Suspension help. Rear end shimmy still.

Optigrab

Corporal
Sep 19, 2018
133
Thank you for that information regarding the suspension, very good read. I have a question. So if one changes the stock Non-M suspension. They should no longer use stock alignment specs? I ask as I have done a few things to the suspension and keep burning through rear tires. I have Eibach Springs, Bilstein shocks, Front M3 arms, aftermarket rear camber arms and Toe arms ( a friend gave them to me) and Rear Subframe Inserts. I recently noticed the Rear toe arms I had were crap and had a bunch of play( but this was one of the best upgrades to the suspension to me as in stability wise). So i ordered Some Meagan arms as they have good reviews and not much complaint about noise like with some of the higher end Toe arms. But now i wonder if maybe I just have to use different alignment specs?
Gotcha... @Silver_Sur4r_N54 was looking for alignment specs because he said he kept wearing out rear tires.

@Silver_Sur4r_N54 is it street driving that is wearing out the rear tires? How is the wear... across the whole tread or on the inside? Premature wear can mainly be a culprit of too much toe scrubbing the tire tread.

If you were to measure the rear toe change under bump with no load on the suspension (i've done this) you will get zero toe change. When you accelerate, the wheel will be pushed toward the front of the car and as the suspension squats (bump), there will now be a toe change, IE toe in. Assuming your car is stable under acceleration, what I suspect is happening is there is too much toe in as you accelerate. To solve this you would want to start with less "static" toe in on your alignment. This will result in less toe in under acceleration reducing tire wear. You will have to play around with this or maybe someone over at 1addicts, like @Optigrab suggested, has done it which will save you some time figuring it out.

Unfortunately I won't have a conclusion soon as I have another project getting in the way (grrr...). However I am looking to figure this out ASAP for developing e90 track suspensions. Hopefully in the coming weeks.
Some info here

https://www.n54tech.com/forums/showthread.php?t=30461
 

[email protected]

Corporal
Platinum Vendor
Jun 4, 2018
136
This is why I'm studying the rear suspension in detail. There just seems to be some not so accurate info out there. For example... Someone in that thread says the following which is not true: "Under braking for example the wheels will tend to toe out beyond zero"

I'll repost this from earlier, which is BMW documentation. Y axis is bump/rebound. So 1 is when the suspension compresses (bump), 2 is ride height, and 3 is when the suspension droops (rebound). The X axis is toe where towards the right (4) is toe in, IE positive toe. When braking the front compresses and the rear droops. So if you look at the green line (braking) you will see when the suspension droops (section 3) the rear toes IN. This is good as it creates stability.

bump curves.JPG


There is some other info in that thread about tire wear that I disagree with but its a moot point for this thread discussion.
 

Bnks334

Sergeant
Dec 1, 2016
269
New York
This is why I'm studying the rear suspension in detail. There just seems to be some not so accurate info out there. For example... Someone in that thread says the following which is not true: "Under braking for example the wheels will tend to toe out beyond zero"

I'll repost this from earlier, which is BMW documentation. Y axis is bump/rebound. So 1 is when the suspension compresses (bump), 2 is ride height, and 3 is when the suspension droops (rebound). The X axis is toe where towards the right (4) is toe in, IE positive toe. When braking the front compresses and the rear droops. So if you look at the green line (braking) you will see when the suspension droops (section 3) the rear toes IN. This is good as it creates stability.

View attachment 17835

There is some other info in that thread about tire wear that I disagree with but its a moot point for this thread discussion.
Is this a chart for the front or rear axel? Pretty sure this is from the "E90 suspension" BMW academy doc?
 

Optigrab

Corporal
Sep 19, 2018
133
This is why I'm studying the rear suspension in detail. There just seems to be some not so accurate info out there. For example... Someone in that thread says the following which is not true: "Under braking for example the wheels will tend to toe out beyond zero"

I'll repost this from earlier, which is BMW documentation. Y axis is bump/rebound. So 1 is when the suspension compresses (bump), 2 is ride height, and 3 is when the suspension droops (rebound). The X axis is toe where towards the right (4) is toe in, IE positive toe. When braking the front compresses and the rear droops. So if you look at the green line (braking) you will see when the suspension droops (section 3) the rear toes IN. This is good as it creates stability.

