rear and front sway bars. I think this a pretty likely path for me to go. I only wonder about putting in the rear subframe mounts as well. Do the rear subframe mounts help that much or make that much a noticeable difference?

Also does anyone have information on the front M3 sway bar as to how much more stiff it is compared to ZSP oem 335i front ones? It seems as tho the rear M3 sway bar is significantly more stiff than any other aftermarket rollbar except the H&R. (from Orb's stiffness sheet.)

03-23-2009, 07:13 PM	#1
zsapphire7 Colonel 104 Rep 2,368 Posts Drives: 08 e92 M3 Join Date: Oct 2007 Location: SF Bay Area iTrader: (21)	Which sway bars for my setup... So instead of blinding firing away at random set up sway bars, i decided to do some research first . Id like to reduce body roll and eliminate understeer. I had a lot of trouble with understeer at the last autox event i was at. Im not sure what to do because i think on the track a little bit of understeer is fine while in autox the car just needs to be able to turn at slow speeds. It seems like sway bars can ruin all this very quickly if chosen poorly so im seeking advice. My current setup: KW v2: 2012 springs in the rear Staggered setup 19x8.5 front w/ 235/35/19 and 19x9.5 rear with 265/30/19. Quaife LSD. Everything else is stock. I believe most sway bars have been designed with an open differntial in mind and want to reduce inside wheel slip. Im more interested in making the handling at the limits predictable. ATBs can transfer 80/20 instantly when the inside wheel begins to slip. If this happens too suddenly, id imagine a snap oversteer situation would occur since the sudden 50/50 is distrupted. Idealy i would like the inside wheel to slowly lose grip forcing the LSD to slowly transfer power to the outside, 60/40, then 70/30, and so on to the max. I read up on Mr 5's F/R biasing when selecting sways but am not sure if i understand everything properly. Should I go with Hotchkis for a near 92.2/7.8 split... or Hotchkis front and M3 rear sway for a 85.5/14.5 split? What is the M3 stock bias? I'm just wondering if i should aim for a stiffer rear setup or try to stay closer to the stock bias. Would a stiffer or softer rear make the tq transfer from the LSD be more linear/even at the limit in a turn? My knowledge of suspension tuning and improvement is pretty elementary so please be patient with me . Im open to all sorts of advice and am just looking to learn more and also trying to get my car into tip top shape!
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03-23-2009, 08:27 PM	#2
Mr. 5 Modder Raider 753 Rep 8,633 Posts Drives: M3 Join Date: Apr 2007 Location: Surf City, HB iTrader: (31) Garage List 2007 e90 335i [8.00]	I actually eliminated the sway bar discussion from the sticky since it started to get really confusing and I have recently learned that it does not only have to do with front and rear biasing. Increasing the rear bar diameter will definitely balance the car out and create less understeer. __________________ e36 M3 Coupe, e36 325i Sedan e90 335i--SOLD Best 60-130-------------9.15 Seconds------------------WWW.MR5RACING.COM
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03-24-2009, 11:05 AM	#3
mike-y just another bmw douche bag 195 Rep 3,640 Posts Drives: 1.9L of fury Join Date: Nov 2008 Location: Los Angeles, CA iTrader: (4)	more rear bar or more rear spring will reduce understeer. Or you can try running the same size tires up front as you do in the rear (or vice versa) when you auto-x. Though there can be issues with running a rear bar that is too large/stiff for your spring rate, so you don't always want to get the largest bars you can get your hands on.
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03-24-2009, 11:33 AM	#4
zsapphire7 Colonel 104 Rep 2,368 Posts Drives: 08 e92 M3 Join Date: Oct 2007 Location: SF Bay Area iTrader: (21)	im wondering what combination to go with tho. Obviously i want a stiffer rear but if i change out the front to be stiffer too, it means the rear has to be stiffer porportionally. Options options... Should i get stiffer rear springs +~10% (2012 to 2017?) does anyone know more information about the front oem m3 sway? I wonder how much stiffer than stock it is..
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03-24-2009, 08:32 PM	#6
dvpouldar26 Major 64 Rep 1,498 Posts Drives: 2008 e92 328i, Porsche 987.1 Join Date: May 2008 Location: Beverly Hills, CA iTrader: (4)	I think that a little bit of understeer at the track is a good thing to let you know where your cars limits are. It lets you know when you are puching your car too hard. As for the autocrossing, i would try a square wheel and tire setup, see how much understeer there is from there, and make the changes accordingly. If there still is understeer in the rear, i would get a sway bar in the rear such as the UUC, H&R, Hotchkis, or m3 sway bars.
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03-24-2009, 10:26 PM	#7
TSM330i 2006 330i, TSM, Black, manual, sport 878 Rep 3,699 Posts Drives: '17 C2, GTI, Z4 3.0si Racecar Join Date: Nov 2005 Location: Chester Springs, PA iTrader: (2)	I'd try adjusting your shocks first to help the understeer. Stiffen up the rears and soften the fronts. This will allow you to bite in the front better while the rear should be able to slide around and put your LSD to use. If that doesn't work, I highly recomment UUC Swaybars. If you're going to get swaybars, why wouldn't you get ones that are adjustable? While you're changing the rear bar, maybe get the stiffer sub-frame mounts while you're at it. __________________ 2017 Porsche C2 - manual of course 2015 GTI S 2008 BMW Z4 3.0si Coupe - because racecar
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04-01-2009, 05:54 PM	#9
zsapphire7 Colonel 104 Rep 2,368 Posts Drives: 08 e92 M3 Join Date: Oct 2007 Location: SF Bay Area iTrader: (21)	Actually i have thought about the M3 rear and front sway bars. I think this a pretty likely path for me to go. I only wonder about putting in the rear subframe mounts as well. Do the rear subframe mounts help that much or make that much a noticeable difference? Also does anyone have information on the front M3 sway bar as to how much more stiff it is compared to ZSP oem 335i front ones? It seems as tho the rear M3 sway bar is significantly more stiff than any other aftermarket rollbar except the H&R. (from Orb's stiffness sheet.)
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