[johnung]

Curious if anyone has installed a Front Strut Brace on their F30 and what their experience has been. The strut brace is essentially a bar that goes over the top of the engine and connects the tops of the two shock towers to eliminate any flex at the top of the suspension especially during cornering.

I've already upgraded shocks, springs and sway bars. In my older German cars I have also added a Front Strut Brace and it has really tightened things up. I'm curious if it will have the same noticeable effect with the F30 because the chassis is probably already pretty stiff as designed.

Of the photos that I have seen I am most impressed with the front bar from the German brand Wiechers. It comes in either aluminum or in carbon fiber wrapped aluminum. It looks well designed because it isn't a "fixed" design. It has a threaded rod at each end of the center bar with a nut to adjust and fine tune the exact distance between the two shock towers. It's very similar to another German made bar that I installed in the mid-80's. I've included a photo of the bar and another photo that is a closeup of the end that shows the large adjustment nut that I have referenced.

Any opinions or experiences are very much appreciated. Thanks.
John

[FaRKle!]

Yup. I have the KC design. The front end is more composed when cornering and steering feel increased a bit.

[sspade]

Yes.

Do not get a hinged bar, however!

Get a one piece, welded design.

The hinged ones are NOT as rigid and therefore NOT as effective.

I have the OBX Racing Sports bar. Was about $120 all in.

[Logicoeur]

Originally Posted by sspade

Yes.

Do not get a hinged bar, however!

Get a one piece, welded design.

The hinged ones are NOT as rigid and therefore NOT as effective.

I have the OBX Racing Sports bar. Was about $120 all in.

Have some photos of what this hinged version looks like?

[Billfitz]

How much effect an additional brace will have is debatable. I say additional, as the car already has one. It's not obvious, as it's behind the engine, underneath the windshield cowling.

[T5viggen]

Originally Posted by Logicoeur

Have some photos of what this hinged version looks like?

The pictures the OP posted is a hinged design. You can see where the cross bar attaches to the mounting part with a bolt that is going through a sleeve. That allows it to move/flex.

[Logicoeur]

Originally Posted by T5viggen

The pictures the OP posted is a hinged design. You can see where the cross bar attaches to the mounting part with a bolt that is going through a sleeve. That allows it to move/flex.

Ok that's what I thought, thanks. I haven't seen any for our cars that don't use this kind of hinnge however

[sspade]

OBX Racing Sports
Ultra Racing

Are the two brands that Im positive are making one piece, F30 bars... There are probably more as well.

[FaRKle!]

Originally Posted by sspade

OBX Racing Sports
Ultra Racing

Are the two brands that Im positive are making one piece, F30 bars... There are probably more as well.

KC Design's is one-piece too.

[johnung]

Originally Posted by sspade

OBX Racing Sports
Ultra Racing

Are the two brands that Im positive are making one piece, F30 bars... There are probably more as well.

I'm not sure why the assumption is being made that what is being called a "hinged" design has room to flex or move, and as a result it's being judged as an inferior design.
Please see the photo above in my original post as a visual to what I'm about to describe.
This "hinge" is a connection between a rigid bar and a solid welded bracket. The bolt hole in the bracket fits the bolt perfectly so there is zero movement or flex at that connection point. The bolt is an aircraft style fastener sized to handle those forces.

The beauty of this design, which is more expensive to manufacture, is the threaded extension at each end of the crossbar. It essentially allows very minute adjustments to the length of the crossbar which is then fixed in place by tightening the large nut at each end.

This has two advantages. First, during the install with car on a flat surface and the shock tower brackets already installed and torqued to spec, the crossbar is installed and adjusted to the exact resting distance between the shock towers. So during cornering this is always its reference point. Second, during engine servicing the crossbar is easily removed by a single bolt at each end instead of having to remove and re-torque all of the top shock tower bolts.

Way back when I was considering my first strut tower bar a race car mechanic told me to look for this type of "hinged" design. Obviously quicker to work on, he said. But he also said that the distance between shock towers varied slightly car to car. So one-piece bars sometimes have slightly oversized holes for the top shock tower bolts so there is some wiggle room during installation. From an engineering standpoint the forces that might cause any flex in the system are going side to side on those bolt heads, (a task that BMW design engineers didn't size them for.)

With the "hinged" design that force is higher up on the threaded bar core and the bolt attaching it to the bracket, which are both sized for the job. They wouldn't be able to sell a more expensive design if it didn't perform as well or better than the cheaper alternatives. Hope this helps and adds to the conversation.

[sspade]

Its pretty simple...

