[GnomeChild]

Has anyone heard of this?

Only heard of a few members doing this brace but I decided I was going to do it too. Basically, all M3s have a thrust brace that is mounted in front of the rear subframe and ties it together with the chassis:



(you can click on the diagram to take you directly to the RealOEM page)

The Thrust brace, represented by #7 is broken into 2 part numbers (left and right) as well as a center brace (not pictured) and is held together by some bolts at position 5 and position 6, part numbers below for the curious:
51618040751
51618040752
18211436309
07119906034 (x4)
07119905147 (x4)


e93 M3s specifically have a second brace that goes over the thrust brace and acts as a subframe brace as well, but from the rear (represented by 1 and 8). I have also been able to narrow down the part numbers to the ones below (reference the diagram to see where the bolts go)
51618045950
51618045987
51618045988
07147203503 (x2)
07119905818 (x1)
07147165618 (x1)


However I've looked everywhere but am unable to find the bolts that actually attach the brace to the subframe (circled in red, there are 2) or the bolts that hold the brace arms together (circled in blue, there are 4). Curiously enough they appear no where in the diagram and I'm having difficulties finding which bolts go there considering this seems like a couple "retrofits" I'd like to do on my e90 to tighten up that rear end. I know I've read of a few members doing this to their cars but has anyone done this recently? Do you mind sharing where the #8 brace actually attaches to the subframe and where I could possibly source the last few bolts I need?


Non-M3 e93s come with a similar not-as-beefy brace, and even e92s got an aluminum (also not-as-beefy) thrust brace, but clearly you can see how stout the whole setup is on an e93 M3 (thrust brace outlined in blue, rear subframe brace outlined in red and tucks right behind the diff). Poor e90s have nothing but a small metal bracket near the resonator so tossing these in the back would probably stiffen things up quite a bit

[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.

[The Nightman]

It's been a while since I went down the M3 bracing rabbit hole, but IIRC, the E91 and E93 chassis had additional mounting points for the extra bracing not found on other models.

[Tambohamilton]

I bet the red bolts are the same as the e91 ones, #8;
https://www.realoem.com/bmw/enUS/sho...diagId=51_6030

[Tambohamilton]

Originally Posted by Guy Fieri

It's been a while since I went down the M3 bracing rabbit hole, but IIRC, the E91 and E93 chassis had additional mounting points for the extra bracing not found on other models.

Funny, I've not spent much time under many e9xs other than my own e91. The only e90 I've been under had the big triangular bracket already bolted to the chassis for the e91 brace...but nothing bolted to it. You could literally have just bolted on the e91 brace

[rbryantaz]

Originally Posted by Tambohamilton

Funny, I've not spent much time under many e9xs other than my own e91. The only e90 I've been under had the big triangular bracket already bolted to the chassis for the e91 brace...but nothing bolted to it. You could literally have just bolted on the e91 brace

I have of part 8 from an M3 that I was going to add to my e90 but never added it....

Unfortunately IIRC the brace bolts to the body of the car and the subframe has to be removed to add it. The wider U connection goes around a channel on the body of the car with a through bolt.

I had the subframe off from the car and re-installed it before I realized this and didn't want to take it off again. I think it may have also required drilling but I don't remember all of the details.

If you need one let me know, it is taking up room in the corner of my garage at the moment and I would be willing to part with it...

-Rich

[GnomeChild]

Originally Posted by Tambohamilton

I bet the red bolts are the same as the e91 ones, #8;
https://www.realoem.com/bmw/enUS/sho...diagId=51_6030

Yeah that definitely looks like it could be it



They are cheap enough that I could take a gamble on them. So far I've added 2 to my cart; if it ends up being those, I'll update the OP with the number

Originally Posted by Guy Fieri

It's been a while since I went down the M3 bracing rabbit hole, but IIRC, the E91 and E93 chassis had additional mounting points for the extra bracing not found on other models.

Originally Posted by rbryantaz

Unfortunately IIRC the brace bolts to the body of the car and the subframe has to be removed to add it. The wider U connection goes around a channel on the body of the car with a through bolt.

I had the subframe off from the car and re-installed it before I realized this and didn't want to take it off again. I think it may have also required drilling but I don't remember all of the details.

I think I do remember some people who've done this mentioning drilling on e90s so yes, it isn't a mod for the most faint of heart. IIRC the two mounting points circled in red in the OP need to be drilled into the chassis to accept the bar. I believe everything else bolts up nicely with existing mounting points. Since I have a whole M3 K assembly sitting for my LSD swap, I'll probably add all the bracing then since my subframe will be down for the swap

Originally Posted by Tambohamilton

Funny, I've not spent much time under many e9xs other than my own e91. The only e90 I've been under had the big triangular bracket already bolted to the chassis for the e91 brace...but nothing bolted to it. You could literally have just bolted on the e91 brace

Interesting... maybe drilling may not be required then? Or maybe it's one of those weird pre-LCI vs LCI things? I'll have to check under my own car one of these days to see what exactly is going on under there

[Tambohamilton]

Could well be a pre-lci thing. The one I've seen was a pre. Worth a check. Personally, I'd be surprised if the holes weren't already there. No idea about the hole for no10.

