[The Nightman]

E90 body is inherently stiffer than the E92, as evidenced by the lack of bracing around the rear wheel wells (even the E90 M3 does not have these braces). However, there is more to gain as the E92 was reported to be "20-25% stiffer than the E90" due to its additional bracing (eg front fenders, rear subframe). With that said, the E90 and E92 M3 more or less have the same bracing so I don't really see a point going beyond that. The E93 is apparently 30% less rigid than the E90, hence the need for additional bracing.

[335i54n]

all the bracing helps but you need solid bushing and spherical bearing also. theres also rear e92 body brace/m3 cusco, front m3 strut and megan bar combo, front m3 custom brace plate/bars. if it works i am in

[rbryantaz]

Originally Posted by 335i54n

all the bracing helps but you need solid bushing and spherical bearing also. theres also rear e92 body brace/m3 cusco, front m3 strut and megan bar combo, front m3 custom brace plate/bars. if it works i am in

Someone should take a wrecked e90 and cut the entire bottom body pan out of it and then bolt and weld it over the body of their car making it 2x as thick where the flex is.... Then perhaps with that people will think it is stiff enough!

Sadly I once actually heard of something similar being done for the firewall of an 80s car that wasn't stiff enough (the car actually had two firewalls) to cheat at a track testing event... Firewalls are much lighter than the body though.

-Rich

[GnomeChild]

Originally Posted by Guy Fieri

E90 body is inherently stiffer than the E92, as evidenced by the lack of bracing around the rear wheel wells (even the E90 M3 does not have these braces)

To clarify, the e90 M3 came with the thrust bracing, but not the e93 rear subframe bracing. It did come with bracing, but just some. I would know, the K frame I pulled for my LSD swap was out of an e90 M3 and it did indeed come with the front thrust braces. The only bracing that did not come on all M3s is the e93 specific rear subframe brace.

[The Nightman]

Originally Posted by GnomeChild

To clarify, the e90 M3 came with the thrust bracing, but not the e93 rear subframe bracing. It did come with bracing, but just some. I would know, the K frame I pulled for my LSD swap was out of an e90 M3 and it did indeed come with the front thrust braces. The only bracing that did not come on all M3s is the e93 specific rear subframe brace.

Correct. I retrofitted the M3 mid-chassis to rear subframe bracing to my E90 and it made a significant difference. I assume the additional E93 M3 specific rear brace is not necessary on the E90/E92, otherwise BMW would've made it standard across the M models. Again, the E93 is significantly less rigid hence the need for additional bracing. It even has bracing behind the rear seats IIRC

[GnomeChild]

Originally Posted by Guy Fieri

It even has bracing behind the rear seats IIRC

You shouldn't have told me that

[CalvinNismo]

Guy Fieri are you referring to the bracing plates on the interior that are behind the seats at the front of the boot/trunk behind some trim?

Do you know if the E90 has the threaded lower point? The E91 does not, so maybe this section of the E90 chassis is common with the E91?

GnomeChild the behind the rear seat bracing of the E88/E93, is convertible specific, there are no mounting provisions on the non-convertibles to my knowledge. You’re better off with a Slon wall or something like that.

[feuer]

Originally Posted by GnomeChild

You shouldn't have told me that

They are triangular shape plates that go above the wheel wells right behind the seats. They are there on all m3 I think and are direct fit on none M cars for the most part. M3 had different bushings all around, stiffer springs and none Run Flat tires. So many different reasons for these plates. https://www.e90post.com/forums/showthread.php?t=1838569 To thin to do much in regards to chassis stiffness.

[GnomeChild]

Originally Posted by feuer

https://www.e90post.com/forums/showthread.php?t=1838569 To thin to do much in regards to chassis stiffness.