A one piece, welded design is stonger and more rigid than one put together with a bunch of fasteners.

The fasteners could be made from Tungsten. Irrelevant.

[zole2112]

Install your hinged bar then weld the hinges, I think I'll do that!

[BMWILUVU]

BMW F30 has strut bars extending from the firewall and struts near the front of the engine compartment. The F30 is solid and I can attest from on-track experience. Any improvement from a single hinged strut tower bar is all in your head.

[johnung]

Originally Posted by sspade

Its pretty simple...

A one piece, welded design is stonger and more rigid than one put together with a bunch of fasteners.

The fasteners could be made from Tungsten. Irrelevant.

Yes, there are merits to your last statement, but that wasn't the original point. To paraphrase, the original point was that the "hinged" design was too weak for the particular application and as a result caused flex and movement. The original point was not that a weld was stronger than a fastener. In my opinion, the "hinged" design is not too weak for the application.

I've got a motorhead friend since high school who makes my head spin with these types of discussions. Don't ever ask him why a certain bolt was used on an engine unless you have plenty of time and at least a six pack. He's an experienced welder whose day job happens to be as an R&D design engineer for big aircraft jet engines. He always starts with the specific application and exactly what the minimum strength specs must be in all directions. Then he narrows down the materials and methods that meet that spec and their relative costs towards making a decision on what to use.

He'd probably say that the one-piece welded design and the multiple piece "hinged" design both meet the initial strength criteria to do the job effectively. Then the conversation would be about factors in choosing one design over the other. Like I said, conversations best had over beers! I'm buying the first round. Take care!

[mode.grau]

Originally Posted by johnung

Yes, there are merits to your last statement, but that wasn't the original point. To paraphrase, the original point was that the "hinged" design was too weak for the particular application and as a result caused flex and movement. The original point was not that a weld was stronger than a fastener. In my opinion, the "hinged" design is not too weak for the application.

I've got a motorhead friend since high school who makes my head spin with these types of discussions. Don't ever ask him why a certain bolt was used on an engine unless you have plenty of time and at least a six pack. He's an experienced welder whose day job happens to be as an R&D design engineer for big aircraft jet engines. He always starts with the specific application and exactly what the minimum strength specs must be in all directions. Then he narrows down the materials and methods that meet that spec and their relative costs towards making a decision on what to use.

He'd probably say that the one-piece welded design and the multiple piece "hinged" design both meet the initial strength criteria to do the job effectively. Then the conversation would be about factors in choosing one design over the other. Like I said, conversations best had over beers! I'm buying the first round. Take care!

I'm quite late to this threat (2 years haha) but I think I can provide some input. For context, I'm a final year Civil Engineering student weeks away from graduating, so hopefully I can give some peace of mind in this argument to anyone reading it in the future.

Simply put, if you look at the car from the front, a hinged design would not resist any side-to-side swaying forces. The hinge would not transfer any "swaying forces" (as we call it, bending moment) between the brace and either strut tower. That being said, it would still provide structural resistance against the strut towers from either bending inward toward each other, or outwards away from each other.

An analogy that might make it easy to visualize is a picture frame. Imagine the picture frame's corners are fastened with hinges. While the top left and top right corners would be well-braced from crunching towards each other or moving away from each other, the picture frame would easily sway to the left or right as a whole system, with little-to-no resistance.

I'm not quite sure how the structure in the F3x body behaves. If the intension of the brace is to prevent the inward-outward behaviour, then a hinged design would do just fine. However, if the necessity of the brace is to make the entire front end more rigid from all forms of bending and swaying, the welded/fixed design is far superior.

I hope my explanation was clear

[Billfitz]

Well, there's hinged and there's hinged. Someone would have to confirm it, but the picture appears to show hinged pieces to allow easy installation, but once the bolts are all tightened there's no flexing at the joints.

[johnung]

Originally Posted by mode.grau

I'm quite late to this threat (2 years haha) but I think I can provide some input. For context, I'm a final year Civil Engineering student weeks away from graduating, so hopefully I can give some peace of mind in this argument to anyone reading it in the future.

Simply put, if you look at the car from the front, a hinged design would not resist any side-to-side swaying forces. The hinge would not transfer any "swaying forces" (as we call it, bending moment) between the brace and either strut tower. That being said, it would still provide structural resistance against the strut towers from either bending inward toward each other, or outwards away from each other.

An analogy that might make it easy to visualize is a picture frame. Imagine the picture frame's corners are fastened with hinges. While the top left and top right corners would be well-braced from crunching towards each other or moving away from each other, the picture frame would easily sway to the left or right as a whole system, with little-to-no resistance.