[rbryantaz]

Note that #7 hits the gas tank on the 335i on the passenger side because it has a sump recess in it that apparently the M3 doesn't have...

If you plan on doing this let me know, I waterjet myself some 3/8" spacers to fix the issue and have a spare set of them. Alternatively there is different version of this brace from another E90 that doesn't have that issue. It is the reverse of this where it has the bars connected to the center brace and then bolts to a different rear support. It also uses a different 2 bolt per side center cross brace (the 335i one has 4 bolts and looks like the brace that I will picture later) that isn't pictured in your diagrams so that is also needed if you use the M3 brace.


This thread also covers the braces in posts 129 and 135:
https://www.e90post.com/forums/showthread.php?t=878426

Here is a good look at the other brace that can be used with no clearnace issues. I do wonder if having just a single rear bolt connection could allow it to move more than the M3 version but it is probably minimal if anything.



The main parts for this are:

33326777637
33326784315
33326784316

Plus hardware.

-Rich

[GnomeChild]

Originally Posted by Tambohamilton

Could well be a pre-lci thing. The one I've seen was a pre. Worth a check. Personally, I'd be surprised if the holes weren't already there. No idea about the hole for no10.

Yeah, mine is LCI and I know around 2009 BMW was cutting a lot of corners to reduce cost because of the global recession/stock market crash. Not huge corners, just really small changes here and there, but if you're around these cars long enough you'll notice the small little tweaks (windshield wipers, netted seatbacks, adjustable seatbelts, just to name a few). I can't picture my car having a random brace with nothing connected but stranger things have happened

Originally Posted by rbryantaz

Note that #7 hits the gas tank on the 335i on the passenger side because it has a sump recess in it that apparently the M3 doesn't have...

Honestly, I was going to SEND IT and hope for the best. I figured the gastank would flex some, right? Although having parts binding at such a critical area with suspension flex might not be the smartest play so maybe grabbing a prefabbed set of spacers may not be bad..

Originally Posted by rbryantaz

Alternatively there is different version of this brace from another E90 that doesn't have that issue. It is the reverse of this where it has the bars connected to the center brace and then bolts to a different rear support. It also uses a different 2 bolt per side center cross brace (the 335i one has 4 bolts and looks like the brace that I will picture later) that isn't pictured in your diagrams so that is also needed if you use the M3 brace.

This thread also covers the braces in posts 129 and 135:
https://www.e90post.com/forums/showthread.php?t=878426

Here is a good look at the other brace that can be used with no clearnace issues. I do wonder if having just a single rear bolt connection could allow it to move more than the M3 version but it is probably minimal if anything.

https://3a663eb0fef48c6d2d60-a88f8eb...0316_x600.webp

The main parts for this are:

33326777637
33326784315
33326784316

Yeah this version was the one I mentioned in the OP about e92s having an aluminum brace. These are actually e92 non-M specific and IIRC they bolt up without binding on the gas tank. Lots of guys run them no problem but the M3 versions just seemed beefier in general so I went with those. All the part numbers for the M3 brace are in the OP, that center bracket you mentioned isn't pictured in the diagram but I did include the part number for it.

[rbryantaz]

Originally Posted by GnomeChild

Honestly, I was going to SEND IT and hope for the best. I figured the gastank would flex some, right? Although having parts binding at such a critical area with suspension flex might not be the smartest play so maybe grabbing a prefabbed set of spacers may not be bad..

The gas tank will flex but there is a sump there for the fuel pump so distorting that probably isn't a good idea.

Send me a PM if you are interested in the spacers and we can work something out. They are nothing special really but did I draw them out in CAD and had them waterjetted so they are nicer than the ones that made from bar stock initially. I also have the longer 10.9 button bolts to go with them.

-Rich

[feuer]

Originally Posted by GnomeChild

Poor e90s have nothing but a small metal bracket near the resonator so tossing these in the back would probably stiffen things up quite a bit

It was not needed on the e90 e

[GnomeChild]

Originally Posted by feuer

It was not needed on the e90

I was wondering if you were going to post here

Maybe so, the e90 chassis is already very stiff from the factory (I think the stiffest out of all e9x generation cars), but even marginal gains are gains, no? I'm out maybe $500 for all M3 brackets and braces front and rear and even if they are marginal gains, they are gains none the less



Here is another close up shot of the e93 subframe brace from a maintanence manual



OooOooOoOOooooo
Are you convinced yet Post?
you need this

[feuer]

Originally Posted by GnomeChild

I was wondering if you were going to post here

Maybe so, the e90 chassis is already very stiff from the factory (I think the stiffest out of all e9x generation cars), but even marginal gains are gains, no? I'm out maybe $500 for all M3 brackets and braces front and rear and even if they are marginal gains, they are gains none the less

Gain weight maybe? E93 has different subframe, on the front too. It’s because of non existent B pillar and the weight shifting in to the rear when the top is down. Same with e92 that have larger door opening relative to e90 thus the brace. Same with e91 due to the added weight high at the rear. I don’t think there will be any noticeable or measurable change other then placebo effect. It wasn’t a huge cost and bmw would have installed this on every 335i e90 at least, if not on 316i if that make sense.