I still like these a lot. Maybe the best part about it is how it will tuck away behind the trunk liner and be completely invisible. A dedicated aftermarket cross brace would probably be more effective but would probably signal to everyone that my priorities may not be in order and that I spend too much on my car. Plus it would surely interfere with the use of my fold-down rear seats I spent nearly $1000 installing a few years ago

I definitely spend too much money on my car but I surely don't want anyone being able to tell just from looking at it

[The Nightman]

Originally Posted by feuer

They are triangular shape plates that go above the wheel wells right behind the seats. They are there on all m3 I think and are direct fit on none M cars for the most part. M3 had different bushings all around, stiffer springs and none Run Flat tires. So many different reasons for these plates. https://www.e90post.com/forums/showthread.php?t=1838569 To thin to do much in regards to chassis stiffness.

E90 M3 does not have these braces, suggesting that the sedan is more rigid than the coupes. If it were necessary, I would assume the E90 M3 would have them as well.

I still wanted to retrofit them but unfortunately it's not easy since the E90 doesn't have threaded holes there. The existing holes don't match up to commonly sized rivnuts so you'd probably have to weld a nut in. I didn't pursue it further after finding out the E90 M3 doesn't have them.

[The Nightman]

Originally Posted by GnomeChild

You shouldn't have told me that

[GnomeChild]

Ah yes, I see I see

[GnomeChild]

I did a little digging for some... exhaust related investigations and it seems as though I may have accidentally found our missing bolt in the non-M e93 section...


Curiously, the bolts used to brace the two arms together is the same bolt that is used to mount the thrust arms at the rear
07119905147

I am going to order 4 more and hope for the best. The arms just arrived today so once the brace and bolts get here as well, Ill start" bolting" what I can of it together in the backyard to make sure all the bolts are correct

A bit off topic but I've made a bad decision today and bought a complete N55 midpipe for use in future exhaust experiments and it has a little rod welded to the top of the two exhaust pipes. It essentially connects them together right before the mufflers where the pipes turn inward: might interfere with the e93 brace and possibly even the M3 Diff. I really hope I don't have to cut the little rod....

[GnomeChild]

I think I will sleep with it next to be tonight because despite what you have heard about me, I am in fact that guy. I don't know how I am going to go about finding a comfortable position or keeping my white sheets clean with the thin layer of dirt all over this thing but I am sure I will manage to whisper sweet nothings occasionally during pillow-talk as I gently drift off to bed

I put my order in for all the bolts at ECS last night. The arms came yesterday as well; they're pretty long that's what she said

[rbryantaz]

Originally Posted by GnomeChild

I think I will sleep with it next to be tonight because despite what you have heard about me, I am in fact that guy. I don't know how I am going to go about finding a comfortable position or keeping my white sheets clean with the thin layer of dirt all over this thing but I am sure I will manage to whisper sweet nothings occasionally during pillow-talk as I gently drift off to bed

Nothing like the smell of brake clean in the bed!

Take pictures of the install... I assume it requires a rear subframe drop.

I may have to install mine if it goes well for you.

-Rich

[GnomeChild]

It's going to be a while

Probably long enough that this initial buzz/reception will be completely forgotten

I still have an M3 K frame and driveshaft I need to swap before I do much of anything, but I will probably do at least a mock up while my subframe is off the car and most likely a full instal shortly after if it truly requires a subframe drop to save me some trouble. It is much too cold to be doing any major car work however. Needs to warm up a bit first so a few months at the earliest.

This thread was mostly posted as a proof of concept and is slowly morphing to a DIY... Full DIY with pictures and OP edit can probably be expected. I want it documented so people know it can be done, regardless of the benefits.

[Torgus]

Originally Posted by whyzee125

Nice find, I'm gonna look into this. I recently got solid aluminum subframe bushings and absolutely hate them due to the insane NVH, but would like to keep the reduced slop so these with the M3 bushings may be the ticket for me.

Weird I have zero NVH from my subframe bushings...

[Tambohamilton]

Originally Posted by Torgus

Weird I have zero NVH from my subframe bushings...

I got a noticeable amount just from M3 ones

[whyzee125]

Originally Posted by Torgus

Weird I have zero NVH from my subframe bushings...