I'm not quite sure how the structure in the F3x body behaves. If the intension of the brace is to prevent the inward-outward behaviour, then a hinged design would do just fine. However, if the necessity of the brace is to make the entire front end more rigid from all forms of bending and swaying, the welded/fixed design is far superior.

I hope my explanation was clear

Welcome to the conversation. You make valid points. I have had many similar conversations with engineers on this subject and on others. The context of the conversation is extremely important. There are two examples that may illustrate this.

First, say we are a race engineering team discussing the best one off strut brace design for our car. All of the points that you made would be very important. We would probably design and weld up a single piece strut brace whose end brackets perfectly match the angles of the tops of our strut towers, and whose crossbar perfectly clears the top of our engine without hitting the underside of the hood. We would hand that strut brace to our experienced race techs to install and manage as part of the race car effort going forward.

But say that the second context is of a product engineering team who is discussing the best strut brace design to be mass produced and sold to a large variety of owners, installed on a variety of F3x models that are used in a variety of daily driver situations and maintained by people with a wide variety of knowledge, experience and tech skills.

These added criteria create more engineering issues. The first is Fitment. Now BMW is a very precise engineering company. If our strut brace were installed the moment each car exited the BMW assembly line, we could design a strut brace with fixed angles on each end because every car would be identical.

But we cannot control at what point in a car's life our strut brace is installed or what that car may have experienced prior. So if there was any sort of collision or bad pothole or anything that could have altered the original angles/position of the strut towers, then our strut brace would not fit properly.

The second added engineering issue has to do with maintenance. A strut brace is added over the top of an engine so it must be removed to perform many common maintenance procedures. A one-piece strut brace would require a minimum of six stock BMW bolts to be removed from the tops of the strut towers to remove the brace. It is a much cleaner solution if only a single bolt needed to be removed from each end of the strut brace.

Engineering is often about simplicity. Design something with less parts that a human being needs to touch to maintain the product, and that's usually the best design.

The third and most critical added design issue to contend with are the function and composition of those stock BMW strut tower bolts themselves. They perform a critical safety function keeping the front suspension intact, so it's important that they are installed and torqued correctly.

On my car they are M10 stretch bolts that must be tightened to 41 ft-lb (56 Nm) and then turned another 90 degrees. They are designed as single use bolts and BMW requires them to be replaced each time. It would cost about $24 to run down to my local dealer to replace my stretch bolts, and $20 if I thought ahead to buy them online when ordering other parts.

Designing a product to be used and installed by thousands of different people doesn't just mean writing down the instructions and saying "Oh well, if instructions aren't followed that's the consumer's problem." It's important in the design to make it as foolproof as possible. That literally means that if a fool buys your product, you try to engineer out them getting themselves in trouble as much as possible. In the end it would cost the manufacturer anyway, in Customer Service calls/emails and even potential lawsuits.

In the case of strut brace bolts it's likely that the torque spec and stretching them by 90 degrees would be followed the first time that the bar is installed. But it's unlikely that every mechanic who removes it subsequently for maintenance will bother to look up the spec and torque them properly. As for replacing the single use bolts, it's unlikely that anyone, except for the most fervent mechanic, will replace them.

So if an engineering team designed a one-piece strut brace, over time it is likely in common use that the strut tower stretch bolts would become degraded by removing and reinstalling them many times over. And it's likely that those bolts will be driving around most of the rest of their life tightened to the incorrect spec.

Both are safety hazards that could be engineered out by designing a multiple piece strut brace where the brackets on top of the strut towers are installed once, with no reason to remove them unless the strut itself needs to be replaced.

The moveable hinge design has the benefits that we have discussed: perfect fitment to whatever angles currently exist at the tops of the shock towers and the ability to easily remove the crossbar for service without disturbing the single use stretch bolts.

As Bill pointed out, with a multi-piece strut brace design, once the bolts at the hinge points are tightened, then it ceases to function as a hinge and functions in the car the same as a single-piece strut brace.

It's pretty cool to have these sorts of engineering discussions. I really find it helpful to think of a design first in a one-off racing context, what's the best possible way to functionally design this piece? And then modify that design with the idea of making it "foolproof" as a product that works in a variety of situations.

I also think that the best engineering comes out of a collaborative team approach, even if one engineer is the lead. It's been proven time and time again that with groups comes a lot of creative power. Fun stuff!

[XxThe_RemedyXx]

I have a Racing Dynamics bar... Very nice quality.

