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Suspension & Braking Forum by BimmerWorld
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Old 09-09-2008, 07:01 PM   #1
ari00
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High speed braking stability question...

Hi all, I appreciate any time taken to help me out...

I've got an '04 330ci with a bunch of suspension mods. Only reason I will list them is to explain my dilema.

-Bilstein PSS9 coilovers set to 2 (second stiffest setting) and 4 new springs sent under warranty last year.

-Powerflex front and rear CABs, M3 OEM inner upper and lower trailing arm bushings

-Turner adjustable rear camber arms

-Turner sways set to the stiffest settings front and rear

Also, Stoptech front and rear rotors, Axxis Ultimate pads, and stainless brake lines

When I brake at higher speeds, my car tends to sway to either side...just doesn't feel as "solid" as it ised to under braking. I have not yet replaced my steering coupler (I have almost 112k miles on my car). Wheels are 19", but the same size I've run for the last 5 years. I just can't place my finger on what the issue could be.

The car is pretty much set up to be stiff, and the only thing I can think of is my coilover springs are set at maximum height (although they have settled so much that the tire is flush with the wheelwell. They are, however, Bilstein coilover springs, and I think they should keep the car more stable should this be the culprit. This is the only thing I can think of, but the shocks and struts are set pretty stiff so I thought this would compensate for the lack of spring compression.

Sorry for the long post, but just wanted to cover all the mods and explain my spring height to see if any suspension experts might have some feedback.

Thanks again for any help!
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Old 09-09-2008, 07:13 PM   #2
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What's are your alignment settings at and when were they last done?

Off the top of my head, I'd say bump up the rear toe settings a bit. If it's been a while since you had an alignment, the thing to look for would be some camber loss on the RR wheel. That one tends to slip a bit under load.
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Old 09-09-2008, 07:19 PM   #3
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John...Thank you VERY much for a reply.

I have to get back to work, but I will have an alignment done soon. It's been about a year since I had one, and obviously I've played with my car's height. Not even sure if this would be an issue, but I'll check rear camber and rear toe as well. Much appreciated!
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Old 09-09-2008, 08:34 PM   #4
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The stiffest settings are not always the best when dealing with wiggle under high speed braking. You said you had the springs replaced before... were they replaced with the same spring rates? changing springs rates dramatically affects cars rotation and stability under braking. Mess around with your alignment. Most likely it is out of wack since you did mess with the height of your car. If its tracked often, im sure you've ran over berms which does cause alignment to shift from time to time. If all is figured out and the car still wiggles, then you might want to look into a rear GT wing for stability into sweeper like turns as well as a front splitter for equal down force front and rear.

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Old 09-09-2008, 10:12 PM   #5
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[QUOTE=VelocityMotoring;8508101]The stiffest settings are not always the best when dealing with wiggle under high speed braking. You said you had the springs replaced before... were they replaced with the same spring rates? changing springs rates dramatically affects cars rotation and stability under braking. Mess around with your alignment. Most likely it is out of wack since you did mess with the height of your car. If its tracked often, im sure you've ran over berms which does cause alignment to shift from time to time. If all is figured out and the car still wiggles, then you might want to look into a rear GT wing for stability into sweeper like turns as well as a front splitter for equal down force front and rear.


Charles, I thank you as well for your prompt reply. I thought (most likely incorrectly) that the stiffer the setting on shocks and struts, assuming a smooth flat surface of course, the better the control of the vehicle. The springs were replaced under Bilstein's warranty (with a slight charge incurred) because I felt they settled too much in a short amount of time. I fully understand all springs settle over time, but these are beyond what I feel is reasonable. I have the same issue with the new ones as well. I've had at least 8 cars with all sorts of aftermarket springs in the past, and they've never settled this much or this quickly before. But I digress.

I'll definitely get an alignment soon, and I do have splitters in front (at least the CF splitters provided with my CSL front bumper. As far as a rear GT wing, while I understand it's benefits at high speeds, This is something my car has recently developed and would like to pinpoint what the problem is rather than go to such extremes. I do appreciate the suggestion though.