View attachment 17835

There is some other info in that thread about tire wear that I disagree with but its a moot point for this thread discussion.
It would not surprise me if some of the people with issues had bent or damaged suspension components
either way the more info the better. Not sure if any of the time attack cars have posted their alignment info....
it would be interesting to see. Good luck!
 

Rob09msport

Captain
Oct 28, 2017
1,151
Monroe CT
Did you mean to post different links as they are both the same? I saw this a long time ago and what fe1rx did was awesome. His study was the difference in the structural differences between the M3 arm and the non m arm. He didn't discuss geometry at all really. I will admit I did skim it and could have missed a post where he did discuss geometry.
Yes I had 2 links don't know how I did that I'll fix when I get home im driving encase geico asks lol
 

Asbjorn

Sergeant
Mar 10, 2018
284
Europe, based in China
You are welcome! I love suspension stuff. Anyone feel free to ask me anything suspension related!

Cheers,
Barry
Really enjoy reading about your findings. I am all bearings up front now, and had no idea I was changing toe behavior away from the intended design.

I would really love your inputs on how to adjust camber in this thread. At this point I am trying to figure out what the right direction is. Ie if I need less tire pressure or less camber to get towards a more even contact patch on track. Some of my track buddies run much more camber than me.
 
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Reactions: Silver_Sur4r_N54
Jan 5, 2018
34
South Jersey
Gotcha... @Silver_Sur4r_N54 was looking for alignment specs because he said he kept wearing out rear tires.

@Silver_Sur4r_N54 is it street driving that is wearing out the rear tires? How is the wear... across the whole tread or on the inside? Premature wear can mainly be a culprit of too much toe scrubbing the tire tread.

If you were to measure the rear toe change under bump with no load on the suspension (i've done this) you will get zero toe change. When you accelerate, the wheel will be pushed toward the front of the car and as the suspension squats (bump), there will now be a toe change, IE toe in. Assuming your car is stable under acceleration, what I suspect is happening is there is too much toe in as you accelerate. To solve this you would want to start with less "static" toe in on your alignment. This will result in less toe in under acceleration reducing tire wear. You will have to play around with this or maybe someone over at 1addicts, like @Optigrab suggested, has done it which will save you some time figuring it out.

Unfortunately I won't have a conclusion soon as I have another project getting in the way (grrr...). However I am looking to figure this out ASAP for developing e90 track suspensions. Hopefully in the coming weeks.
apologies for not replying sooner but... I am wearing tires on the inside edge... I do not track with this car. It is all street driving... Spirited of course, a lot of hard launches and quick acceleration. But I believe you are right about the changes in Toe. When I had a e38 7 series that was lowered I would had the same problem with rear tires but replacing most of the rear suspension bushings helped tremendously. Thought possibly could be the same with the e92. But i think the Toe changes added with more power is just causing me to run the tires down faster.
 

E90TommyB

Lurker
Apr 9, 2018
15
Indiana
Im currently having the same issues and can not figure it out. The rear end wanders under power but is fine when I'm just cruising. I've been battling this issue for a while now and have done just about everything and am still having this issue. So far i've done m3 rear control arms, God Speed toe arms, solid subframe and diff bushings, upgraded sway bar in the front and rear. I have upgraded lower control arm bushings and upgraded rear trailing arm bushings to that i have yet to install. I've had the car re-aligned 4 times and no matter how we set the alignment the rear end still wanders. I have firestone fire hawk indy 500 tires o the car that have roughly 2k miles on them so i don't think the tires are the issue but ill swap some different tires on the rule that out. Other than that i'll install the rear lower control arm bushings and rear trailing arm bushings and go from there. Hopefully it solves my issues but any help is appreciated.
 

