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      09-25-2011, 09:19 AM   #110
Alpina_B3_Lux's Avatar

Drives: Audi R8 V10, BMW 530d xDrive
Join Date: Feb 2008
Location: Germany

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Garage List
2009 335i  [4.45]
19. M3 strut brace


As you may have read in my previous review (see here: REVIEW: M3 suspension parts & Quaife limited slip differential ), I've been in the game for improving the stock suspension of my 335i for some time. The M3 pieces that have been installed so far have already had a considerable positive effect and made me think of adding another piece that is transferable from the M3 to my car: the strut brace (or tower brace, as it is sometimes called).

Now, you may say "but the 335i already has a strut brace", and you would be correct. However, the brace that the 335i comes with from the factory is rather flimsy: The bulkhead end is just a loose slot in the end of the brace, so it only braces against compression, in extension it is unsecured. Also the standard single bolt attachment at the strut tops will be subject to flex and distortion, whereas the diecast ring arrangment of the M3 item gives a very solid and rigid attachment to the strut top.

Again, you could argue: "Why the M3 part? Isn't there a strut brace from the BMW Performance line as well?" Well, the Performance strut brace still is only a two point brace, just like the OEM one that comes on the 335i. The M3 brace, on the other hand, is a three point brace that also connects the struts to the firewall, and not only with each other. By definition it is therefore stiffer. This V arrangement also gives open access to the engine and maintains pedestrian impact regs clearances between bonnet and rigid parts.


First of all, you will need to order the parts - either from your BMW dealer or through an aftermarket provider. Here's the link to the part catalogue at RealOEM: BMW E92 M3 strut brace installation on 335i

The components look like this:

To make it easier, here's also the list of the parts with their respective part numbers you need:

51617900821 Ring, dome cross-brace, left
51617900822 Ring, dome cross-brace, right
51618044553 Strut brace (you need two of those)
51618045860 Mount for strut brace
51617891281 Covering cap (you need two of those)
51618046445 Stud (two of those) *
51717898374 Stud (4 of those) *
07119904401 Hex bolt (2)
07146954965 ASA-Bolt with circlip (not needed, can be re-used from existing brace)
07146963730 Torx bolt (2)
51717895241 Hex nut (6)
31316769731 Self-locking collar nut (6)

You will have to replace the items marked with an (*) as otherwise the brace will interfere with the microfilter assembly. Item 51618046445 can be replaced with two 07119904401 hex bolts.

As I wanted to avoid any hassle at the time with bolts or nuts that don't fit, I ordered the whole package through Harold at HP Autowerks who has already been of great help in the past. Here's the link for the M3 brace package (which already includes all correct pieces to install it on a 335i):
HP Autowerks / link to shop for M3 strut brace - everything costs around 250 EUR in total.

As I've no problem admitting that I'm not too much manually inclined, I didn't do the install myself (although it probably is rather easy for someone with a bit of skill). I had it installed, as many of my modifications, by Daum Motorsport that did the job very well, as usual. Here's an extensive guide with photos on how to install it: BMW E92 M3 strut brace installation on 335i

Here are some photos of how it looks installed on my car:

View of the engine bay / right tower (see the red arrow):

View of the engine bay / from the front (see the arrow):

View of the engine bay / complete view (see the two red arrows):


After picking up my car from my garage, I took it for a spin on some curvy back roads, and the difference was noticeable immediately. Compared to other modifications, the difference is not probably immense, but I confirm that it has made a marked difference. The intial steering response is much sharper and more direct, and when you're in a bend, even tiny steering inputs result in the front just tucking in even more. It allows you to drive the car with more precision and is, to say it plainly, even more fun to let it rip on some curvy backroads.

Problems / disadvantages?

None at all from my perspective. Of course it is not cheap and you have the hassle of installing it in replacement of the OEM brace - but at least for those like me that are already on the slippery road of multiple suspension modifications it is certainly worth the money.

Audi R8 V10; sold: BMW 335i