I only wish there were some springs available with a higher spring rate that would work in conjunction with the PSS coilover shocks and struts. I could then soften the settings and not worry about the slammed look.
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Old 09-09-2008, 10:13 PM   #6
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Check those OE trailing arm bushings when you do the alignment too.
Mine are currently shot, and the back end has become twitchy over any surface imperfections. It increases with speed, and on the brakes it seems to twitch a little more. But I also have about 200lbs of sh1t in my trunk so my weight distribution is better than the average sedan.
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Old 09-09-2008, 10:26 PM   #7
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Check those OE trailing arm bushings when you do the alignment too.
Mine are currently shot, and the back end has become twitchy over any surface imperfections. It increases with speed, and on the brakes it seems to twitch a little more. But I also have about 200lbs of sh1t in my trunk so my weight distribution is better than the average sedan.
Good thought but I believe he mentioned having PowerFlex bushings in there already. Probably not the cuplrit.
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Old 09-09-2008, 10:31 PM   #8
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I only wish there were some springs available with a higher spring rate that would work in conjunction with the PSS coilover shocks and struts. I could then soften the settings and not worry about the slammed look.
This is one of the key reasons I decided against going with a PSS setup - no spring choices. Of course, I paid a tidy sum for my flexibility....
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Old 09-09-2008, 10:35 PM   #9
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Good thought but I believe he mentioned having PowerFlex bushings in there already. Probably not the cuplrit.
Thanks...Yeah, I did Powerflex trailing arm bushings as well as inner upper and lower OEM M3 control arm bushings. I always mix up trailing and cab's but I've replaced all those. Also did tie rods and sway bar endlinks as well as my entire list above. My car was all over the place when switching lanes before I did the bushings and control arms. Even though I went with the HD control arms and ball joints, I'll have to check the ball joints soon JUST to be on the safe side...

Thanks again for all your suggestions guys. It's my 3rd E46 covering over 275k miles between the 3 of them, so I'm usually pretty good about pinpointing issues (especially with all of our members' help over the years!). It's just frustrating. I'll do the alignment and play around with the rear parameters a bit for starters. I seriously hope it's not my ball joints already...hasn't even been a year and went with the HD ones too.
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Old 09-09-2008, 10:38 PM   #10
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This is one of the key reasons I decided against going with a PSS setup - no spring choices. Of course, I paid a tidy sum for my flexibility....
If you don't mind me asking, what setup did you go with? I figure, since it's been 5 years, maybe I can convince my GF that it's a worthwhile investment to swap out suspensions (soon to be fiance guys...I'm not THAT whipped).
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Old 09-09-2008, 10:49 PM   #11
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If you don't mind me asking, what setup did you go with? I figure, since it's been 5 years, maybe I can convince my GF that it's a worthwhile investment to swap out suspensions (soon to be fiance guys...I'm not THAT whipped).
I just installed a set of AST 4100 coilovers from Vorshlag a little over 2 weeks ago. I'm running 500f/550r linear rate springs, still playing with rebound settings a bit. Vorshlag stocks a wide range of spring rates but I don't think I'll need to change from what I've got. My main goal was to add enough spring rate to compensate for the mass of the twin screw supercharger and restore the car's balance. Mission accomplished. So far I've been very impressed with this setup which I've got paired with H&R sways.
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Old 09-09-2008, 11:30 PM   #12
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I just installed a set of AST 4100 coilovers from Vorshlag a little over 2 weeks ago. I'm running 500f/550r linear rate springs, still playing with rebound settings a bit. Vorshlag stocks a wide range of spring rates but I don't think I'll need to change from what I've got. My main goal was to add enough spring rate to compensate for the mass of the twin screw supercharger and restore the car's balance. Mission accomplished. So far I've been very impressed with this setup which I've got paired with H&R sways.
I'll have to check them out. I've looked at their website and spoke to them about a possible LS1 swap in the future (sorry to bring up a sore topic...that's all I'll say until I ACTUALLY do it...IF I ever do!). I have yet to actually look at their suspension offerings. I'm sure the setup is not cheap, but I do understand they offer lots of great tested products.
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Old 09-10-2008, 08:14 AM   #13
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I'll have to check them out. I've looked at their website and spoke to them about a possible LS1 swap in the future (sorry to bring up a sore topic...that's all I'll say until I ACTUALLY do it...IF I ever do!). I have yet to actually look at their suspension offerings. I'm sure the setup is not cheap, but I do understand they offer lots of great tested products.
There aren't a lot of reviews of the AST products for the e46 platform, although there are a few on m3forum. The most useful information can be found over at bimmerforums as they are pretty heavily discussed by the e36 owners over there in the track forum. Once I've had them a little longer I plan to post a more complete review here.
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Old 09-10-2008, 09:50 AM   #14
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I have almost the same setup except I have PSSs which are set to the highest level. I run 17" or 18" wheels. I believe the PSSs are equivalent to 6 setting on a PSS9. I also have the UUC Wilwood BBK and I have no issues with uneven braking.

