[SSW]

I've got a 2008 335i E90 w/Sport Suspension, Koni FSDs and Michelin Pilot Super Sport tires on M193 rims (stock sizes) w/12 & 15mm spacers front and back. I'm also running w/a Cobb Stage 1+FMIC sport map tune w/a Mishimoto intercooler, which theoretically increases HP from 300 to 390, which is largely confirmed by my butt dyno.

When I run the car at speed into the turns, it tends to oversteer which may be in part due to the 12mm spacers that I'm running up front.

Was just told by a shop that the upper control arm (thrust) bushings on my E90 335i w/Sport Suspension are shot, so I've decided to replace the upper and lower control arms w/M3 parts. I'm also trying to decide whether to swap out the OEM E90 Sport Suspension (26.5-23mm) sway bar for either a M3 E90 (26.5mm) or M3 E93 (28.0-24.0mm) sway bar at the same time.

My understanding is that a stiffer front sway bar will increase understeer and, according to Turner Motosport, the M3 E90 and E93 sway bars are approximately 7% and 13% stiffer than the E90 OEM Sport Suspension sway bar, which should both help to compensate for the understeer that I am currently experiencing. See: E90 Front Sway Bar Upgrade Comparisons.

The question is which sway bar to go with. My guess is that the M3 E90 front sway bar will not change the handling of the car very much but that the M3 E93 front sway bar may over correct too much. No way of telling HOW MUCH unless I install and try both. My current thinking is to go w/the M3 90 sway bar and hope for a neutral effect rather than go w/the M3 E93 sway bar which may over correct.

Anyone have any experience w/the M3 E90 vs M3 E93 sway bars and their effects on handling on a basically stock E90?

Go with the M3 E93. It's definitely not "too stiff" for an otherwise mostly stock E90. I added one w/ just Bilstein B6s to complement my non-sport springs and the results were very refreshing. It only got better from there after adding M3 lowers and knocking out the alignment pin for more negative camber up front. Do all the above and you'll have a much more competent handling street car.

[SSW]

Originally Posted by FCobra94

Go with the M3 E93. It's definitely not "too stiff" for an otherwise mostly stock E90. I added one w/ just Bilstein B6s to complement my non-sport springs and the results were very refreshing. It only got better from there after adding M3 lowers and knocking out the alignment pin for more negative camber up front. Do all the above and you'll have a much more competent handling street car.

I admittedly don't know much about suspension. I've read talk about adding camber plates to increase the camber setting but never heard of taking out the alignment pin instead.

Just did a quick Google search on the topic and found an article which suggests a neg 1.4-1.6 camber setting and 0 toe in/out at the front. Posts in another article suggests similar settings for the front w/about neg 1.8-2 camber and 1/32-1/16 toe in at the rear.

Is this what you'd recommend?

See:

http://www.m3post.com/forums/showthread.php?t=521177
http://www.m3post.com/forums/showthread.php?t=367003

[SSW]

Originally Posted by SSW

Just did a quick Google search on the topic and found an article which suggests a neg 1.4-1.6 camber setting and 0 toe in/out at the front. Posts in another article suggests similar settings for the front w/about neg 1.8-2 camber and 1/32-1/16 toe in at the rear.

Is this what you'd recommend?

FWIW, Brandon at Precision Technic in Dublin (CA), where I plan to have the work done, also recommends the M3 E93 sway bar and thinks the above mentioned alignment specs would work well for street use. So, unless someone gives me a good reason to do otherwise, that's what I plan to do.

[Tom Droze]

Originally Posted by SSW

FWIW, Brandon at Precision Technic in Dublin, where I plan to have the work done, also recommends the M3 E93 sway bar and thinks the above specs would work well for street use. So, unless someone gives me a good reason to do otherwise, that's what I plan to do.

I went with the M3 e93 front sway bar along with the M3 front control arms, and with the exception of tires, they were the best handling mod I've done. There will be no understeer with the e93 FSB. I do recommend not changing the rear sway bar.

[cdgatti]

Originally Posted by Tom Droze

I went with the M3 e93 front sway bar along with the M3 front control arms, and with the exception of tires, they were the best handling mod I've done. There will be no understeer with the e93 FSB. I do recommend not changing the rear sway bar.

Tom - could you describe the handling improvements of the fsb separate from the control arms, or did you do them together?