Torgus

Captain
Nov 6, 2016
1,033
Boston
Im currently having the same issues and can not figure it out. The rear end wanders under power but is fine when I'm just cruising. I've been battling this issue for a while now and have done just about everything and am still having this issue. So far i've done m3 rear control arms, God Speed toe arms, solid subframe and diff bushings, upgraded sway bar in the front and rear. I have upgraded lower control arm bushings and upgraded rear trailing arm bushings to that i have yet to install. I've had the car re-aligned 4 times and no matter how we set the alignment the rear end still wanders. I have firestone fire hawk indy 500 tires o the car that have roughly 2k miles on them so i don't think the tires are the issue but ill swap some different tires on the rule that out. Other than that i'll install the rear lower control arm bushings and rear trailing arm bushings and go from there. Hopefully it solves my issues but any help is appreciated.
Did you code out your E diff already?

I can't imagine the tires will make a large change.
 

E90TommyB

Lurker
Apr 9, 2018
15
Indiana
Shock spring setup?
The previous owner of my car had eBay coilovers on the car when i bought it that are similar to BC coilovers. I checked the rear shocks and they're not shot so i figured they weren't the problem. You think it could be the coilovers?
 
Last edited:

derekgates

Specialist
Feb 23, 2018
95
NW FL
What did you end up using to code that out? I still need to do that after installing the mechanical lsd
http://www.onelapx1.com/blog/how-to-make-your-bmw-actually-fun

Electronic nannies are a veritable alphabet soup of joy-sucking, fun-killing, brake-destroying awfulness. DSC, DTC, HBA, EVB, HPS, and Maximum Brake Support are all BMW acronyms that stand for the same thing - SLOW. Each and every one of these electronic safety devices are designed for the average consumer; not your hardcore automotive enthusiast. It is surprising to me that information on how to disable these "features" is not more widely available.

While the race to integrate technology into cars has cost us some raw dynamic pleasure, one benefit is that almost everything in a modern car is programmable - if you know how to do it. In the BMW world, we call it "coding." Coding is essentially the act of using BMW diagnostic software to access computer "modules" that control various parts of your car. This software allows you to read out the various options available and change them to suit your preferences. Generally there are two types of options for each coding parameter: "aktiv" or "nicht_aktiv," and level based entries where you will choose "levels" such as "wert_01," "wert_02," etc. Coding can be confusing to set up, but a little perseverance can go a long way towards customizing your car. Luckily for us, all of these electronic nannies can be found and modified in your DSC (dynamic stability control) module. The name of this module varies depending on what car you have, but as an xDrive N55 car these nannies were located in the DSC_84.C04 file of my XDSC module. Explaining how to set up your computer for coding is beyond the scope of this blog, but I will provide which options you need to disable, and what the proper setting is.
I hope it will be useful to have the description of these nannies consolidated in one place. This information is scattered all over the internet; I would have appreciated having it in one place when I was doing my own research. Each of these nannies are present on N52, N54 and N55 vehicles, including the 128i, 135i, 238i, 335i, 535i, and X1. The following chart is organized with the name of the electronic nanny followed by the acronym it is listed as in BMW's DSC module files.
Please note - if the option in your DSC module appears different (for example, it you have various "werts" as an option instead of "nicht_aktiv" or "aktiv"), you can examine the hex data in the entry to see what the various "wert" levels are. For example, the N54 335i electronic differential setting is not a simple on/off setting, but the hex data for "wert_01" is equivalent to "nicht_aktiv." You can refer to this thread for more info: http://www.e90post.com/forums/showthread.php?t=944126


The Definitive Guide to BMW's Joy-Killing Nannies

Engine Power Reduction to Prevent Brake Disc Overheating (FLR)

N55 X1 Parameter: e84_FLR
N54 335i xDrive Parameter: FLR_C0F
This is the worst of them all. Modern BMWs will actively cut the throttle in the middle of your track day if it has reason to believe that your brake pads are overheating. Normally, this wouldn't be such a bad thing - nobody wants to crash into ARMCO going 140mph. The problem is, your BMW doesn't actually have temperature sensors anywhere in the braking system. The computer relies on a "calculated" brake disc temperature based on several inputs including ground speed, brake pedal application force, and the frequency with which the electronic differential applies "torque-vectoring" braking. Your BMW has no way to know that you installed a Stoptech Big Brake Kit with Castrol SRF fluid and Performance Friction PFC01 pads. It just assumes you are running the stock system and cuts your throttle based on values that would overheat the OEM brake pads. Unacceptable to say the least, and occasionally dangerous. It was not a good experience braking from 145mph down to 45mph with a GT3 three feet off my rear bumper, only to have zero power coming out of the turn. This could very plausibly cause an accident on track.