I was baffled at first as to how annoying it was when most reviews seem to say NVH is nonexistent, but one guy responded to my thread on it with an explanation that makes sense.

He suspected (and I agree) most people who go solid, are already a good ways down the NVH path, ie camber plates, upgraded diff mounts, single mass flywheel, etc. so it doesn't seem as out of place or as noticeable when there are noises from every part of the car. I've ruled out any issues with my diff, etc. and I got an increase in all 3; noise, vibration, and harshness, but the worse being noise.

My car was as quiet as stock before the solid subframe mounts and it became completely unlivable with the install of them. Interestingly, while many shops like MRF swear by them, some other knowledgeable suspension shops like Harold @ HPA, AKG, and the shop I used to install them, strongly advise against it due to the massive increase in NVH. I'm going back to M3 or Poly.

[Torgus]

Originally Posted by whyzee125

I was baffled at first as to how annoying it was when most reviews seem to say NVH is nonexistent, but one guy responded to my thread on it with an explanation that makes sense.

He suspected (and I agree) most people who go solid, are already a good ways down the NVH path, ie camber plates, upgraded diff mounts, single mass flywheel, etc. so it doesn't seem as out of place or as noticeable when there are noises from every part of the car. I've ruled out any issues with my diff, etc. and I got an increase in all 3; noise, vibration, and harshness, but the worse being noise.

My car was as quiet as stock before the solid subframe mounts and it became completely unlivable with the install of them. Interestingly, while many shops like MRF swear by them, some other knowledgeable suspension shops like Harold @ HPA, AKG, and the shop I used to install them, strongly advise against it due to the massive increase in NVH. I'm going back to M3 or Poly.

What is the noise exactly? Or noises you hear? I am just curious. I 100% believe you. It is just so much different than my experience and I have written like 20 times on these forums zero NVH.

Nothing connects to those bushings. I found it really 'tightened' up the rear end when going WOT. I just don't understand what sound would be generated from them. If you look at the subframe it is not moving. There other arms would still have rubber bushings everywhere etc.

When I did them I was on stock struts, and eibach springs. My suspension was 100% stock otherwise. Granted not much else was

Which bushings did your shop install?

[Tambohamilton]

The subframe bushings isolate most of the rear suspension (everything except shock and spring tops), and half the drivetrain from the body. Anything in the rear suspension or back half of the drivetrain that generates or has a vibration/etc input, that vibration will be transmitted to the body with solid where stock or even M3 will go a fair way towards absorbing it. Of course they transmit more to the body, the exact same as they keep the rear wheels feeling connected for acceleration/handling.

My car has suspension far from stock, and I've even gone to mainly monoball rear suspension too now (after rsfb), but the engine mounts, exhaust, intake are all stock and pretty damn quiet. As YZ says, I think that's why I notice the NVH, where many others don't.

[whyzee125]

Originally Posted by Torgus

What is the noise exactly? Or noises you hear? I am just curious. I 100% believe you. It is just so much different than my experience and I have written like 20 times on these forums zero NVH.

Nothing connects to those bushings. I found it really 'tightened' up the rear end when going WOT. I just don't understand what sound would be generated from them. If you look at the subframe it is not moving. There other arms would still have rubber bushings everywhere etc.

When I did them I was on stock struts, and eibach springs. My suspension was 100% stock otherwise. Granted not much else was

Which bushings did your shop install?

I genuinely appreciate that! It seems to be really amplified road noise/resonance through the cabin. It changed in pitch quite a bit when I switched from Michelin to Continental tires so I think the majority of it's just tire noise that's now being transmitted to the car somehow. Really not sure why it's so much louder in my case than others.

You have the Turner bushings right? The shop (Kadunza in Knoxville, TN) installed Bimmerworld aluminum bushings in my car. They look similar in design but could have different amounts of surface area or something that's causing the difference.

Here's a video at normal highway speed: https://www.youtube.com/shorts/m0L3NVsXTG8