[Tom Droze]

Originally Posted by cdgatti

Tom - could you describe the handling improvements of the fsb separate from the control arms, or did you do them together?

Unfortunately I did them both at the same time. However, the differnce in handling is quite remarkable. Understeer will be the last thing you will experience, as the car now feels like it wants to keep turning.

[cdgatti]

Originally Posted by Tom Droze

Unfortunately I did them both at the same time. However, the differnce in handling is quite remarkable. Understeer will be the last thing you will experience, as the car now feels like it wants to keep turning.

is it overly twitchy on the highway???

[Tom Droze]

Originally Posted by cdgatti

is it overly twitchy on the highway???

No, just more responsive to turning inputs but not overly twitchy.

Originally Posted by Tom Droze

I do recommend not changing the rear sway bar.

Have you tried a rear bar and then later removed it? I considered stepping up to an xi/e93 non-m rear bar if I were to ever drop the rear subframe. I'd imagine anything larger might give some undesired results without an LSD, etc.

[mojobmw_e90]

I have the same suspension mods as ssw other than my front spacers are 12mm and rear at 20mm.car handles very well. I have a ecs tuning front sway bar arriving today and will throw it on over the weekend. Should look into the ecs bar as its priced well for a 28mm bar

[Tom Droze]

Originally Posted by FCobra94

Have you tried a rear bar and then later removed it? I considered stepping up to an xi/e93 non-m rear bar if I were to ever drop the rear subframe. I'd imagine anything larger might give some undesired results without an LSD, etc.

I have not tried the rear sway bar. My recommendation is based on my HPDE instructor's feedback with regard to my car. After discussing the suspension changes I have made thus far (M3 front control arms, M3 front sway bar, eibach springs with Koni FSD shocks, rear subframe bushing inserts, MFactory LSD and differential bushings, Michelin PSS, and strut brace) and my desire to change the rear sway bar, he said my car feels "nicely neutral" and he wouldn't change a thing other than for me to keep logging more seat time.

The take away with regard to changing the rear sway bar is, for the vast majority of us, the juice just isn't worth the squeeze.

I have a video of my last HPDE where I keep reeling in a 135i in the corners who had a dyno verified 385 RWHP (at least 160 horsepower more than me). He would pull on me hard down the straights, as if I was out for a Sunday stroll, but I would catch him in the corners. Let me know if you want to see the video.

[SSW]

Originally Posted by Tom Droze

The take away with regard to changing the rear sway bar is, for the vast majority of us, the juice just isn't worth the squeeze.

That has been my assessment as well.

After changing to the M3 upper/lower control arms and M3 E93 front sway bar, I may change the rear subframe/diff bushings as you did but that would probably be it unless I want to take the next step by adding a Wavetrac LSD which can now be purchased around $1250 (about 50% less than not too long ago).

[cdgatti]

Originally Posted by Tom Droze

I have not tried the rear sway bar. My recommendation is based on my HPDE instructor's feedback with regard to my car. After discussing the suspension changes I have made thus far (M3 front control arms, M3 front sway bar, eibach springs with Koni FSD shocks, rear subframe bushing inserts, MFactory LSD and differential bushings, Michelin PSS, and strut brace) and my desire to change the rear sway bar, he said my car feels "nicely neutral" and he wouldn't change a thing other than for me to keep logging more seat time.

The take away with regard to changing the rear sway bar is, for the vast majority of us, the juice just isn't worth the squeeze.

I have a video of my last HPDE where I keep reeling in a 135i in the corners who had a dyno verified 385 RWHP (at least 160 horsepower more than me). He would pull on me hard down the straights, as if I was out for a Sunday stroll, but I would catch him in the corners. Let me know if you want to see the video.

Yea let's see it! Unless this is the one you posted previously?

[Tom Droze]

Originally Posted by cdgatti

Yea let's see it! Unless this is the one you posted previously?

It was previously posted.

[feuer]

Originally Posted by Tom Droze

I have a video of my last HPDE where I keep reeling in a 135i in the corners who had a dyno verified 385 RWHP (at least 160 horsepower more than me). He would pull on me hard down the straights, as if I was out for a Sunday stroll, but I would catch him in the corners. Let me know if you want to see the video.

HP is not the most relevant factor for fast track times, is not even in the top 3, but that is for a different thread.