Black & Tan 332iT

[Bry5on]

Seems like the vert brace is missing some mounting holes?

Pretty sure those other 4 holes are nearly useless if you have just the diagonals.

I may have ordered a cabrio brace a week ago… it’s taking forever to ship, so at some point I’ll get it.

Also pretty sure I won’t be able to feel a difference, but who knows!

[Obioban]

What was that? I couldn't hear you over the sound of a drill 😬

The existence of the vert brace certainly gives credence to the idea that this is a useful area to brace.

…. curious that the m3 vert didn’t get it…

[IamFODI]

Seems like the vert brace is missing some mounting holes?

What was that? I couldn't hear you over the sound of a drill 😬

[Obioban]

Seems like the vert brace is missing some mounting holes?

[heinzboehmer]

https://www.motorsportparts.nl/bmw/bmw-e46-z4/body/e46-dubbele-tunnelbrug---1-stuk

Been done already, karter16

Oooh, very nice. Thanks for the link.

Any idea on weight? Convertible piece is 0.946 kg according to realoem.

[bmwfnatic]

In case you want to do some more pondering: https://wilhelmraceworks.com/blog/me...ssis-stiffness

I'm currently pondering about the best way to build a similar thing for myself to get data from my car. Would be awesome to be able to quantify these changes instead of trying to feel them out.

About the tunnel brace, I think a plate sandwiched between the stock parts would yield the most gains for the least effort. Boxing the stock parts in would be even better, but that requires welding. Non-M part is likely the best answer though.

https://www.motorsportparts.nl/bmw/bmw-e46-z4/body/e46-dubbele-tunnelbrug---1-stuk

Been done already, karter16

[Bry5on]

I think I used M8x1.25 x 16mm button (and e-torx, because why not make it complicated) head screws, I will have to double check length. Then just M8x1.25 rivet nuts with 2mm ground off the nose so that they’d fully seat into the subframe before hitting the upper wall. Installed wet with POR-15 to prevent rust just in case.

edit: I ordered some of these to test grip range. Will report back: Low-Profile Rivet Nuts, Tin-Zinc-Plated Steel, M8x1.25 Internal Thread, 15.2mm Long

https://www.mcmaster.com/91230A011

Ok this is definitely the right part for this application. Should fit in the available space and installs into a .500” hole

[Bry5on]

What hardware did you use?

I think I used M8x1.25 x 16mm button (and e-torx, because why not make it complicated) head screws, I will have to double check length. Then just M8x1.25 rivet nuts with 2mm ground off the nose so that they’d fully seat into the subframe before hitting the upper wall. Installed wet with POR-15 to prevent rust just in case.

edit: I ordered some of these to test grip range. Will report back: Low-Profile Rivet Nuts, Tin-Zinc-Plated Steel, M8x1.25 Internal Thread, 15.2mm Long

https://www.mcmaster.com/91230A011

[heinzboehmer]

Alright, here’s a link for those in the US where you can purchase this v-subframe brace directly if you so desire: https://cart.sendcutsend.com/styxqbkx1nth

Reminder, this link is not me selling anything, I make no money on this, and I’m not affiliated with sendcutsend other than really liking their service.

What hardware did you use?

[Bry5on]

Alright, here’s a link for those in the US where you can purchase this v-subframe brace directly if you so desire: https://cart.sendcutsend.com/styxqbkx1nth

Reminder, this link is not me selling anything, I make no money on this, and I’m not affiliated with sendcutsend other than really liking their service.

[heinzboehmer]

I was pondering torsional rigidity last night - do you think there would be anything at all to be gained by replacing the 2x transmission/exhaust tunnel brackets with a single torsion plate across those 8x mounting points? Not from the perspective of preventing the tunnel from spreading out /collapsing in but in terms of helping to prevent longitudinal twisting? In theory it would make a non-zero difference, but the two brackets are fairly close together so not sure if there would be much, if anything, to be gained in practice? The non-M3 convertible had a similar sort of thing (although I believe that was only 4x mounting bolts not 8). BMW didn't do that on the M3 vert though so 🤷♂️

In case you want to do some more pondering: https://wilhelmraceworks.com/blog/me...ssis-stiffness

I'm currently pondering about the best way to build a similar thing for myself to get data from my car. Would be awesome to be able to quantify these changes instead of trying to feel them out.

About the tunnel brace, I think a plate sandwiched between the stock parts would yield the most gains for the least effort. Boxing the stock parts in would be even better, but that requires welding. Non-M part is likely the best answer though.

[Obioban]

Ordered a couple

[Obioban]

Thanks!

[Bry5on]

3D file attached as well, by request

[Bry5on]

Here you can see more clearly how I got my bends incorrect. When bent correctly, the holes should be offset right and pretty centered around the subframe drain hole.