[thejeremyman9]

FYI, there's a way more detailed discussion here: https://f30.bimmerpost.com/forums/sh...3#post27373443

I posted about my install here: https://f30.bimmerpost.com/forums/sh...&postcount=233

Originally Posted by mode.grau

I'm quite late to this threat (2 years haha) but I think I can provide some input. For context, I'm a final year Civil Engineering student weeks away from graduating, so hopefully I can give some peace of mind in this argument to anyone reading it in the future.

Simply put, if you look at the car from the front, a hinged design would not resist any side-to-side swaying forces. The hinge would not transfer any "swaying forces" (as we call it, bending moment) between the brace and either strut tower. That being said, it would still provide structural resistance against the strut towers from either bending inward toward each other, or outwards away from each other.

An analogy that might make it easy to visualize is a picture frame. Imagine the picture frame's corners are fastened with hinges. While the top left and top right corners would be well-braced from crunching towards each other or moving away from each other, the picture frame would easily sway to the left or right as a whole system, with little-to-no resistance.

I'm not quite sure how the structure in the F3x body behaves. If the intension of the brace is to prevent the inward-outward behaviour, then a hinged design would do just fine. However, if the necessity of the brace is to make the entire front end more rigid from all forms of bending and swaying, the welded/fixed design is far superior.

I hope my explanation was clear

Say that it wont resist the "swaying" forces is a bit of a misnomer as it certainly will, although an argument can be made that a solid bar may resist these "better". Also note that the OEM brace that goes to the firewall more or less already serves that purpose.

Additionally, if you consider the forces exerted on the strut tower from the suspension the primary direction is up/inward - i.e., what you call the "strut towers bending inward toward each other". So in this case, the left-to-right strut brace does exactly what it is supposed to.

I went with a specific hinged design for one reason only - so that it can be preloaded. I feel this is a often overlooked design choice and an important considering to make this component as effective as possible.

[auburnf30x]

Well, I ordered one after reading this thread and others. I wasn't sure about it either seeing as how it already has one, but reading other's comments about stiffening up the front end brought up a lot of things I have noticed that supposedly improve after the install, low speed direction changes, body flex on inclines, slight dash creaking during this flex, etc...

I already like the way mine drives as it is, but I will say in those circumstances I have noticed more flexing than I would expect, and could appreciate a tighter response. So we'll see. I go in expecting very little, but will update after the install. My expectations are that it will improve the daily "feel" of the car, but offer very little in actual performance improvement. Should that be the case, it would still be worth it for me.

[Eschmacher]

I installed a megan racing strut bar yesterday, there is a noticeable difference in chassis rigidity.

[auburnf30x]

Received my Megan Racing strut brace today. My thoughts and notes...



Naturally, this brace is known in the state of California to contribute to cancer, homelessness, and the proliferation of feline AIDS, so please proceed carefully with this in mind.



Installation was fast and easy, total of about ten minutes. Most of that was spent getting the protective plastic off. Many people have noted that they didn’t have to remove or modify the ECU cover on their N20/B58, this does not appear to be possible on the B46/48. Someone PLEASE correct me if I’m wrong, but I believe these covers are just cosmetic, so I’m going to leave mine off until I get the time to trim it to fit as neatly as possible.

The good: YES, the difference is noticeable. Largely in road feel. I’m not entirely sure why it makes such a difference, but the brace does help alleviate the criticized numbness in the F30 steering. It definitely feels more ‘alive’ and communicative than before. I do notice some improvement in rigidity, namely when entering incline changes at an angle there is less of that side to side ‘wobble’. It does feel like the car rolls less, but I think that’s just a perceived effect from the wobble reduction and improvement in steering feel rather than an actual reduction in body roll. Overall, the car feels somewhat more planted and confident.

The neutral: I don’t feel that ‘handling’ has really improved any. I put that in quotes because yes, the way it FEELS when pushed is definitely better. I don’t think, though, it makes any quantifiable improvement in the car’s cornering capabilities, other than the increased feedback and confidence it may give the driver from improved feel.

I also don’t like that I have to modify my ECU cover, but Megan Racing explicitly warned that this would need to be done, so not really a negative point.

The bad: That’s not all that will need to be modified.



More noticeable than, and negatively distracting from any improvements in steering feel was this obnoxious light rattle, present only at and just off idle. On the main engine cover, there is a flange over a harness that vibrates very closely to the bar. It will need to be trimmed. This is actually much less significant than the ECU cover and won’t need much to be trimmed...but it wasn’t mentioned, and I really don’t like cutting my car.

Overall, good and worth doing for the improvement felt in the wheel. Just be aware, if you have a B46/48 some cutting will be required.