What condition are your tires in? Did you check the pressure? I can always tell when a tire is low when I brake.
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Old 09-13-2008, 10:30 AM   #15
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I have almost the same setup except I have PSSs which are set to the highest level. I run 17" or 18" wheels. I believe the PSSs are equivalent to 6 setting on a PSS9. I also have the UUC Wilwood BBK and I have no issues with uneven braking.

What condition are your tires in? Did you check the pressure? I can always tell when a tire is low when I brake.
The tire pressure and tread are both perfect, as I check them often. What I did find was my driver's side tie rod was bent from a pothole I hit a few months back. My rim has been straightened, and I will install the new tie rod this coming week.

While I realize this can play a role in stability and braking, I hope this eliminates that wobbly feeling during the high speed braking. Can't seem to remember if I had this symptom before I hit the pothole.

Thanks again to all who have pitched in...much appreciated!

Ari
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Old 09-13-2008, 11:08 AM   #16
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I'm sure a bent tie rod will cause some high speed instability.
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Old 09-13-2008, 08:46 PM   #17
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Quote:
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I only wish there were some springs available with a higher spring rate that would work in conjunction with the PSS coilover shocks and struts. I could then soften the settings and not worry about the slammed look.

I have PSS9's and I switched out my front springs when I put TCK camber plates in. I went with 400# springs because they were the closest to the Bilstein springs, but you could get stiffer springs...

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Old 09-16-2008, 07:27 PM   #18
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im sorta felling like my brakes lack high speed bite and that probably from my sucky akebono's, as the others have said the stiffest setting isnt always good, over the weekend i put my KW V2's on almost full soft in the front, and WWWWWWWWWOOOOOOOOOOOOWWWWWWWWWWWWW, what a difference, its sooo smooth, i was going 125 on the freeway and it was sooooooooooo smooth, and check this out, my steering wheel would slightly shake above 65-80 but now its pretty much gone afte i put it on the soft setting, i still have not gotten an allignment btw.
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Old 09-21-2008, 10:56 PM   #19
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I have PSS9's and I switched out my front springs when I put TCK camber plates in. I went with 400# springs because they were the closest to the Bilstein springs, but you could get stiffer springs...


Whoa...I had no idea you could swap out springs on a PSS9 kit. May I ask which springs you went with specifically, and also if you know what other springs I could swap? I feel like such a noob, but thanks in advance!
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Old 09-28-2008, 10:20 PM   #20
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I just wanted to update you guys who responded regarding this thread. I ended up replacing my steering coupler, and boy, WHAT A DIFFERENCE. You may not notice it under typical driving, but when braking into a turn or even hitting large puddles on the highway, the car now stays where you put it. BIG difference. I've got over 112k miles and my original coupler showed no signs of wear but the new one sure did make a world of difference, as well as braking in the rain. No more pulling one way or the other at highway speeds.
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