[Tambohamilton]

Originally Posted by feuer

Gain weight maybe? E93 has different subframe, on the front too. It’s because of non existent B pillar and the weight shifting in to the rear when the top is down. Same with e92 that have larger door opening relative to e90 thus the brace. Same with e91 due to the added weight high at the rear. I don’t think there will be any noticeable or measurable change other then placebo effect. It wasn’t a huge cost and bmw would have installed this on every 335i e90 at least, if not on 316i if that make sense.

I see it differently.

[feuer]

Originally Posted by Tambohamilton

I see it differently.

You don’t expect that engineers would value and support that perspective if it would make sense?

[Tambohamilton]

The engineers would have had specific targets for stiffness, NVH, cost, etc. Their goal would be to hit those targets in the most economical way. Also their targets are probably different from what the OP wants. So I think the proposed bracing may have a significant effect, and the end result is probably different from how the car was *supposed* to be.

Whether or not the difference is positive, or can be felt/used by mere mortal drivers...those are different questions.

Personally I like mods which involve retrofitting OE parts, so I'm keen to see how this goes together and what the outcome is.

[GnomeChild]

Look boys

All I know is M3 parts go brrrrrrrrrrrrr skrrrrrrrat pah-pah POW!

I hope my explanation makes sense

[CalvinNismo]

Originally Posted by feuer

E93 has different subframe, on the front too. It’s because of non existent B pillar and the weight shifting in to the rear when the top is down.

This is true for the (I think) 2008 and on non-M E93’s, but the E90, E92 and E93 M3 have the same front subframe for the V8.

Early non-M E93’s had a bolt-on adapter for the front V-braces.

[CalvinNismo]

It’s definitely worth checking you have the mounting points under the sills for the wide ends of the V-bracing before buying stuff.

I know it’s not apples to apples with E9X’s, but I know the chassis legs/front strut towers have different bracing attachment points between my 2012 E82, 2010 E87 and my partner’s 2010 E88. There’s no (front or rear) V-brace mounting points under the sills on the E87 for sure, I will double check the E82, but others have checked on the forum and I understand they weren’t there. There’s no through bolt mounting provisions for the behind the subframe triangle on the E82 or E87 either, but the triangle is there on the E88. Worth checking!

[GnomeChild]

Originally Posted by CalvinNismo

It’s definitely worth checking you have the mounting points under the sills for the wide ends of the V-bracing before buying stuff

That may prove difficult as I have already purchased the e93 specific V-Bracing/Subframe brace and they are being shipped as we speak!

As mentioned before, I do not believe e90s/e92s came with the provisions on the chassis to accept the e93 specific bracing, at least in regards to the V-brace that is meant to reinforce the subframe from the rear. Other members have reported the frame has to be drilled and such this mod may not be for the faintest of hearts. It DOES bolt up however (once all the holes are drilled that is) if reports from other members equipping their e90s with the e93 brace are to be believed.

I am also not surprised to hear it would be a similar case in the 1-Series chassis. Even non-M e93s come equipped with a rear brace, just not as beefy as the M3 version. It would thus make sense why the e88 has provisions/a brace equipped from the factory but the e82/e87 don't. What I do find interesting is the fact that the e87 does not have its own specific rear brace. Even e91s have a brace in the rear most likely to act as reinforcement to the taller rear end/tailgate. Perhaps BMW thought the compact chassis of the e87 could handle the taller rear/tailgate on its own without the need for reinforcement?

who's to say, my knowledge is limited in such cases on even the e9Xs platform; let alone on the 1-Series.

[CalvinNismo]

I hope it all works out for you!

Yeah, E87’s don’t seem to come with the rear tension strut either (mine didn’t), whereas the E81 does. Similar to the E90 in comparison to the E92. Whether or not I agree with feuer that it is because of the shorter A-pillar to B-pillar on the E87 and E90 so they don’t need it, I don’t know. Could it be because the E87 and E90 are the most common variants and the economies of scale savings are the largest? Again, I don’t know.

I will be adding the rear tension strut to the E87 though. I will also try and add a rear tension strut to the E88 on top of (or underneath) the existing E93-like rear V-brace. When pushing on you can feel the scuttle shake in the E88, so it’ll all help.