To disable, set to "nicht_aktiv."

Brake Fading Compensation (HPS)
N55 X1 Parameter: e84_HPS
N54 335i xDrive Parameter: HPS
It is insane that a "performance" car has this feature. Brake fade compensation "calculates" the temperature of your fluid in a similar manner to the above "Engine Power Reduction to Prevent Brake Disc Overheating" parameter does. The higher the calculated temperature of your brake fluid (remember, there is no real sensor), the more hydraulic assist will be added to your brake pedal. In theory, this masks brake fade on the street. On the track, it makes a consistent brake pedal literally impossible. If you are tracking the car, you should have upgraded pads and fluid; you should never experience brake fade. Disabling this feature maintains the pedal's linearity and enjoyable feel throughout an entire 45 minute track session.

To disable, set to "nicht_aktiv".

Hydraulic Brake Assist (HBA)

N55 X1 Parameter: e84_HBA
N54 335i xDrive Parameter: HBA_DXC_8
In the event of an emergency braking maneuver, the average driver does not brake hard enough to sufficiently stop the car. Thus, BMW implemented hydraulic braking assist. This feature monitors ground speed, brake pedal pressure, and rate of deceleration to understand when the car is in an emergency braking situation. It then increases pressure up to the threshold of ABS to assist the driver in stopping safely. Once again, on the street this is a good idea. In Cincinnati, there is utter carnage on the highway whenever the slightest rain falls. The Ohio River runs red with blood from traffic accidents, and the roads look like a battle scene from Game of Thrones. Implementing an additional safety feature such as this probably helps most people, but on the track it is a disaster. It ruins your ability to brake hard and quickly, assuming the end of each high speed straight is an impending accident. Disable this feature for a super-linear pedal that will require noticeably more effort towards the end of the pedal travel. Be careful with this on the street the first few times you use it - you will find that it activates more often than one would expect. You will have to use a bit more braking pressure towards the end of the pedal than you are used to, but you will be rewarded with a wonderful, linear feel.

To disable, set to "nicht_aktiv". You can also set three levels of assist; "wert_01", "wert_02", and "wert_03". Default value is "wert_03".

Brake Standby (EVB)

N55 X1 Parameter: e84_EVB
N54 335i xDrive Parameter: EVB
This is another ridiculous feature that works well on the road, but terribly on track. If your car detects an aggressive throttle lift-off, it will pre-tension the brakes in anticipation of a hard braking maneuver. This would actually be great if it wasn't for what it does next - if you don't brake within 8 seconds of throttle lift-off, it un-tensions the brakes. I have a theory that people who think they are experiencing pad knock-back on the track are actually just being victimized by this "feature." Turn it off for a more consistent brake pedal that responds predictably.

To disable, set to "nicht_aktiv".

Maximum Brake Support (HVV)

N55 X1 Parameter: e84_HVV
N54 335i xDrive Parameter: HVV
This feature alters the front/rear split of the ABS braking system under emergency braking. At threshold braking when the front tires get into ABS before the rears lock, maximum brake support will increase the brake pressure on the rear pistons to equalize with the front. In theory, this reduces stopping distance. On the street, it probably does - particularly when the car has a heavy cargo load. On the track, it can upset the balance of the car and reduce reaction time. During threshold braking, sometimes one activates ABS accidentally and quickly backs off; maximum brake support will interfere here and get you "stuck" in ABS for a second or two. I recommend turning this off on the track, but it does not have as big of an impact as the other settings do.

To disable, set to "nicht_aktiv".

