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Of you are going to do use this method, at least do it right. First get a class 10.9 (metric equivalent to grade 8). Then strip the rust off of that plate (I mean c'mon!) and bend it so it actually fits against the trunk floor properly. Then sand the trunk floor and JB Weld the plate to the trunk floor. If done right, it will be nearly as strong as welding the plate on there.
 

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OEM ///PLUS
2003 M3 6MT Slicktop
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As funny and amusing as it may sound, yes it is. I just wanted to share with my fellow fanatics to see if anyone has done it or tried this before.

well see my post #11 above. been done about 8 yrs ago.
 

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I see the drawing on that thread but it doesn't explain how the top bolt ataches to the mount. Either you drill and tap into it or weld something on top of it to screw into. I agree this would reinforce the mount location and could hold up for a while only if there is no significant tearing on the bottom. If there is a hole there and you can see the mount and move it by hand with the car in the air then no way is this fix going to hold.
 

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Here is what I copied from another E46F member, I believe it's the best method.
Notice how the main rectangle tube is cut through and goes down about one inch into the trunk floor. This gets welded to both the bottom & top sheet metal, making for a very rigid platform. Then of course all the other structural material is weld in to tie everything into the shock towers. Take a close look at all the pics, you'll see what I mean.

But like I said, if you're dealing with a small subframe problem that has not yet become bad;............the OP's fix is Stupid Simple. I'm shocked no one has ever done this before now.
 

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Discussion Starter · #27 ·
Thank you all for your opinions and thoughts. I have now actually switched the bolts side and cut the bolt to where i can use the trunk. Ill switch the bolt out later due to the limited time i have to work on this. Ill upload a pic later of the trunk and everything.


Sent from BimmerApp mobile app
 

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Here is what I copied from another E46F member, I believe it's the best method.
Notice how the main rectangle tube is cut through and goes down about one inch into the trunk floor. This gets welded to both the bottom & top sheet metal, making for a very rigid platform. Then of course all the other structural material is weld in to tie everything into the shock towers. Take a close look at all the pics, you'll see what I mean.
Exactly, connecting the two shock towers, so the fix doesn't rely on the weak sheet metal underneath.
 

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snowdogs rule
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Hello BMW Experts!
I really like the way the OP did this. Using JB Weld to hold the new plate in place sounds good also, since it would not weaken the original metal like a weld or sheet screws would.
The only question I see as unanswered is what thread pitch would engage the original mounting threads (the threaded block between the two layers of the floor) while the bolt is passing through?

Murf
 

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If the OP used just a long bolt going from added top plate through the bottom floor and bolted to the subframe bushing, then it is not good. There must be a long spacer tube around the bolt from the added top plate to the bottom floor. The spacer tube prevent the top and bottom floor pulled together when bolting the bushing. Without the spacer tube, eventually the two floors will be moved closer then there is backlash between bushing and floor, then hammering and destruction on the floors.

For the towers connecting rectangular beam method, again is there a spacer tube from the bolt mounting beam to the bottom floor to support the pulling force when tightening the long bolt?
 
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