Dynamic Performance Control (FDB)

N55 X1 Parameter: e84_FDB
N54 335i xDrive Parameter: FDB
This feature encompasses two things - corner braking designed to "torque vector" and redirecting the power through the xDrive system for a 20/80 FWD/RWD torque split. I am conflicted on this option, and need to do more testing on the implications. Without a doubt, this feature accelerates brake pad wear - if you are driving with a decent amount of slip angle, it will be almost constantly corner braking. Traditional logic holds that corner braking is a worse way to torque vector than mechanical LSDs are and that's probably still true, but recently supercars such as the McLaren 650S started coming with corner braking torque vectoring. Granted, the software in a McLaren is hopefully more advanced than that in an entry level sedan (BMW 335i) but the point holds - there must be something to it if supercar manufacturers are going in that direction. What is frustrating about the X1/335i is that you can't separate the 80% RWD bias (an unquestionably good thing) from the brake-based torque vectoring (possibly a bad thing)? So, what's the upshot? I think it probably goes something like this:
1. Base car without this option - code it on for a nice performance boost!
2. M-sport pack that comes with it enabled, but no mechanical LSD - leave it on
3. Car with an upgraded mechanical rear LSD - ?????
I will experiment more with this feature, but my gut says that with a mechanical LSD installed in the rear, having the 80% RWD split will outweigh the drawbacks of the corner braking in terms of lap time.

To disable, set to "nicht_aktiv".

Electronic Differential (AX_Ref_Diff_Lock)

N55 X1 Parameter: e84_AX_Ref_Diff_Lock
N54 335i xDrive Parameter: AX_Ref
Let's be honest, this is really why you're reading the blog. Everyone who has installed a mechanical limited slip differential wants to disable the rear electronic differential. This option is similar to the X1s "Dynamic Performance Control," but on a more basic level. The premise is that with an electronic differential, your BMW will brake the spinning wheel to send torque to the wheel with traction. The problem is, this isn't a very good torque transfer in terms of mechanical efficiency. Installing a mechanical limited slip differential such as a Wavetrac (my choice) in the rear will allow you drastically better traction and mid-corner adjustability. The problem is, unless you disable this e-diff it will be fighting the mechanical LSD and never really allow your actual differential the freedom to do it's thing. If you have a mechanical LSD installed, do yourself a favor and disable this. If you don't have a mechanical LSD, leave it on. At least, until you immediately run out and buy a real LSD (you should).

To disable, set to "nicht_aktiv".

Here is an example of what the stability control module coding looks like in the program NCS Dummy. There are many more options than I have identified here, but I believe I have highlighted everything that has an impact on performance driving.
27069


Turning all of these options off gained me about two seconds on a 1:45 second track. More importantly, it made my car extremely fun to drive.
 
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KevinC39

Corporal
Jun 27, 2017
150
I've had that page bookmarked and in an open tab for awhile now. I was just hoping to not have to get out the laptop and use any ista, inpa, etc as I've never used any of it and am unfamiliar with how to set it up, what software does what, translating languages....
I guess I'm going to have to figure it out eventually and actually spend some time reading up on all of it.

I'm not a track guy so I'm not sure how much some of the brake stuff I would notice. I just didn't want both LSDs fighting each other
 

Torgus

Captain
Nov 6, 2016
1,033
Boston
I've had that page bookmarked and in an open tab for awhile now. I was just hoping to not have to get out the laptop and use any ista, inpa, etc as I've never used any of it and am unfamiliar with how to set it up, what software does what, translating languages....
I guess I'm going to have to figure it out eventually and actually spend some time reading up on all of it.

I'm not a track guy so I'm not sure how much some of the brake stuff I would notice. I just didn't want both LSDs fighting each other
I just downloaded the protools android app and did it from my phone. Super convenient. If anyone local has protools they can do it for you. It is not vin locked or anything.
 
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Reactions: KevinC39

KevinC39

Corporal
Jun 27, 2017
150
I just downloaded the protools android app and did it from my phone. Super convenient. If anyone local has protools they can do it for you. It is not vin locked or anything.
Awesome, that's exactly what I was hoping to hear. I may do injectors soon so I already had protools downloaded but hadn't paid for anything or even plugged it in to the car. Glad to know it can do this too. Thanks.
 

tsaulsbu

Lurker
Mar 16, 2017
18
The previous owner of my car had eBay coilovers on the car when i bought it that are similar to BC coilovers. I checked the rear shocks and they're not shot so i figured they weren't the problem. You think it could be the coilovers?
I would try swapping the rear coilovers and try running more air pressure in the rear tires. My brother's e92 had similarly horrible wandering issues. We swapped in poly subframe bushings, and that helped some. But ST coilovers w/ new shocks yielded the most drastic improvement.
 
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